PROPOSED SODIUM CYANIDE PLANT Preliminary Risk Analysis€¦ · A Preliminary Risk Analysis has...

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Page 1: PROPOSED SODIUM CYANIDE PLANT Preliminary Risk Analysis€¦ · A Preliminary Risk Analysis has been carried out for the proposed Du Pont solid sodium cyanide manufacturing plant

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ou fl fliJI r uI!J- DU PONT (AUSTRALIA) LTD

PROPOSED SODIUM CYANIDE PLANT

Preliminary Risk Analysis

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PRELIMINARY RISK ANALYSIS

of the

SODIUM CYANIDE MANUFACTURING PLANT

at

KWINANA, WESTERN AUSTRALIA

for

DU PONT (AUSTRALIA) LTD.

TIA

Det norske Yeritas

Report No. 899007.

July, 1989

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CONTENTS

SUMMARY 4

INTRODUCTION 5

2.1 Background 5

2.2 Study Aims & Objectives 5

2.3 General Nature of the Project 6

2.4 Philosophy & Approach to Risk Assessment 7

2.5 Risk Standards and Guidelines B

PROJECT DESCRIPTION 10

3.1 Site Location & Environment 10

3.2 Meteorology 14

3.3 Process Description 17

3.4 General Design Requirements/Considerations 23

3.5 Other Parameters in Surrounds of Chosen Site. 25

FACTORS AFFECTING SITE SELECTION & RISK TO PUBLIC & 26

NEARBY FACILITIES

4.1 Properties of Process Materials 26

4.2 Potential Hazards Associated with Sodium 26

Cyanide Plants 4,3 Review of Safety Record of Similar Facilities 30

4.4 Review of Engineering Codes & Standards 31

4.5 Review of Safety Engineering Design 31

4.6 Domino Effects ' 32

RISK ASSESSMENT 34

5.1. Methodology 34,

5.2 Hazard'Identification . 37

5.3 Event Frequency 44

5.4 Consequences of Failure 47

5.5 Risk of Domino Effects . 48

5.6 Individual Risk Levels 49

5.7 Cumulative Risk Levels 50

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CONCLUSIONS

51

REFERENCES

55

APPENDICES

A Properties of Process Materials B Assumptions made in Preliminary Risk Analysis C Meteorological Data D Du Pont Safety & Occupational Health Policy E DnV Risk Analysis Experience F Ammonia source/release models G Summary of Major Release Incidents H Relevant Computer Printouts I Description of Models/Methods used in Consequence

Calculations. J EPA Guidelines for the Proposal

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1. SUMMARY

A Preliminary Risk Analysis has been carried out for the proposed Du Pont solid sodium cyanide manufacturing plant at Kwinana, Western Australia.

Design capacity of the plant is 45,000 t/a, and feedstock will be liquid ammonia and natural gas, both supplied by pipeline.

Conventional risk analysis techniques were used to identify hazards associated with the plant and a number of failure cases leading to the release of toxic or flammable materials were analysed for frequency and consequence.

Resultant risk levels for the plant have been assessed and compared with risk acceptance criteria adopted by the Western Australian Environmental Protection Authority.

DnV concludes that individual risk from the proposed plant is significantly below 1 x 10 6 per person per year in the nearest residential and public access areas and the assessed risk levels therefore satisfy the EPA guidelines on risk acceptance.

Adding the Du Pont levels to the existing cumulative individual risk levels will result in a small zone above 10 (per person per year) at the plant site. This is no higher than other existing or proposed chemical plants in the cumulative risk study. Risk levels at residential areas should not be affected.

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2. INTRODUCTION

2.1 Background

Du Pont (Australia) Ltd proposes to establish a 45,000 t/a sodium cyanide briquette manufacturing plant at Kwinana, Western Australia.

Du Pont is currently the major importer of sodium cyanide, used primarily for gold extraction, and distributes the packaged product to users by road and rail from Fremantle and Kalgoorlie. Due to the ready availability of the raw materials required to manufacture sodium cyanide, as well as the increasing demand created by the continued expansion of the gold industry in Western Australia, Du Pont proposes to supply the market with locally manufactured, rather than imported, solid sodium cyanide.

A Public Environmental Report (PER) is currently being prepared by Kinhill Engineers Pty Ltd in accordance with guidelines issued by the Environmental Protection Authority (EPA). Det norske Veritas have been commissioned to prepare this Preliminary Risk Analysis (PRA), as required by the EPA.

This PRA has been prepared using guidelines issued by the EPA (Appendix J) for such risk analysis studies and EPA Bulletin 278 (Ref. 30) which concerns risk acceptance criteria proposed for Western Australia.

2.2 Study aims and Objectives

This Preliminary Risk Analysis will be a complementary document to the Public Environment Report, the principal objectives being as follows:

a) A conventional Quantitative Risk Analysis is carried out on the preliminary design in order to assess risks to individuals off-site, particularly in public areas and residential zones.

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These risk levels are compared with risk acceptance criteria, in particular the criteria guidelines set down by the EPA in Bulletin 278 (Ref. 30).

Proposed design engineering and operating systems are

critically examined and recommendations are made, as necessary, on

-. Design codes

- Process design

Operating procedures

- Safety management

with a view to minimising the occurrence or impact of - potentially hazardous incidents.

2.5 General Nature of the Project

Du Pont proposes to construct a sodium cyanide manufacturing plant in a 10 ha site in the Kwinana Industrial Area to produce 45,000 t/a of solid sodium cyanide as briquettes (or compacted crystals).

The plant will utilize proven Du Pont production technology and will use liquid ammonia, natural gas and caustic soda, piped into the plant, as principal feedstocks.

Product will be packed in semi-bulk "bag in a box" containers and steel bins and distributed by road, rail and sea to users in Australia, PNG and South East Asia. The only by-product of the plant is a surplus of process steam.

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2.4 Philosophy of Approach to Risk Assessment

The potential for major hazard arising in the processing, storage or transportation of hazardous materials warrants special measures to ensure safety of the public, the work force and the plant.

One of the approaches utilised in the development and approval of facilities involving products such as ammonia is Risk Assessment, which requires the use of a range of analytical techniques and calculation methods to identify and evaluate the hazards and risks associated with a process or facility.

The primary purpose is to ensure that all significant risks are identified and properly evaluated to enable appropriate action to be taken to eliminate or reduce the potential for serious accident. The techniques, while still subject to many limitations and uncertainties, have developed to the stage where much of the risk can be quantified in terms of consequence, probability or frequency of occurrence and resultant frequencies (risk levels) of exceeding designated hazard impact levels.

Consequently, it is now common for risk assessment to be used to assist in the approval process for new plant proposals. The risks associated with a plant are measured against criteria to assist in determining the acceptability, of the risk for the proposal involved. I

NY It is essential that risk assessment be carried out in an

/ objective manner by competent analysts who achieve a proper understanding of the processes and risks involved. Because some degree of subjectivity exists in assessing failure modes, selecting failure rate data, determining inputs to calculations and computer programs, and so forth, it is also necessary for the assessment to be carried out free from influences which could result in bias. This is best achieved by ensuring independence of the analysts.

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2.5 Risk Standards and Guidelines

2.5.1 EPA Guidelines - General Criteria for Risks Assessment

The Environmental Protection Authority Statement (Ref. 30) on the evaluation of the risks and hazards of industrial developments on residential areas in Western Australia proposes the following as a guide for assessment of the fatality risk acceptability of new industrial installations:

The Authority has taken note of how decisions on risks are taken in other parts of the world. In the light of that knowledge the Authority will classify decisions into three categories. These are as follows:

- A small level of risk which is acceptable to the Environmental Protection Authority;

- A high level of risk which is unacceptable to the Authority and which warrants rejection;

- A middle level of risks, which subject to further evaluation and appropriate actions may be considered to be acceptable to the Authority.

An individual risk level in residential zones of less than I in a million a year is so small as to be acceptable to the Environmental Protection Authority.

An individual risk level in residential zones exceeding 10 in a million a year is so high as to be unacceptable to the Environmental Protection Authority.

Where the preliminary risk level in residential zones has been calculated to be in the range 1 in a million to 10 in a million a year, the Authority will call for further evaluation of the risks associated with the project. The Authority may then be prepared to recommend that the project be acceptable subject to certain planning and technical requirements.

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A major technical requirement will be the commissioning of a Hazard and Operability (HAZOP) Study at the detailed design stage of the project. Such a study is an effective technique for discovering potential hazards and operating difficulties at the design stage. As a result of studies, significant reductions of hazards and the number of problems encountered in operation are possible. The HAZOP Study should be undertaken by the proponent with a qualified person, approved by the Authority, who has to certify to the Authority that the study was carried out in a proper manner. This study should explore all feasible ways of reducing risks. The proponent may also be required to update the risk analysis and make the results public.

2.5.2 Cumulative Risk Impacts

In addition the EPA proposes that cumulative risk effects be considered as follows:

Where a number of hazardous industries or activities exist in a region, it is appropriate for a cumulative risk and hazard analysis for existing and proposed developments in the region to be undertaken before- assessing new developments in the region. No extra risk would be acceptable where the cumulative risk of existing industry, combined with the assessed risk of the proposed new industry, exceeds the risk levels proposed for new industry.

A Cumulative Risk Analysis for the Kwinana Industrial Area was commissioned in 1986 and updated in 1987 and 1988. The original report covered the existing level of risk, covering 14 major industries in the KIA (the 'Base Case'), and the update included 5 additional industrial developments. It is intended that the cumulative risk assessment will be updated periodically to give an overview of the level of risk generated by processing, storage and transportation of hazardous materials to the local population.

Extracts from this Preliminary Risk Analysis will be compiled so that the contribution of the proposed Du Pont plant to cumulative risk can be assessed.

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3.0 PROJECT DESCRIPTION

3.1 Site Location and Environment

A site selection study has been carried out (Ref. 35) to identify the most suitable site for the plant and concluding that the three following sites in the Kwinana Industrial Area (KIA), approximately 30km south of Perth, were most appropriate.

This risk analysis has been carried out for the preferred location site A. (See figure 3.0) The quantified risks will not differ greatly between sites A, B and C, although such factors as changes in the ammonia and natural gas pipeline routes may alter the risk contours.

Site A is located to the north east of the existing nickel refinery and directly south of the CSBP/KNC complex. A pipeline of about 2,0 km will be required for liquid ammonia supply to this site.

A provisional layout for the proposed site is given in Figure 3.1. The site will be approximately 10 ha in area.

From Figure 3.1 it can be seen that Site A is bounded on the north east by the Coogee Chemical Company's tank farm (containing hydrocarbons andsolvets). There will be vacant land to the north west, on the other side of Pioneer Road. Note that the plant site straddles the existing railway line leading to the nickel refinery.. Spurs from this railway line will be built for rail loading from the Du Pont plant.

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The existing pipeline corridor supplying ammonia, hydrogen, syn gas, nitrogen and CO2 to the nickel refinery runs parallel to Pioneer Road.

Vacant land, owned by Western Mining Company, lies to the south west of Site A, and Patterson Road forms the south eastern boundary.

Medina, part of the Kwinana township, is the nearest residential area, about 2.5 km east of site A. The next closest residential zone is East Rockingham, about 2.5 km to the south of the site.

The area around the site is quite flat, with no prominent topographical features. Between the Kwinana Industrial Area and Medina there are a number of sandy ridges, covered with light scrub. These will, to a small extent, act as a barrier for any toxic gas dispersion, although gas dispersion calculations are carried out assuming a flat terrain.

There is a proposal (Ref. 29) to develop the Wells Park - Kwinana Beach area, approximately 1km west of the site, as a recreational area.

The development of this site will involve road access along Kwinana Beach Road, Wells Road and Third Avenue to the west and north of the site. The site is bounded on the east by Patterson Road, a major traffic route.

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0 1 2 km LPG plant

I ..Y Proposed PICL plant Scale

James Point.

Cockburn Sound

Jetty BP refinery

Jetty

plant /4

CSBP Kwmana AGR sodium'! works cyanide plan(/ C,o7 '' (7 PLANT SITE

Jetty

KwinanaBeach/ refiiy

I..'V7/ )>4' F/ /7 East Rockingham

Figure 3.0 KIA PROSPECTIVE PLANT SITES

I

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Pioneer Road

Plant North

WMC NTCKEL REFINERY

32

32

----'---- --'-.-

\\ '

______________ \

3l /

32 !IH 19

III H

Futureservices HLl 1 -I4j

corridor

32

j

LEGEND 1 Caustic storage 2 Cooling tower 3 Demineralized water storage tank 4 Firewater storage tank 5 Pmcess control area 6 Open storage area 7 Equipment storage 8 Container & flobin' loading 9 Vacuum pumps 10 Rotary filter area 11 Nitrogen storage 12 Cyanide solution tank 13 Caustic solution tank 14 Cookianks 15 Evaporation area 16 Flare 17 Water treatment area 18 Waste gas boiler 19 Natural gas area 20 Washwater tank 21 Airheater 22 Absorber 23 Convener 24 Ammonia area 25 Safety equipment storage area 26 Container &r fib-bin storage & rail

loading: 27 Administrative buildmg 28 Parking

29 Changerooms 30 Guardhouse 31 Ammonia storage 32 Evaporation ponds

Patterson Road

0 50m 6==d LJ L-

Scale

11. .5.1

SITE LAYOUT FOR THE PROPOSED PLANT

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3.2 Meteorology

Introduction:

The climate of Kwinana, as for the entire Perth Metropolitan Area, is characterized by mild, wet winters and hot, dry summers.

Average annual rainfall for the area is 772 mm, which occurs predominantly in winter. The maximum annual rainfall recorded was 1,178 mm, while the minimum was 414mm. The Perth area is renowned for large volumes of rain falling in a short time, with a maximum rainfall falling in one hour being 48mm.

n Wind Direction:

Sea breeze/land breezes predominate in the coastal region around Kwinana. During transition between offshore and onshore breeze, south winds frequently occur (9).

The strongest winds blow from the west and occur mainly in winter when storms from the Indian Ocean affect the coast further South. Offshore easterly winds can reach gale force in summer. Average wind speed is approximately 4 m/s from records at Hope Valley Base Station near the plant site.

The wind speed/wind direction frequency matrix for all stability categories is summarised in Table 3.2.1 overleaf.

Atmospheric Stability:

Information on atmospheric stability for Pasquill categories A-F (A=tjnstable, D=Neutral and F=stable) was provided by the E.P.A. from the Hope Valley Base Station for the period 1st January 1980 to 31st December 1980 (11). The information presented is in the form of six wind speed-wind direction frequency matrix tables corresponding to each of the Pasquill stability classes.

From analysis of this information nineteen specific sets of stability categories and wind speeds were initially chosen as representative of the area for calculation purposes. After analysis, sixteen sets were selected as shown in Table 3.2.2.

These categories represent approximately 87% of the time with C,D,4,5 and 7 m/s representing approximately 55%. These may be taken as representing low night-time winds, average conditions, afternoon strong breezes and occasional high winds.

'--S

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TABLE 3.2.1: Wind speed/vind direction frequency matrix for vind data measured at the

Hope Valley Base Station over the period 1st January 1980 to 31st

December 1980. Wind speed and direction were measured at 10 metres

above ground level.

WIND SPEED

RANGE (N/data S)

TOTALS N NNE NE ENE E ESE SE SSE S. SSW SW WSW W WNW NW NNW -------------------------------------------------------------------------------------------------

OVER 13.5 0.0

12.0 - 13.5 0.1

10.5 - 12.0 0.1 0.1 0.1 .0.3

9.0 - 10.5 0.1 0.7 0.5 0.2 0.1 0.2 0.1 0.1 2.1

7.5 - 9.0 0.1 0.1 0.1 0.1 0.1 0.2 2.0 1.2 0.9 0.4 0.5 0.3 0.2 6.4

6.0 - 7.5 0.2 0.4 0.4 0.6 0.6 0.2 0.1 0.1 0.7 3.0 2.8 1.6 1.1 0.8 0.4 0.3 13.2

4.5 - 6.0 0.5 0.8 0.5 1.0 1.8 0.8 0.5 0.8 1.2 2.6 2.7 1.7 1.5 0.9 0.5 0.5 18.3

3.0 - 4.5 0;6 2.0 1.6 1.9 2.5 2.9 2.0 3.5 3.3 2.2 1.4 1.1 1.7 07 0.5 0.4 28.3

1.5 - 3.0 6.6 1.6 3.2 2.7 2.8 3.0 3.3 3.2 2.3 1.4 0.6 0.7 1.1 0.6 0.4 04 27.7

0.5 - 1.5 0.2 0.2 0.3 0.3 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.2 3.4 -------------------------------------------------------------------------------------

TOTALS 2.2 5.2 6.1 6.5 8.0 7.2 6.1 7.9 9.0 12.2 9.5 6.5 6.1 3.9 2.3 2.1 -------------------------------------------------------------------------------------------------

CALMS (LESS THAN 0.5 M/5): 0.1%

The percentages do not add up to exactly 100 due to rounding errors.

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TABLE 3.2.2 Stability Categories & Wind Speeds Used in Report

-----------------------------------------------------------------

Pasquill Stability Category Wind Speed M/S -----------------------------------------------------------------

A - 2,4 B 2, 3, 4 C 4, 5, 6, 7 D 4, 5, 6, 7 E 2,4 F 2, 4

Temperature:

The air temperature (at løm height) varies between 20C and 400C (9), however ground temperatures may be higher. High ambient temperatures will cause rapid vaporisation of any spilled liquids and also result in heating of cold vapour clouds, decreasing density and reducing the rate of gravity spreading. A typical ambient temperature of 22.50

C was used for the majority of the risk analysis calculations.

Surface Roughness Length:

The surface roughness length is a measure of the friction between the atmosphere and the earth's surface. Surface roughness length may vary from less than 1 mm over calm water, smooth ice, or smooth mudflats to over 1 m for the centre of cities. This proposed site and surrounding terrain is a low lying area surrounded by a variety of landscapes and buildings ranging from minor vegetation to large warehouses and chemical plants. Surface roughness is estimated to be in the range of 0.1 to 0.3 m, therefore a length of 0.1 m was chosen as a value which would give reasonably conservative results.

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3.3 Process Description

3.3.1 General Description:

The proposed plant will product 45,000 t/a of sodium cyanide in solid briquette form, and is based on a modified Andrussow process, which involves heating ammonia, natural gas and air together in a reaction vessel to form converter gas with approximately 8% hydrogen cyanide. This gas is passed through a column containing caustic soda solution to produce a sodium cyanide/water solution, which is then concentrated in an evaporator. The concentrated solution is subsequently crystallized and compacted into solid briquettes.

The overall reactions are described by the equations:-

CH4 + NH3 + 1.5 > HCN + 3 HO

methane + ammonia + oxygen ------> hydrogen + water (from air) cyanide

HCN + NaOH ' NaCn + H 2 0

caustic sodium soda cyanide

3.3.2 Material Requirements:

The principal raw material requirements for the sodium cyanide plant Include:

Natural gas (42.45 million m3/a) from the nearby SECWA or WANG pipelines.

Caustic soda (85,000 t/a - 50% basis) from the neighbouring chior-alkali plant or other suppliers

Ammonia (29,000 t/a) via a new pipeline from CSBP/KNC bulk storage.

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Additional raw materials required for a variety of functions include:

nitrogen - for purging steam - for start-up electricity (3 MW) DEA make-up for CO2 stripper

Water requirements will be approximately 710 m3/d (259,000 m3/a).

3.3.3 Process Flow Scheme:

A simplified process flow sheet is shown in Figure 3.2. Preliminary piping and instrumentation drawings (P&ID's), mass balance and other design data of a confidential nature were available to DnV for this study. This confidential information is available for viewing by the relevant authorities on request to the proponent.

In order to produce sodium cyanide in solid form, four processing steps are required:

- The reaction of methane, ammonia and air to form hydrogen cyanide and hydrogen.

- Immediate reaction of the hydrogen cyanide in the gas mixture with caustic soda solution to form a sodium cyanide solution.

- Evaporation of the solution to form sodium cyanide crystals; crystal recovery and drying.

- Mechanical compaction of the crystals into briquettes.

Ammonia is pumped via a pipeline from KNC/CSBP bulk storage to an intermediate feed tank, holding sufficient ammonia for 2 hours operation in the event of loss of pipeline flow.

Natural gas will be supplied from a tap-in to the nearby SECWA or WANG pipelines and stripped of CO2 in a DEA (diethanolamine) system.

Liquid ammonia is vaporized, superheated and combined with heated natural gas in a pipeline. The mixture is filtered and mixed with filtered air supplied by a compressor. This gas mixture enters a converter where the reaction to produce hydrogen cyanide (HCN) gas occurs as the mixture passes over a platinum/rhodium catalyst.

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The temperature of the resulting HCN gas mixture is reduced

from about 1100°C to about 2300C in a waste heat boiler (WFIB) connected to the converter. Steam from the WHB is used in

process operations.

It is proposed to instal a secondary gas containment system around the reactor, wasteheat boiler and pipeline in order to contain the hydrogen cyanide inventory in the event of a credible release from the process. The containment system

will allow the process to be shut down if necessary.

The gas containment system will be maintained under a vacuum so that no fugitive emissions of hydrogen cyanide can escape

to atmosphere.

The dilute HCN gas stream (about 8% HCN) flows to an absorber

column where it is contacted with sodium cyanide (NaCN) solution. containing excess sodium hydroxide (NaOH).... The HCN reacts with NaOH to produce additional NaCN in solution form. The most significant side reaction is the reaction of CO2 in

the gas stream with NaOH to form sodium carbonate (Na2CO3),

which becomes an impurity in the final product.

Gas from the absorber is scrubbed by a demister before it enters a flare stack connected to the top of the absorber and is burned. Sodium cyanide solution, containing about 35% NaCN by weight, is continually pumped from the absorber to a vacuum evaporator (crystallizer) where the solution is concentrated to a slurry containing about 8% precipitated NaCN (about 50% total NaCN). 50% NaOH is continually fed over two sieve trays in the top of the crystallizer to "scrub out" any HCN in the vapour. The NaOH is collected and fed to the

absorber.

The crystals in the slurry are separated and partially dried with hot air in a rotary filter/mixing conveyor system (80-

90% of H20 after dewatering is evaporated). Drying is

completed as the crystals are pneumatically conveyed to a briquette system where they are compacted into 32mm x 32mm x 16mm briquettes. The land area (fins) between the briquettes is removed in a rotary screener and recycled to the

briquetter. Briquettes are cooled to - about 800C in the

screener with chilled air and the product is packaged in

semi-bulk containers. All discharge air streams are

scrubbed in a common scrubber to remove NaCN dust. A purge from the scrubber is pumped to the filter to clean the

screens.

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CO2 Evaporation ponds

A A Air exhaust 31,300 kg/h

Natural gas CO2 Removal

Flare

3,600 kg/h rWashdown

Waste asf water Scrubbing

Treatment

Mixer Converter Caustic

Absorber Vapour Air Air Waste Heater 13,500 kg/h

Boiler Ammonia

3,700 kg/h Filtrate

Air NaCN Vacuum Filtration Briquette 32,700 kg/h solution Evaporator' Crystals Drying Cooling

27,000 kg/h '

Steam

To other parts of plant ' ' 4,650 kg/h

3,000 kg/h

Waier Air

Heater 11,400kg/h

Packang

6.700 kg/h Solid sodium

cyanide bnquettes

Air

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3.3.4 Product Transport:

The finished product will be stored in packaged bag/box form in an on-site undercover warehouse with a storage capacity of 2,800 t. Subject to regulatory approval, transportation for distribution will be either by packaged bag/box containers in the first instance or by steel 'flo-bins'. The bag/box container consists of a woven polypropylene bag with a polyethylene liner, packaged inside a sturdy plywood box for shipment inside a standard 'shipping container. The product will be distributed by road, rail and sea to users in Australia, Papua New Guinea and South-East Asia.

3.3.5 Waste Products and Disposal:

Solid waste will be disposed of by blending It Into the process where possible. Contaminated equipment that is to be replaced will be washed, with neutralizing solution prior to disposal at an approved sanitary landfill site.

Process wastewater will be produced at a rate of 54 m3/d (20,000 m3/a), and will be collected and directed to wastewater treatment tanks. This wastewater will be treated to 1 mg/rn3 free cyanide before being discharged via on-site exaporation ponds.

Plant maintenance washings and 'first flush' rainwater will also be contained and treated as liquid wastewater.

Atmospheric emission sources and rates will be as follows:

Flare - 36,300 kg/h air with some nitrogen oxides and ammonia. Scrubber - 22,700 kg/h air with some ammonia and trace levels of hydrogen cyanide and sodium cyanide. Natural gas fired air heater - nitrogen oxides and carbon dioxide.

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3.3.6 Plant Configuration:

The final plant configuration has not been determined as this will be dependent on the conditions of the selected site; however, the plant will require approximately 10 ha of land, which allows for on-site evaporation ponds.

A provisional layout for the proposed plant site is shown in Figure 3.1. The height of the tallest component of the facility, which is the flare stack, will be approximately 30m.

3.3.7 Workforce:

The construction of the sodium cyanide plant and associated facilities will take fifteen months, and will require a peak temporary workforce of 110 personnel.

A total operating workforce of fifty personnel will be required to operate and maintain the plant. Most of this workforce will be drawn from the local area, although some experts will be transferred from the proponent's Memphis plant to assist with start-up and training.

All work will be carried out on a continuous shift basis.

3.3.8 Process By-Product:

The plant will produce commercial quantities of steam as a by-product, in the vicinity of 11,300 kg/h at 1,200 kPa. It is desirable that a potential user be found to exploit excess steam production and it is also necessary that the plant has a source of' steam to facilitate 'start-up' procedures.

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3.4 General Design Requirements/considerations

Du Pont operates an HCN synthesis process and a NaCN process at Memphis (USA), HCN processes at Orange (Texas) and Victoria, Texas. It is a joint venture partner in an HCN process in France and is currently constructing NaCN processes in Texas City, Texas and in Mexico. Equipment and process steps for the Australian Plant are to be duplications of existing proven equipment and operations where practical.

Safety, health and the environment are to be given top consideration/priority in the design of the facilities, which must meet all existing and emerging Western Australia state regulations and Du Pont Safety Health and Environmental policy.

- Key safety and health design considerations are to:

minimize the presence of HCN, minimize employee exposure to the product, prevent contact of NaCN with acids or weak alkalis, which will liberate highly toxic and flammable HCN gas, provide good layouts to prevent "cluttering" and permit good operating and maintenance access and flow of the various tasks,

ensure new equipment except for the vacuum pumps is not to exceed 85 dBa noise levels. The vacuum pumps will be isolated from surrounding areas, design floors for good drainage and to eliminate slipping. Floors in the NaCN processing (Dry End) building are to be solid concrete to prevent drippage below.

There is to be zero waste water discharge from the site. All waste water will be collected in an evaporation poiid on site. Cyanide (CN) level in water added to the pond is to be less than 1 ppm to insure that any birds or other animals that drink water from the pond are not harmed.

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- The design is to minimize the amount of waste water. Recycle/reuse of water is to be incorporated into the design where practical.

The following are design ground level concentrations for the purpose of calculation of stack heights for "worst case' 3 minute concentrations.

HCN - 0.3 ppm NH3 - 0.83 ppm CN - 0.2 mg/cubic meter

Emission limits for new sources as recommended under EPA Guidelines:

total particulate matter - 0.25 mg/cubic meter

NO x (a) fuel burning heaters - 0.35 g/cubic meter (b) gas electricity turbines - 0.07 g/cubic meter

Co - 2.50 g/cubic meter

Other emission levels will be determined on a case by case basis, utilizing "best available technology".

Western Australia at present does not have specific regulations relating to ground contamination, however the EPA advises •that all ground contamination is to be prevented or treated on a case-by--case basis with substantiating evidence. Water runoff from all process areas is to be contained and drained to treatment facilities and/or through monitoring facilities before discharge.

- NaCN will be packaged in polypropylene bags inside plywood boxes (about 900 kg. per box) or 1360kg. metal lb-bins, subject to regulatory approval.

- Ammonia and natural gas feed-stocks to the plant will be supplied by pipeline. Supplies and packaging materials will be delivered by truck and the product will be shipped by rail and truck. A rail spur to the site will be installed.

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Utility stations (compressed air, steam, 'wash-down" water) will be provided at strategic locations, with a utility station on each dry-end floor.

Fire extinguishers, air masks and other safety equipment will be installed in the process area. Safety equipment

specifications for this project will be firmed during final

design.

Good lighting and a public address system will be installed.

Safety showers will be located at strategic locations.

The design is. to follow Du Pont piping standards and specifications or commonly accepted local standards, which ever are the more stringent.

All vessels are to have access through manway nozzles. Platforms are to be provided at all manway nozzles.

Although future expansion of the process is not anticipated at present, design and layout of equipment will allow for

future expansion.

Ninirñum slopes for piping and vessel walls handling NaCN are:

Powdered faCN - 70 degrees (higher preferred)

Fins . - 60 degrees

Briquettes - 40 degrees

It is proposed to instal a secondary gas containment system around the reactor, wasteheat boiler and pipeline in order to contain the hydrogen cyanide inventory in the event of a credible release from the process. The containment system will allow the process to be shut down if necessary.

The gas containment system will be maintained under a vacuum so that no fugitive emissions of hydrogen cyanide can escape

to atmosphere. The system will be designed to meet EPA

guidelines set for achieving gas containment.

3.5 Other Parameters in Surrounds of Chosen Site

Other factors which may affect risk levels at the Du Pont site are the proximity of a set of pipelines leading to the nickel refinery, a railway track, the adjacent roads and a number of industrial sites, including the neighbouring Coogee Chemicals tank farm. These issues are covered in Section 4.6, Domino Effects..

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4.0 FACTORS AFFECTING THE SITE AND RISK TO PUBLIC AND NEARBY FACILITIES

4.1 Properties of Process Materials

From a review of preliminary process information, the following process materials are of interest in this study.

- Anhydrous Ammonia - Methane (in natural gas) - Hydrogen Cyanide - Sodium Cyanide - Carbon Monoxide

As this preliminary risk analysis is primarily concerned with the impact of the complex on the surrounding environment, discussion of hazardous events will focus on those chemicals which will be present in quantities large enough to cause potential problems outside the site if a release occurs.

Appendix A gives the detailed properties of process materials in the proposed complex: physical and chemical properties, and where relevant, flammability and toxicity data.

4.2 Potential Hazards Associated with Sodium Cyanide Plants

The main hazards arise from loss of containment of pressurised gases or liquids (refrigerated or stored under pressure). Resulting vapour clouds mixing with surrounding air may be dangerous, both from the potential environmental effects of the spreading of toxic materials and also from the possibility of a flammable mixture being ignited.

Principal hazards encountered in sodium cyanide manufacturing plants are as follows:

Releases of ammonia from the supply pipeline, feed tank, vaporizer or associated pipework, which contain liquefied ammonia and could produce high flow rates and dense vapour clouds if a serious failure occurred.

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- Ammonia releases downstream of the vaporizer, where the vapour is still under pressure.

- Releases of natural gas from the supply pipeline, where the gas is at high pressure and releases could lead to the formation of dense vapour clouds.

- Hydrogen cyanide releases from the reactor/absorber system.

- Loss of containment of sodium cyanide leading to contamination of the environment or generation of HCN.

CHEMICAL HAZARDS

See Appendix A for further details of hazardous properties.

1) Ammonia

Ammonia is a toxic and also a flammable material. The TLV of ammonia is 25 ppm. Concentrations of about 1700 ppm are dangerous for a half-hour exposure. It can be smelled at a concentration •of about 20 ppm.

The flammable range of ammonia is 15-28% vol. in air. The minimum ignition energy is 100 MJ, which is high. Ammonia is flammable, therefore, but not readily so.

Vessels containing liquid ammonia where high release rates would result from failure have the highest potential to cause offsite damage as dense clouds of ammonia vapour may be formed.

As the normal boiling point of ammonia is -33.40C, it is

stored either as a refrigerated liquid at -330C and slightly - above atmospheric pressure or at higher temperatures and correspondingly higher pressures.

Sections of the process where ammonia is present as vapour are also examined, although the quantities are generally small compared with liquid inventories and releases are likely to be less dense.

In section 5.5 various possible ammonia release events are considered and in subsequent sections the likely behaviour of resultant vapour clouds is described and modelled as part of the consequence and risk level assessment.

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Ammonia is fully miscible with water. This creates the hazard that if there is water in a vessel containing ammonia vapour, the latter may dissolve, so that a vacuum is formed and the vessel collapses inwards.

Materials of construction for ammonia depend on the operating temperature. While mild steel may be used at ambient temperatures, special steels are necessary at low temperatures to avoid embrittlement.

Ammonia is corrosive even in trace amounts to copper, zinc, silver and many of their alloys. It is necessary, therefore, in handling ammonia to avoid the use of valves and other fittings which contain these metals.

Under certain conditions ammonia can react with mercury to form explosive compounds.

Impurities in liquid anhydrous ammonia, such as air or carbon dioxide, can oausestress corrosion of carbon steel. This is largely inhibited, however, if the ammonia contains 0.2% water and this water content is therefore specified for some applications. Stress corrosion is also completely inhibited at -330C-. -

11) Methane

Methane is not stored on site but is present as the principal component of the natural gas feed.

A release of methane may result in the formation of a dense

cloud, as sudden reduction in pressure will result in cooling of the gas and surrounding air. Low pressure or relatively slow release will not involve this cooling, the gas will be lighter than air and will dilute below flammable concentrations more rapidly.

Methane is not toxic except as an asphyxiant. It is flammable between 5and 15% (vol.) in air. When unconfined it is not explosive but it can explode if confined.

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iii) Hydrogen Cyanide and Sodium Cyanide

Hydrogen cyanide (HCN) exists as a gas in this process and is present only as a transient component in the reactor outlet mixture flowing into the absorber, where the majority of it reacts to form sodium cyanide.

Hydrogen cyanide gas is colourless, with a mild odour similar to bitter almonds. Sodium cyanide exists in this plant in solution or as a white solid in brlquettes..

Hydrogen cyanide and sodium cyanide are highly toxic by ingestion, inhalation and skin absorption. The cyanides are true noncumulative protoplasmic poisons (i.e. they can be detoxified readily). They combine with those enzymes at the blood/tissue interfaces which regulate oxygen transfer to the cellular tissues. Unless the cyanide is removed, death results through asphyxia. The warning signs of cyanide poisoning include: dizziness, numbness, headache, rapid pulse, nausea, reddened skin, and blood sh6t eyes. More prolonged exposure causes vomiting and labored breathing, followed by unconsciousness, cessation of breathing, rapid weak heart beat, and death. Severe exposure (by inhalation) can cause immediate unconsciousness; this rapid knockdown power without any irritation or detectable odour to some people makes hydrogen cyanide more dangerous than other materials of comparable toxicity (e.g. hydrogen sulphide).

The IDLH (Immediately Dangerous to Life and Health) concentration of hydrogen cyanide gas is 50 parts per million (ppm) in air, and the TLV (Threshold Limit Value) in Australia is 5 ppm for an 8 hour period. In the USA a revised TLV of 4.7 ppm (down from 10 ppm) has been advised with effect from September 1989. Concentrations of 100 to 200 ppm for exposures of 30-60 minutes can be fatal, and exposure levels of 300 ppm or more are rapidly fatal unless prompt, effective first aid is administered.

Hydrogen cyanide gas is flammable in the range 6 to 41% in air.

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iv) Carbon Monoxide

Carbon monoxide is a colourless, odourless gas of about the same density as air. When inhaled it combines with haemoglobin in the blood, rendering it incapable of carrying oxygen to the tissues, thus producing asphyxia.

Concentrations of 1000 to 1200 ppm over 1 hour can be dangerous. Carbon monoxide is eliminated from the lungs when air free from the gas is inhaled.

As carbon monoxide is present only in the reactor products and absorber overhead gas streams at quite low concentrations, it is unlikely to present a hazard in the event of a leak, either on or off site. Its presence will,

-however, increase the toxic severity of hydrogen cyanide if a mixture is released.

4.3 Review of Safety Record of Similar Facilities

4.3.1 Du Pont Safety Record

Du Pont have consistently been a leader in industrial safety. Their record over many years has shown them to be far ahead of other chemical companies -in their safety and health activities. In 1988 Du Pont's figures showed the company to be 83 times safer than the all industry average, and 23 times safer than the chemical industry average as reported in the NSC USA statistics (Ref. 36). Du Pont employees were 50 times less likely to experience injury on the job than the average US citizen off the job.

This record is the result of a total commitment to safety which is evident throughout the organisation and its facilities. All the essential components of high level safety management (Ref. 37) are well established and maintained by -Du Pont. For. example, Du Pont's Safety and Health Policy and the commitment to this policy is spelt out in clear and strong terms (Refer Appendix D). This policy applies to all Du Pont activities and is implemented vigorously.

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Du Pont's approach emphasises prevention and incorporates risk analysis throughout all phases of project development and operation.

4.3.2 Safety Record of Sodium Cyanide Plants

The accident and injury record at the Memphis Sodium Cyanide Plant was examined. The injury statistics showed the plant to operate with a similar rate of total reportable injuries to that of Du Pont overall. Refer Appendix D.

The majority of incidents are of a minor nature and reflect Du Pont's emphasis on reporting and acting on all safety concerns. Several incidents involved small releases of HCN or sodium cyanide dust. In each case actions were subsequently taken to avoid recurrences.

4.4 Review of Engineering Codes & Standards

The requirements of recognised engineering codes and standards applicable to process design will be observed in the plant design. At this stage of the project final code and standards have not been specified, however in principle Du Pont will adopt relevant Australian and industry standards.

Where Du Pont'spreferred standard exceeds the safety requirement of Australian Standards the higher standard will be adopted subject to the approval of the W.A. authorities.

4.5 Review of Safety Engineering Design

HAZOP Study:

As noted in Section 2.5.1 the EPA requires that a Hazard and Operability (HAZOP) study be carried out by an independent party. The HAZOP study will meet Du Pont's internal standards and the results of the study will be assessed by the W.A. Department of Mines.

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A HAZOP study for such a plant will normally be performed on a set of Piping and Instrumentation Drawings (P & ID's) as they are being finalised and will take several weeks to complete. The HAZOP team includes key plant design and operating personnel, with specialists involved when required. HAZOP technique is

essentially a 'what-if' exercise which focusses on appropriate sub-sections of the plant in order to ensure that the plant can be controlled or fail-safe under all credible circumstances.

A list of Action Items will be generated in the HAZOP study for further analysis, and these may result in changes to plant design or operating instructions after further in-house discussion.

4.6 Domino Effects

There are other potentially hazardous facilities in the adjoining and nearby areas which could affect the risk levels for Site A. The potential for propagation of an accident (the "domino effect")

depends on a number of factors:

The form and energy level of the initiating event and its

- potential effect at the Du Pont facility.

The vulnerability of the Du Pont plant to the potential

effect.

The probability that the plant can be shutdown or otherwise put into a safe condition before any adverse domino effect

can result.

Explosion and fire are the major propagating effects, and these are discussed below. In addition, some effects may arise from a common cause, such as earthquake, storm, failure of electricity or

gas supplies.

1 . Explosion

An explosion could occur within several of the nearby facilities, including Coogee Chemicals, CSBP, AGR, KNC, WMC,

andBP. Also, accidents could arise from transportation

incidents involving pipelines, rail, road and shipping. Damage from explosions results from overpressure, impulse and

missile impact.

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2. FIre

Fire could occur in the facilities noted above, however only fires within 200m are likely to initiate any domino effects. Accordingly only Coogee Chemicals, nearby pipelines, the adjacent roads and rail facilities are close enough to produce such impacts.

There is the remote possibility of a toxic gas cloud or a fireball from facilities further away, such as WMC, the. BP refinery or a ship.

In the risk assessment section the rIsks of the incidents listed above are estimated in order of magnitude terms in order to compare them with risks arising from the Du Pont complex itself.

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5.0 RISK ASSESSMENT

5.1 Methodology

Det norske Veritas' Risk Assessment Methodology is an advanced systematic procedure for quantified risk assessment (QRA) and analysis.

The methodology employs system analysis, current calculation methods, computer models, expert analysis at critical check points, a number of databases and predictive analytical techniques, cumulative risk assessment and presentation of results as individual risk contours, and/or group risk curves.

A module-based computer systemis used for modelling, calculation--------------------- - routines, data storage and risk integration and graphics. Flexibility for individual study requirements is maintained and user knowledge and responsibility is essential. The methodology is clear, logical and coherent and is designed to enhance expert use. As such the Verjtas system is suitable for detailed studies where complete understanding as well as valid results are the objectives.

Figure 5.1 is a flow chart of DnV methodology.

External Data Requiremen (Specific to Study)

- System analysis and description

- Risk objectives

- Risk criteria

Specific failure data

- Specific material data

- Control, protection and emergency response information

- Meteorological data

- Population data

- Maps of locality and layout

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Internal Data Available

- Failure database (components, systems, generic data, human error)

Material database (chemical, flammability, toxicity)

- Hazard levels and risk criteria

Models & Techniques Available

- Fault tree analysis

- Event tree analysis

- Heat flux (pool fire, jet fire, bleve/fireball, flashfire)

- Explosion overpressure (UVCE, blast attenuation)

- Toxic dispersion (Dense gas, neutral and buoyant gas spills on land and water)

- Toxic dose and probit calculations

- Individual risk contours

- FN group risk curves

- Other pre-processing or post-processing models as appropriate e.g. risk distribution and other distribution functions, sensitivity analysis etc.

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FIGURE 5.1 VERITAS QUANTIFIED RISK ANALYSIS METHODOLOGY

SYSTEM ANALYSIS & DESCRIPTION I

HAZARD IDENTIFICATION FAILURE CASE DEFINITION

FAILURE I FREQUENCY I DATABASE I ASSESSMENT I

- 21 COMPONEN '.AVAlLAB

I

DATA

FAULT TREES

CONSEQUENCEI I MATERIAL ASSESSMENT ri DATABASE

CHEMICAL FLAMMABILITY

TOXICITY

SPECIFIC ENERA I SYSTEM CHECK Y ESCRIP

DATA N METEOROLOGICAL

FIRE I DATA

EXPL.

IPOPULI BROAD CHECK TOXIC I TION SYSTEM (DISPERSION) CONTROL DATA

DATA PROTECTION &

EMERGENCY TOP EVENT RESPONSE

IGNITION FREQUENCIES SYSTEM BARRIERS ROCEDURE

ERRORS _ EVENT _ __

CHECK CHEC CHECK TREE

CRITERIA

COMPA- RISON WITH

RITERII

RISK I I END EVENT HAZARD AREA I ISOURCE I MAP

FILE t 1FREQUENCIES DIMENSIONS LOCA- IDIMENSIONIS ________ TIONS

INDIVIDUAL I { RISK ESTIMATION

RISK

CONTOURS CUMULATIVE RISK ASSESMENT

FN GROUP RISK ASSESSMENT k

. RISK CCEPTA Y ES SL

NO

Note: Hazard and Operability studies can also be used for system checks

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5.2 Hazard Identification

5.2.1 Introduction

This study has been developed by postulating a series of "unwanted events' and estimates the likelihood (frequency) and the possible consequences of such events. No detailed analysis is given of the plant malfunctions which could lead to these events (human error, control system failure etc.) as there is a commitment by Du Pont to carry out a HAZOP study on the process design. (Ref. P.E.R.)

In the following sub-sections, credible chemical release events are described qualitatively, and in subsequent sections a quantitative exercise is carried out to produce estimates of risk to the public and adjacent facilities.

Only incidents which are estimated to contribute to off-site risk are included in the quantitative section. For any toxic gas release, downwind dispersion calculations are carried out. If the hazard distances are clearly contained within the site boundary, then the incident may be excluded from further analysis.

For this preliminary risk analysis, it was necessary to make a range of assumptions regarding the design, operation. and management of the proposal. These assumptions are summarised in Appendix K.

Hazardous incidents associated with the proposed plant will involve the release of ammonia, natural gas or hydrogen cyanide gas to the atmosphere from pipework, storage vessels and process equipment to produce toxic or flammable vapours, capable of propagating the event or causing off-site human harm or damage.

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It is essential that proper permit and supervision systems are applied to any excavation or construction work near the pipeline, and this is assumed to be the case in this study for estimations of failure rate.

However the line may be damaged, it is assumed in this study

that any leak will discharge directly to atmosphere, either because: -

- it is open to atmosphere already, or

- the line pressure is high enough to erupt through to the surface.

Assumptions and calculations for ammonia source and release models used in this PRA are summarised in App. F.

5.2.3 Bulk Ammonia Storage

Design details are not yet finalised for this vessel, so it was estimated that a storage vessel of approximately 3 tonnes would be installed to meet the feed requirements of the plant when the main ammonia pipeline supply is not available. it is assumed that the vessel will be installed with standard mechanical and process protection and isolation systems, and two failure cases are used for this analysis:

- catastrophic failure

- disruptive failure

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For this risk analysis gas supply line failures in the section between the metering station and the Du Pont plant are examined, a line length of about 250 metres. The action of the flow limiting valve and the SECWA shut-off valve will limit the initial gas release to the hold-up in this section of line.

Natural gas is supplied by SECWA at about 4500 kPa and is let down to about 1400 kPa outside the plant boundary. Failures in the latter section of the line are considered.

Methane, the major constituent of natural gas, is much lighter than air at ambient temperature but the cloud given by cold methane and air may be denser than air. A full bore rupture of the feed gas pipeline would most likely result in jet dispersion producing a buoyant cloud or plume. For a smaller leak jet dispersion may apply or, if the jet momentum is dissipated, a dense vapour cloud may result from thermodynamic effects (chilling of the vapour/air mix). For failures of the natural gas line both dispersal mechanisms are considered in the calculation of hazard distances for flammable mixtures.

In a momentum jet release damage will be caused by heat radiation, if the jet ignites. Ignition of a dense vapour cloud will cause injury by direct flame contact if a person is within the vapour cloud, therefore distances to the lower flammable limit are estimated for dense cloud releases, whereas heat radiation distances are given for jet releases.

5.2.5 Process Plant Failures

5.2.5.1 Liquid Ammonia Line to Vaporizer

It is assumed that liquid ammonia is pumped to the vaporizer from buffer storage and that either a full bore (guillotine) failure or a disruptive leak occurs, releasing warm, pressurized ammonia to the atmosphere.

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5.2.5.2 Failure of Ammonia Vaporizer

There is insufficient volume in the vapour space of the vaporizer to produce a large release of ammonia, therefore only liquid releases are considered, as foil ows:

Vessel rupture - 1.5 tonnes released rapidly

Disruptive failure - 25mm hole in liquid space

5.2.5.3 Relief Valve Opening on Vaporizer Outlet Line

As this RV will discharge to the flare header, no release of ammonia to atmosphere would result, except in the unlikely event of loss of flame at the flare at the same time.

5.2.5.4 Fracture of Mixed Gas Line to Reactor

Ammonia, methane and air flow to the reactor at about 700C and 70 kPa. Any release from this line may result in danger in the area immediately around the leak, depending on magnitude and direction, but the vapours would behave buoyantly and disperse rapidly to concentrations which were not flammable or toxic beyond the site boundary. In any case, such a release would be detected rapidly and an ESD would limit the time of discharge to a few minutes.

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5.2.5.5 HYDROGEN CYANIDE RELEASES

There are a number of potential releases of hydrogen cyanide (HCN) gas to the atmosphere.

- Via bursting discs on the reactor system. - From failure of the reactor outlet line. - Via an un-ignited flare during start-up. - From failure of the start-up vent line.

Two bursting discs will be installed, one on the reactor itself and the other , on the reactor outlet line to the absorber as ultimate protection for the reactor circuit from damage to equipment through overpresgure. They will discharge to individual vent lines about 25m high in order to disperse the vapour-s safely. If a digc bursts there will be a short duration emission of gas to the atmosphere, containing up to 8% wt. HCN. The system would depressurise almost instantaneously (operating pressure is only about 30 kPa), the air flow would be cut immediately and an ESD of the reactor section would be initiated automatically, cutting HCN production in less than a minute.

At any time there will be about 0.7 kg of HCN in the reactor, WHB and outlet line and no more than 2 kg of HCN in the whole reactor/WHB/absorber system. Production of HCN is about 1 kg/s under normal operating conditions.

These discharges have been modelled using a conventional gas dispersion model for a complete range of weather categories and the results show that ground level concentrations would not exceed 10 ppm (vol) HCN for any of the cases considered.

This dodelling exercise did not take into account the temperatures of the emissions (up to 11000C and 2300C for the reactor and reactor outlet) which would give an added buoyancy to the stack discharge and further reduce downwind concentrations.

These concentrations are low (around the TLV level) and would only just be detectable by smell. No human harm would result from exposure to such low levels, even for long periods, and such emissions would last only a few minutes at the most. As noted elsewhere in the report (e.g. App.A) the level of concern for HCN is a concentration of 50 ppm (IDLH) or more, and at this concentration only exposure times of 30 minutes or more would result in human harm.

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DnV concludes therefore, that discharges from the two bursting disc stacks would not endanger humans, and these events have the highest estimated frequency of all the potential HCN release events. Experience elsewhere indicates that the disc on the reactor outlet/absorber feed line could discharge about once per year on average.

The estimated frequencies for the other HCN release events are much lower, for example failure of the absorber feed lin is estimated to occur at a frequency of around 100 (X 10 events/year) for a 6 m section of line, using appropriate failure rate data for this service. Such a failure could range - from discharge from a flange or broken small bore fitting to a guillotine failure, but the onsequèr1ces would be similar to those described above - rapid depressurising and shut down would limit any discharge to a few minutes and the ground level concentrations beyond the plant boundary would not pose any significant danger. The secondary gas containment system described in Section 3.3.3 is proposed to provide added protection against release to the atmosphere.

HCN releases during start-up could occur either:

- from flame-out of the flare during the period when HCN was being produced (only a small portion of the start-up time) or

- failure of the start-up vent line to flare

Again, the estimated frequencies for these events are low and in any case the consequences are of the same magnitude as those described above - short duration releases resulting in ground level concentrations of HCN which would not endanger humans off-site.

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5.3 Event Frequency

It is necessary to estimate the frequencies of the failure cases mentioned in the previous section so that frequency and consequence values can be combined to give a quantitative assessment of risk from this installation.

Failure rate frequency assessments take into account historical data (where available and relevant), materials research and fracture mechanics, the results of which can be used to assist in fault tree analysis. In addition, site- specific factors such as manning levels, adjacent facilities, etc, are used to modify these

- assessments for a particular study.

In this study pipework/systems reliability and failure data have been used from a range of sources:

OREDA (Offshore Reliability Data) (Ref. 13) Rijnmond Study (Ref. 4) CONCAWE

(Ref. 33) Lees

(Ref. 1) WASH 1400 (Ref. 31) WOAD

(Ref. 32) DnV Australia FAILURE DATA BASE

Failure rates used for process items are given in Table 5.3. These rates are in line with those used for the Kwinana Cumulative

Risk Analysis (Ref. 23) so that hazardous events from this study can easily be integrated into the cumulative analysis at the next update.

For process plant incidents which require simultaneous failures or a series of events arising from some initiating event it is normal to construct fault or event trees in order to estimate frequencies of a range of outcomes. As this project is in an early stage of development, details of instrumentation and safety are not available, therefore incident frequencies are based on DnV experience from similar risk analysis studies.

44

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TABLE 5.5: COMPONENT FAILURE RATES USED IN PRA

------------------- ----------------------------------------------

Failure Case Failure Frequency (events/year)

7 ------------------------------------

Pressure vessels: Catastrophic Major leak

- - Process_pipes_ -- -- >300mm dia. 200 150 100 50 25

Cross-country pipes: Guillotine Major leak

6.5 x 10_6 1.0 x 10

- 1.6 x 1 0 /1 Om - -- 2.4 x 10 5/lOm 3.2 x 10 5/1 0m 4.7 x 10'5/1 0m 9.4 x 10 5/1 0rn 1.9 x 10 4/1 0m

1.0 x 10 8/1 0m 3.0 x 10 8/1 0m

Pumps: Rupture 10 x o_6 Major leak

100 x iø_6

Valves: Rupture 1.0 x 10 9/hr Major leak 1.0 x 10 8/hr

-----------------------------------------------------------------

DIJPONTRA . RPT 17/7/1 989

¼ OV3J(f

S

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TABLE 5.4: SUMMARY OF HAZARDOUS INCIDENTS GENERATED FOR PRA

Unit/Vessel/Pipe

----------------------------------------------------------------------------Incident Release Duration Freqency

-------------------------------------------------------------------------------- kg/s(te) Mlii. 10 /yr

Ammonia Release Cases

Ammonia pipeline Guillotine Ste 5 2.5 Major leak 1.25 5 7.5

Buffer storage vessel Rupture 2te 2 6.0 Major leak 9 5 60.0

Vaporizer feed Guillotine 1 2 125.0 Major leak 0.2 5 1125.0

Vaporizer Rupture ite 2 6.-0 Liquid leak 9 4 300.0

Hydrogen Cyanide Release Cases

Reactor Bursting disc 1 <1 10 106 Reactor outlet line Bursting disc 1 <1

Reactor outlet line Guillotine 1 <2 10 Major leak 0.25 5 70

Start-up gases Flare flame-out 1 5 100 Vent line leak 1 5 150

Natural Gas Release Cases

1400 kPa supply Guillotine 1 .4te 2 0.3 Major leak 5 0.9

Miscellaneous

Reactor feed line Major leak 11 5 103

Flare header Major leak 1 5 10 10 4 HCN from warehouse incident

--------------------------------------------------------------------------------

Contaminated NaCN

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47

5.4 Consequence of Failure

Table 5.4 is a summary of the hazardous incidents described in Section 5.2, with estimated frequencies calculated using the data and methods presented in Section 5.3.

Release rates were calculated by standard methods, described in Appendix I and the duration times are estimated from vessel inventory, flow rates or expected intervention/shut_off times.

In the quantified risk analysis, predicted toxic gas concentrations are combined with time estimates for cloud/plume travel to give dosage figures and the distances for human harm arising from each incident.

The relationship between toxicity in terms of percentage fatality, concentration and time of exposure is shown in the following "Ammonia Toxicity" figures. Curves for 10,000 ppm, 5,000 ppm and 1,700 ppm are shown based on probit equations (1) as developed by Withers et al. (Refs. 26,27,28) and (2) as used by DnV in this and previous studies.

The curve for a "vulnerable" population, representing particularly sensitive persons is also shown for each level. While there is some uncertainty at the upper and lower ends of the probit curves due to lack of data at these levels, simple extrapolation of the curves within recommended limits indicates that risk of fatality to the public does not arise for short exposures (less than half an hour or so) at or below the 1,700 ppm level.

It is generally accepted that gas cloud modelling and the casualty predictions give conservative results (i.e. over-estimates of injury) when the actual consequences of recorded accidents are compared with those predicted. This is because of the idealized assumptions in the models versus the realities of landscape, barriers, human reactions, weather patterns, and so forth.

However, there has to be some basis for safety assessment and emergency planning, therefore this approach is adopted of using reasonably valid models to give (probably) conservative values for planning purposes.

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lot

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48

5.5 Risk of Domino Effects

Possible domino effects described in Section 4.6 have been reviewed and the probabilities of external accidents affecti.ng the Du Pont plant have been assessed in order of magnitude terms. The more 'credible incidents are discussed below:

FIre/Explosion at Coogee Chemicals

It is possible that a fire could occur in the tank farm, most likely a pool fire, at a frequency of the order of 10 x 10 6 events/year, however any such fire would be confined to the tank farm area. As the separation distance between the tanks and the Du Pont plant is more than lOOm, radiation effects from a fire would not cause any damage to the -process equipment, although the storage and rail loading facilities could be damaged.

Within the storage and loading facilities, sodium cyanide is contained within shipping containers or other robust packaging systems designed to withstand - most situations. Provided that Du Pont emergency procedures are followed no release of product should be expected to result from fire or other emergency in adjacent facilities.

Pipeline Leak

Five pipelines run parallel to the existing railway track and supply the following products to the nickel refinery:

- liquid ammonia - hydrogen - syn. gas - nitrogen - carbon dioxide

Only the first 3 chemicals are hazardous if released to the atmosphere. The pipeline corridor is about 65m from the nearest process equipment and at this distance. The risk of a pipeline failure resulting in damage to the plant sufficient to cause domino effects is assessed to be low compared with other risk levels for the installation. There are some concerns however, about the proximity of the railway line to the pipe track and these are discussed below.

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Railway Accident

Existing rail traffic is light, about 2 shipments of nickel ore per week, and this product would not present a hazard to the Du Pont plant if a derailment and spillage occurred. Rail traffic will increase when Du Pont commences rail loading and DnV believes that a serious derailment, with the potential for damaging the pipelines, is a credible' event. Although, as noted in 2 above, such an incident would not necessarily create a domino effect, some recommendations are made in this report (Section 6) about protection and rationalization of pipeline routes.

Road Accidents

There is a small probability that a serious accident involving toxic or flammable chemicals could occur on the roads bordering the Du Pont plant site, however, at distances of 200m or more from the process equipment, the chances of escalation are estimated to be too low to warrant preventive action.

5.6 Individual Risk Levels

The risk of individual risk of fatality has been calculated for the facility. The risk is presented as contours representing the risk frequencies of:-

- ten in a million per year (10 x - - one in a million per year ( 1 x 10 ),

- one in ten million per year (.1 x 10_6)

These are shown on Figure 5.2. The criteria level of acceptability for residential areas is 1 x 10 6 which is confined to within 180m of the site boundary except for the eastern side where the contour is contained within the site.

The risk at residential areas therefore does not approach the

criteria level.

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Kwinana Nitrogen Company plant

Chior-alkali CSBP Kwinana plant

works

AGR sodium cyanide plant

TV IV1

nickel refinery

Office Road

Legend Contours x 10-6 per year

Note Contours show individual risk of fatality per million per year.

0 1 2km

Scale

Figure 5.2

INDIVIDUAL RISK CONTOURS

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5.7 Cumulative Risks

The Du Pont facility risk levels decrease to below 10 per year in the immediate vicinity of the plant. This effect zone is between the Kwinana Cumulative Risk Study contours 10 to 10, that is, above 10 but not exceeding 10.

Adding the Du Pont levels to the existing cumulative risk levels will result in a small zone above 10 at the plant site. This is no higher than other existing or proposed chemical plants in cumulative risk study.

-- Determination ofnew levels inthe immediate vicinity of the plant - - requires reference to the precise cumulative risk levels at each location, which are not available to DnV. However, from examination of the cumulative risk contours, it is not likely that the plant off-site risk levels will result in changes to the cumulative risk contours. The DnV failure case information will be included in the next update of the cumulative risk study.

The Du Pont risk levels, even well below the EPA criteria levels, do not impact on residential areas. Accordingly the conclusion of the Cumulative Risk Study of the Kwinana Industrial Area (Ref. 23) that the risk to the nearst residential area is in fact below the one in a million (10 ) per year level, which is considered by the EPA to be negligible, should not be affected.

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6.0 CONCLUSIONS

6.1 Off-Site Risks

Individual risk from the proposed plant is significantly below 1 x 10 per person per year in the nearest residential and public access areas and the assessed risk levels therefore satisfy the EPA guidelines on risk acceptance.

6.2 In-Plant Risks

Risks within the plant boundary arise mainly from the storage and handling of ammonia and the presence of hydrogen cyanide (HCN) as a transient product in the process. Established, stringent engineer iig - and operatfng procedures will be used by Du Pont personnel to minimise the possibility of in-plant exposure to these chemicals.

6.3 Domino Effects

A number of hazardous facilities in the adjoining and nearby areas have been examined in order to assess their potential for propagation of an accident (the "domino effect"). Separation distances between any credible incident and vulnerable sections of the sodium cyanide plant are great enough to ensure that the risks of domino effects are low compared with other risk levels for the installation.

6.4 Cumulative Risks

The Du Pont facility risk levels decrease to below 1077 (per person per year) in the immediate vicinity of the plant. This effect zone is between the Kwinana Cumulative Risk Study contours 10 to 10, that is, above 10 but not exceeding 10.

Adding the Du Pont levels to the existing cumulative risk levels will result in a small zone above 10 at the plant site. This is no higher than other existing or proposed chemical plants in the cumulative risk study. Risk levels at residential areas should not be affected.

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6.5 Pipeline Recommendations

A liquid ammonia pipeline will be installed to supply the proposed plant. An existing five-pipeline corridor leading to the nearby nickel refinery runs parallel to the railway track to the west of the Du Pont plant. Although the risks from these pipelines to the sodium cyanide plant are assessed to be low, DnV recommends that the total pipeline network in this area be examined critically with a view to rationalizing pipeline routes and improving surface marking and protection where necessary.

6.6 Transport

Risks arising from transport of sodium cyanide were not assessed in detail in this report, however the use of established double layer- packaging techniques and transportation of the packed chemical within shipping containers will minimise the occurrence of cyanide spillage from an accident.

6.7 Abnormal Emissions

Events resulting in minor emissions e.g. during process upset or flare flame out during start up have been considered in this study and found to have, at worst, short term effects at non-harmful levels beyond the plant boundaries.

To provide for planning and control measures, including licensing if considered appropriate, it is recommended that Du Pont provides to the Pollution Control Division of the Department of Conservation and Environment further information as it becomes available on possible emissions and the control and monitoring systems proposed.

6.8 Emergency Procedures

Du Pont will prepare emergency procedures for the proposed plant, basing them on established practices at their other sodium cyanide manufacturing facilities. The company will also co-ordinate their emergency procedures with the Kwinana Integrated Emergency Management Scheme (KIEMS) which is currently being drawn up.

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6.9 Safety Record

From examination of Du Pont Health and Safety Records and their systems for maintaining process safety, DnV concludes that Du Pont has a total commitment to safety which is evident throughout the organization and its facilities, and that they are industry leaders in this respect.

6.10 Management of Safety, Occupational Health, Reliability and Environmental Protection

Du Pont Australia will be employing safety systems developed by the Du Pont Organisation in its extensive manufacturing activities and applied to meet the requirements - of the West Australian Authoritje. From the commitment given to safety by Du Pont in all of its activities, and its outstanding safety record, it is expected that this plant will be operated with a very high level of both in-plant and public safety.

6.11 Hazop & Other Future Safety Studies

Du Pont is committed to carrying out a Hazard and Operability Study during the detailed design phase and will ensure that action items arising from this study are implemented.

The assumptions and results of this Preliminary Risk Analysis will be reviewed when the plant design is finalised to check that the results and conclusions remain valid.

Other studies will be carried out to examine critically fire safety, emergency preparedness and commissioning procedures, and in-service safety will include regular audits.

These studies will be carried out to meet Du Pont's internal safety requirements as well as those of the W.A. Department of Mines.

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6.12 Training, Commissioning & Start-Up Procedures

Preparation for the safe start-up of the plant will include the involvement of experienced personnel throughout the building, testing, commissioning and start-up phases of the project.

Experienced personnel will be used in operating the plant until thorough training of new personnel is completed. Training will

include plant and process familiarization, safety induction and training, operating procedures and emergency response.

Start-up and operating procedures generally will be considered in the HAZOP and detailed procedures will be reviewed prior to start- up.

6.13 Natural Disasters

The proposed plant is located in seismic zone A, as defined in the SAA Earthquake Code (AS 2121) and will be subjected to a low risk of exposure to a damaging earthquake. Buildings and plant will therefore be designed in accordance with AS 2121

The installation will be built to withstand any extremes of weather expected in this region and no other natural disasters are envisaged. -

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7.0 REFERENCES

1. F.P. Lees (1980). Loss Prevention in the Process Industries, Vols 2 and 2.

2. Canadian Environmental Protection Services: T.I.P.S. Handbooks.

Introduction Manual (1985) Ammonia (1984)

3. N. Irving Sax (1979). Dangerous Properties of Industrial Materials.

4. Report to Rijnmond Public Authority (1982). Risk Analysis (...) in Rijnmond Area.

5. U.K. Health and Safety Executive. Canvey Investigation Report (1978), Canvey Second Report (1981).

6. Chemical Industries Association Code of Practice: large scale storage of fully refrigerated anhydrous ammonia (U.K.).

7. A.I.C.E. Loss Prevention Manuals (1984): (Various authors)

(1983) Survey of refrigerated ammonia in the U.S. and Canada.

Accidental releases of ammonia: An analysis of reported incidents.

8. J.J. Closner and R.O. Parker, 0 and G Journal, March (1977). Safety of Storage Designs Compared.

9. The Kwinana Air Modelling Study Department of Conservation and Environment Perth, Western Australia, December (1982).

10. Correspondence dated 24th February (1987) Hope Valley Base Station annual wind speed data, Pollution Control Division and Environmental Protection Authority.

11 . Notes on Meteorological Statistics Representative of the Kwinana Region from Pollution Control Division, Department of Conservation and Environment.

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SRS data bank, UKAEA (UK).

OREDA: Det norske Veritas - Offshore Reliability Data

The Warren Centre (1986). Major Industrial Hazards Project Report. University of Sydney.

Heavy Gas Dispersion Trials at Thorney Island. Symposium (1984). Journal of Hazardous Materials Vol. 11, June (1985).

S.F. Jagger, (1983). Development of CRUNCH Dispersion model. U.K. Atomic Energy Authority.

L.S. Fryer & G.D. Kaiser, (1979). DENZ - Computer Program for the calculation of the dispersion of dense toxic or explosive gases in the atmosphere. U.K. Atomic Energy Authority.

U.K. Health and Safety Commission. Advisory Committee on Major Hazards. Third Report: The Control of Major Hazards, (1984). H.M.S.O.

R.J. Bettis, G.M. Markhviladze and P.F. Nolan (1987). Expansion and evolution of heavy gas and particulate clouds. Journal of Hazardous Materials Vol. 14 No. 2.

Roberts and Handman. Minimize Ammonia Releases. Hydrocarbon Processing, March, (1986).

TNO, The Hague. Analysis of the LPG Incident San Juan Ixhuatepec, Mexico City, 19th November (1984).

J.I. Petts, R.M.J. Withers and F.P. Lees: The Assessment of Major Hazards: The Density and other characteristics of the Exposed Population around a Hazard Source. Journal of Hazardous Materials Vol. 14 No. 3, March 1987.

Kwinana Cumulative Risk Analysis (Technica Report No. C715, March 1987 and Revision C1628, November 1988).

EPA Bulletin 309, November 1987.

AS 2022 - 1983 Anhydrous Ammonia Code.

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F. Pedersen and R.S. Selig: Predicting the consequences of short-term exposure to high concentrations of gaseous ammonia, Journal of Hazardous Materials, Vol. 21, No.2, March 1989.

J. Withers et al. The Lethal Toxicity of Ammonia. A Report to the Major Hazards Advisory Panel. I Chem.E (UK)

Ammonia Toxicity Monograph - The Institution of Chemical Engineers - 1988

Kwinana Beach : Wells Park Structure & Landscape Plan October 1988 - Kwinana Industries Co-ordinating Committee.

EPA Bulletin - 278.

Wash 1400.

World Offshore Data Bank.

CONCAWE (European Oil and Gas Pipeline Study).

Risk assessment for installations where liquefied petroleum gas (LPG) is stored in bulk vessels above ground. - G.A. Clay, R.D. Fitzpatrick, N.W. Hurst (Sheffield, U.K.), D.A. Carter and P.J. Crossthwaite (Bootle, U.K.).

Site Selection Study, Sedwin Cyanide Manufacturing Plant. Kinhill Engineers., May 1989.

Accident Facts 1988 edition: National Safety Council. Chicago U.S.A.

M.O.R.T. - The Management Oversight and Risk Tree. (Johnson, ERDA, DnV, various references).

Process Flow and Material Balance information for the project: Du Pont June 1989 Drawings No. W 1027245, W 1057056, W 1063088, W 1069749, W 1069750, W 1069751.

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I IL1I LIV I

OF

PROCESS MATERIALS

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APPENDIX A.

AMMONIA:

Physical Properties:

At ordinary temperatures and atmospheric pressure anhydrous ammonia is a pungent colourless gas. - It can be liquefied by a moderate increase in pressure or by lowering its temperature to minus 330C.

Ammonia can readily be detected in the atmosphere by smell, at concentrations as low as 20 ppm v/v. It is extremely soluble in water and some organic solvents, heat being liberated during solution. The main physical constants are as follows:

Atmospheric Boiling Point -33.3°C Freezing Point -77.70C Critical Temperatures 132.40C Critical Pressure - 11420 kPa Latent Heat (1 atm, minus 33°C) 1370.7 kJ/kg.

Liquid Density

682.8 kg/rn3 Vapour Pressure 888 kPa (21 0C) Vapour Density 0.707 kg/rn3 (25°C) Flammable Limits (% by volume in air) 16 - 25% Auto Ignition Temperature 651°C

Ammonia (NH3) is stable at ordinary temperatures but decomposes to hydrogen and nitrogen at elevated temperature.

Ammonia is a fairly reactive gas; it reacts readily with a large variety of substances. High temperature oxidation to form nitrogen and water is one of the more important reactions. This reaction can be effected by many metal oxides, for example copper oxide. Chlorine reacts with ammonia to give nitrogen and ammonia chloride.

Other reactions of possible significance are:

- ammonia plus phcsphorus vapour at red heat (possible fire conditions) to give nitrogen and phosphine;

-

sulphur vapour and ammonia to give ammonium sulphide and nitrogen;

-

sulphur with anhydrous liquid ammonia to give hydrogen sulphide

- tetranitrogen tetrasulphide and ammonia and carbon at red heat to give ammonium cyanide. -

The compounds mentioned are either poisonous, unstable-, can react with air to produce other noxious materials, or are all of the aforementioned.

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TABLE Al: HEALTH HAZARDS OF AMMONIA

Vapour Concentration General Effect Exposure Period ppm Vol/Vol

*25 Odour, detectable by most Maximum for 8 hour persons. working period.

100 No adverse effect for Deliberate exposure average worker, for long periods not

permitted.

400 Immediate nose and throat No serious effect irritation, after 1/2-1 hour.

700 Immediate eye Irritation No serious effect after 1/2 - 1 hour.

1,500 Convulsive coughing, Could be fatal to severe eye, nose and some people after throat irritation. 1/2 hour.

2,000 - 5,000 Convulsive coughing, Could be fatal after severe eye, nose and 1/4 hour, although no throat irritation, recorded fatalities

below 5,000 ppm.

5,000 - 10,000 Respiratory spasms. Could be fatal Rapid asphyxia. withIn minutes

11,500 LC 50,30 Lethal concentration to 50%

of healthy population exposed for 30 minutes.

05KE.

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* This is the present Threshold Limit Value (TLV) 1 ppm = 0.72 mg/rn3

For the PRA, probit equations for Average (Healthy) and vulnerable populations were used in assessing probability of fatality. The following toxic concentrations were used as levels of interest in dispersion calculations:

10,000 ppm - LC50

- 1,700 ppm - LClo, emergency level

500 ppm - IDLH,irritant effects

(See Glossary for definitions)

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HYDROGEN CYANIDE & SODIUM CYANIDE

Hydrogen cyanide (HCN) is one of the most deadly poisons known. It is especially dangerous because of its "knockdown" power, i.e., a victim can become unconscious immediately from exposure to a very small amount of HCN and will, therefore, be unable to escape from contaminated surroundings. A smallamount will rapidly cause death. For example, 0.002 ounces (60mg) could be inhaled in ten deep breaths of air containing 3,000 ppm HCN and would kill the average adult. However, 300 ppm HCN in air is considered to be a lethal quantity.

HCN is a true protoplasmic poison. It has somewhat the same effect on the blood as carbon monoxide (CO). The oxygen of the arterial blood is tied-up, preventing it from being absorbed by the tissues of the body. As in the case of CO, the body tends to throw off HCN. If death can be prevented, recovery is normally rapid and complete with no permanent damage occurring. There is no accumulative effect from exposure to HCN.

HCN is taken into the bloodstream by two processes; breathing and absorption through the skin. Poisoning by skin is much slower than by breathing but the effects are identical. In either case, the concentrations that a person can take will vary for different people. To provide a relative measure of the danger of HCN to the average individual, tables (A2, A3) of concentrations and effects are given overleaf.

Sodium cyanide is manufactured as a granular material and formed into briquettes for shipping. As long as it is kept dry it remains stable. If the material becomes damp it will have an ammonia and/or HCN odour. Moisture will cause slow decomposition, releasing HCN (hydrogen cyanide) and ammonia gas. Large amounts of highly toxic, flammable HCN gas will be evolved from contact with acids. Water or weak alkaline solutions can produce dangerous amounts of HCN in confined areas.

Somesafety precautions are to avoid contact with skin or clothing and not to breathe dust.

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HYDROGEN CYANIDE

Physical Properties:

Name

Formula

Health Hazard

Odour

Apprearance

Boiling point

Freezing Point

Specific Gravity, Liquid

Specific Gravity, Gas

Explosive limits

Flash Point

Autoignition Temperature

Solubility

Reaction Hazard

Hydrogen Cyanide, Hydrocyanic acid, Prussic Acid

HCN

Deadly poison by breathing or skin contact.

Mild, somewhat like bitter almonds or peach seek kernels

Colourless - liquid or gas

260C (790F) at atmospheric pressure

-130C (90F)

0.697 (water 1)

0.969 (air = 1)

6 - 41 % by volume

-170C (0°F) (closed cup)

5380C (10000F)

Miscible in all proportions in water

Polymerizes violently in the presence of a base; i.e. NaOH, NH3.

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SODIUM CYANIDE

Physical Properties:

Name Sodium Cyanide

Synonyms Cyanide of Sodium, Prussiate of soda

Formula HaCN

Health Hazard May be fatal if inhaled, swallowed, or absorbed through skin.

Odour None, (but can have slight ammonia and/or HCN odour if damp)

Colour White

Form Solid

Apprearance Granular or Briquettes

Boiling Point 760 mm Hg 14960C (2725°F)

Melting Point 5640C (10470F)

Specific Gravity 1.6

Solubility in H 2 0 37% at 200C (680C)

pH Information 11.3 to 11.7 (Typical for 5 to 25% solutions with no pH adjustments)

Flash Point Will not burn

Instability Very stable when dry

Reaction Hazard - Reacts violently with strong oxidizing agents

8

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Sodium cyanide is manufactured as a granular material and formed into briquet-tes for shipping. As long as it is kept dry it remains stable. If thematerial becomes damp it will have an ammonia and/or HCN odour. Moisture will cause slow decomposition, releasing HCN (hydrogen cyanide) and ammonia gas. Large amounts of highly toxic, flammable HCN gas will be evolved from contact with acids. Water or weak alkaline solutions can produce dangerous amounts of HCN in confined areas.

Some safety precautions are to avoid contact with skin or clothing and not to breathe dust.

1

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TABLE A2: EXPOSURE LIMITS --------------------------------------------------------------------------------

FOR HYDROGEN CYANIDE

Exposure Concentration Description Limit (ppm)

IDLHa 50 The concentration defined as posing an immediate danger to life and health (i.e., causes toxic effects for a 30 minute exposure). -

PEL 10 A time-weighted 8-hour exposure, to this concentration, as set by the Occupational Safety and Health Administration (OSHA), should result in no adverse effects for the

- average worker.

LCLO 178 This concentration is the lowest published lethal concentration for a human over a 10

--------------------------------------------------------------------------------- minute exposure.

a Note that although the focus of these tables are on hydrogen cyanide, sodium cyanide solution can be lethal by ingestion or absorption.

TABLE A3: PREDICTED HUMAN HEALTH EFFECTS OF EXPOSURE TO VARIOUS

---------------------------------------------------------------------------------CONCENTRATIONS OF HYDROGEN CYANIDE.

ppm - Predicted Effect

2 - 5 Odour threshold

20 Causes slight symptoms including headache and dizziness after several hours.

50 Causes disturbances within an hour.

100 Dangerous for exposures of 30 - 60 minutes.

300 Rapidly fatal unless prompt, effective first aid is administered.

S

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METHANE:

Physical Properties:

Molecular Weight Boiling Point Freezing Point (at 101.3 kPa) Density Liquid (-1600C) Vapour Specific Gravity Flammable Limits (in air) TLV

16.04 -161 .5°C -182.5°C 442 kg/rn3 0.55 5.0% - 15.0% Not pertinent*

* methane is an asphyxiant and the limiting factor is available oxygen.

Reference: Chemical Hazard Response Information System - U.S. Coast Guard.

HYDROGEN:

Physical Properties:

Molecular Weight (H2) Boiling Point (at 101.3 kPa) Freezing Point Density (at -253°C) Vapour Specific Gravity Flammable Limits in Air TLV

2.0 -253°C -25 9°C 71 kg/m3 0.067 4.0% - 75% Gas is non-poisonous but can act as a simple asphyxiant.

Reference: Chemical Hazard Response Information System - U.S. Coast Guard.

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CARBON MONOXIDE:

Physical Properties:

Molecular Weight Boiling Point (at 101.3 kPa) Freezing Point Density at -191 .5°C Vapour Specific Gravity Flammable Limits in Air -- TLV - -

28.0 -191 .5°C -199°C 791 kg/rn3 Data not available 12%- 75% .-- -. 50 ppm

Reference: Chemical Hazard Response Information System - U.S. Coast Guard.

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APPENDIX B

ASSUMPTIONS MADE IN

PRELIMINARY RISK ANALYSIS

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ASSUMPTIONS MADE IN PRELIMINARY RISK ANALYSIS

Listed below are the primary assumptions made for this safety study and for the background work leading to this study. They are based on information received from Du Pont on the design and anticipated operation of the sodium cyanide plant, plus DnV's experience in engineering and risk analysis work.

Some design details may differ when the plant is completed and commissioned, but it is not expected that any major changes will occur which lead to greater risks than those estimated in this report, as the assumptions and risk calculation procedures are conservative.

Assumptions Reference

Good operation and maintenance practices DnV will be observed in plant operations.

Liquid ammonia will be supplied by pipeline from bulk storage at CSBP/KNC at a rate of 89 t/d Du Pont (or 1 kg/s) to an intermediate storage vessel at DuPont of 2 hrs hold-up capacity (7.4 tonnes).

The ammonia pipeline is approximately 2,000 m long and is a 50 mm dia. line supplying Du Pont only. DnV Hold-up is about 2.4 tonnes of liquid ammonia.

SDVs at each end of the pipeline will close in 15 to 30 seconds when an ESD of the ammonia DnV pipeline is initiated. Piping arrange ments will prevent backflow of ammonia from the buffer vessel in the event of a line leak.

Adequate protection from vehicle damage to the DnV the ammonia and natural gas pipelines will be installed and proper permit procedures and supervision systems will be applied for any

- excavation or construction work near the pipelines.

Liquid ammonia is pressurised from buffer storage to Du Pont the vaporizer at an average of 89 t/d or 1 kg/s.

Hold-up of liquid ammonia in the vaporizer is Du Pont approximately 2 tonnes.

Relief valves from the ammonia storage vessel and the vaporizer discharge to an (elevated) safe location.

Piping arrangements will prevent backflow of ammonia from the buffer storage vessel in the event of a line leak.

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Relief valves from the ammonia storage vessel and vaporizer discharge to an elevated safe location. Du Pont

The line from the reactor/WHB, in which HCN gas is present at approximately 8% wt, will be DuPont approximately 6 m long and 400 mm i.d., a hold-up of less than 0.1kg of HCN. About 0.7 kg of HCN will be held-up in the reactor/WHB and about 1.2 kg in the absorber during normal operation.

An adequate number of trained personnel will be present to deal with normal operations and these DuPont! people will be trained in the handling of ammonia DnV and emergency response to operational mishaps and possible releases of ammonia.

This risk analysis assumes that site A in the site DnV selection study will be used.

Operating safety features and the checklist DuPont procedures will be as described in Section 4.5 of this report.

The absorption column is assumed to have a reliable caustic/NaCN solution supply system and to be of high reliability. Likewise, the integral flare stack will be fitted with a flame sensor and a- reliable Du Pont pilot gas and ignition system. Fault tree analysis should be used to confirm this, with particular attention paid to common cause failures (e.g. utility failures).

The fire detection and firewater systems will be of high standard and should prevent escalation of most Du Pont on-site fires.

The HCN leak detection system will achieve the Du Pont assumed response tim-es for isolation.

18..,. Adequate alarm and trip systems will be installed to minimise the effects from credible hazardous process Du Pont incidents. These will be checked comprehensively in a HAZOP study.

19. Alarms and trips will be tested on a regular basis. Du Pont

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APPENDIX C

METEOROLOGICAL DATA

LI)

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METEOROLOGICAL DATA

Atmospheric stability, wind speed and wind directions are taken from the Department of Conservation and Environment (DCE) data collected from the Hope Valley Meteorological Station during the year 1980.

The data provides weather occurrences averaged over one year in the six pasquil stability groups A, B, C, D, E and F, for sixteen wind directions and ten wind speed ranges.

This data is input directly to the DnV Risk Assessment Program Met Files. After analysis of gas dispersion model results, three representative weather cases were selected B3, D4 and F2. The data was selected from the files for appropriate grouping to the three representative cases as shown in the following tables.

The sixteen wind directions are maintained with the directional values for each grouping used for all locations within each of the sixteen sectors without modification.

S

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TABLE 1: APPENDIX C

DCE MET DATA - STABILITY CLASS A USED FOR 33 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[3-4.5] 0.2 0.5 0.5 0.8 0.6 0.4 0.2 0.7 0.0 0.4 0.2 1.1 4.6 1.5 0.9 0.2 12.8 [1.5-3] 3.2 6.5 6.1 4.0 2.4 4.8 3.7 3.2 4.2 3.6 3.1 2.7 7.2 5.9 3.0 1.7 65.3

TOTALS 1.5-4.51 3.4 7.0 6.6 4.8 3.0 5.2 3.9 3.9 4.2 4.0 3.3 3.811.8 7.4 3.9 1.9 78.1

PROB .04 .09 .08 .06 .04 .07 .05 .05 .05 .05 .04 .05 .15 .09 .05 .02 1.00

DATA FILED IN A3KWIMET.DAT

DCE MET DATA - STABILITY CLASS B USED FOR B3 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[3-4.5] 1.0 2.3 1.4 3.7 6.5 5.2 2.6 1.9 2.0 1.5 3.4 4.9 9.3 3.5 1.7 0.8 51.7 [1.5-3] 1.9 2.1 3.0 1.3 2.52.4 2.6 1.4 2.2 1.4 1.5 2.5 4.1 2.8 1.1 0.7 33.5

TOTALS

1.5-4.51 2.9 4.4 4.4 5.0 9.0 7.6 5.2 3.3 4.2 2.9 4.9 7.413.4 6.3 2.8 1.5 85.2

PROB .03 .05 .05 .06 .11 .09 .06 .04 .05 .03 .06 .09 .16 .07 .03 .02 1.00 (1.5-4.5] DATA FILED IN 83KWIMET.DAT

DCE MET DATA - STABILITY CLASS C USED FOR D4 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[6-7.5] 0.1 0.2 0.2 0.7 0.6 0.2 0.1 0.1 0.9 5.810.8 1.0 0.5 0.6 0.4 0.4 22.6 ) [4.5-6) 0.6 1.2 0.8 1.8 3.1 1.7 1.1 1.1 1.2 3.9 9.3 3.5 1.9 1.1 1.0 0.8 34.1

[3-4.5] 1.1 1.6 0.9 1.6 2.8 2.3 2.3 2.0 1.8 1.4 3.2 1.3 1.4 0.4 0.8 0.7 25.6

TOTALS - [4.5-6] 1.7 2.8 1.7 3.4 5.9 4.0 3.4 3.1 3.0 5.312.5 4.8 3.3 1.5 1.8 1.5 59.7 [3-7.5] 1.8 3.0 1.9 4.1 6.5 4.2 3.5 3.2 3.911.123.3 5.8 3.8 2.1 2.2 1.9 82.3

PROB .02 .04 .02 .05 .08 .05 .04 .04 .05 .13 .28 .07 .05 .03 .03 .02 1.00 [3-7.5] DATA FILED IN C4KWIMET.DAT

DCE MET DATA - STABILITY CLASS D USED FOR 04 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[6-7.5] 0.6 1.0 0.9 1.1 1.2 0.4 0.1 0.1 1.7 4.8 2.7 3.7 2.7 1.9 0.8 0.6 24.4 [4.5-6] 1.2 1.3 0.8 1.4 2.9 1.4 0.7 1.2 3.2 4.4 2.7 2.4 2.5 1.6 0.7 0.8 29.1 (3-4.5] 0.9 1-.9 0.8 0.8 2.2 1.9 0.8 2.0 2.6 2.4 1.3 0.8 1.3 0.7 0.3 0.4 20.9 (1.5-3] 0.2 0.5 0.4 0.4 0.6 0.6 0.5 0.6 0.4 0.3 0.3 0.3 0.3 0.1 0.1 0.2 5.9

TOTALS [4.5-6] 2.1 3.2 1.6 2.2 5.1 3.3 1.5 3.2 5.8 6.8 4.0 3.2 3.8 2.3 1.0 1.2 50.0 [3-7.5] 2.9 4.7 2.9 3.7 6.9 4.3 2.1 3.9 7.911.9 7.0 7.2 6.8 4.3 1.9 2.0 80.3

PROB .04 .06 .04 .05 .09 .05 .03 .05 .10 .15 .09 .09 .08 .05 .02 .02 1.00 [3-7.5] DATA FILED IN D4KWIMET.DAT

S.

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TABLE 2: APPENDIX C

OCE MET DATA - STABILITY CLASS E USED FOR 04 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[4.5-6] 0.0 0.2 0.4 0.5 0.10.1 0.0 0.0 0.2 0.2 0.1 0.2 0.1 0.1 0.0 0.0 2.2

PROB .00 .09 .18 .23 .05 .05 .00 .00 .09 .09 .05 .09 .05 .05 .00 .00 1.00

DATA FILED IN E4KWIMET.DAT

DCE MET DATA - STABILITY CLASS E USED FOR F2 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[3-4.5] 0.6 3.0 3.6 3.8 3.0 5.0 4.2 8.110.9 3.1 0.7 1.1 1.5 0.6 0.4 0.3 49.9 [1.5-3] 0.7 2.4 4.0 3.1 3.0 4.7 6.6 7.5 6.6 2.7 0.9 1.1 1.5 0.6 0.3 0.4 46.1 [.5-1.5) 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.1 1.6

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

TOTALS

.5-31 0.8 2.5 4.1 3.2 .3.1 4.8 6.8 7.6 6.7 2.8 1.0 1.2 '1.6 0.6 0.4 0.5 47.7 [.5-4.5-] 1.4 5.5 7.7 7.0 6.1 9.811.015.717.6 5.9 1.7 2.3 3.1 1.2 0.8 0.8 97.6

PROB .02 .05 .09 .07 .06 .10 .14 .16 .14 .06 .02 .03 .03 .01 .01 .01 1.00 [0.5-3) DATA FILED IN E2KWIMET.DAT

DCE MET DATA - STABILITY CLASS F USED FOR P2 GROUP

Vel m/s N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

[3-4.5] 0.0 0.7 1.7 1.6 0.6 2.1 1.5 0.7 0.4 0.1 0.0 0.0 0.0 0.0 0.0 0.0 9.4

(1.5-3] 1.5 3.412.812.011.110.2 8.8 4.9 4.4 1.8 0.5 0.4 0.2 0.3 0.3 0.4 73.0 [.5-1.5) 1.0 1.0 1.4 1.9 1.7 1.5 1.4 1.2 1.5 0.9 0.8 0.3 0.4 0.4 0.3 0.6 17.3

TOTALS

C .5-31 2.5 4.414.213.912.811.710.2 6.1 5.9 3.7 1.3 0.7 0.6 0.7 0.6 1.0 90.3 [.5-4.5] 2.5 5.115.915.513.413.811.7 6.8 6.3 3.8 1.3 0.7 0.6 0.7 0.6 1.0 99.7

PROB. . .03 .05 .16 .16 .13 .14 .12 .07 .06 .04 .01 .01 .01 .01 .01 .01 1.00 (.5-4.5) DATA FILEDIN F2KWIMET.DAT

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TABLE 3: APPENDIX C

DCE MET DATA -STABILITY CLASS/SPEED VALUES USED IN B3 04 F2 GROUPS

Direction N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW TOTAL

A3KWIMET. DAT

PROB. 04 .09 .08 .06 .04 .07 .05 .05 .05 .05 .04 .05 .15 .09 .05 .02 1

83KWIMET. DAT

PROB. .03 .05 .05 .06 .11 ..09 .06 .04 .05 .03 .06 .09 .16 .07 .03 .02 1

C4KWIMET.DAT -

PROB. .02 .04 .02 .05 .08 .05 .04 .04 .05 .13 .28 .07 .05 .03 .03 .02 1

04KWIMET. DAT

PROB. .04 .06 .04 .05 .09 .05 .03 .05 .10 .15 .09-.09 .08 .05 .02 .02 1

E4KWIMET.DAT

PROB. .00 .09 .18 .23 .05 .05 .00 .00 .09 .09 .05 .09 .05 .05 .00 .00 1

E2KWIMET. DAT

PROB. .02 .05 .09 .07 .06 .10 .14 .16 .14 .06 .02 .03 .03 .01 .01 .01 1

F2KWIMET. DAT

PROB. .03 .05 .16 .16 .13 .14 .12 .07 .06 .04 .01 .01 .01 .01 .01 .01 1

B3 GROUP; (8.4 %)

PROB .04 .06 .06 .06 .09 .08 .06 .04 .05 .04 .05 .08 .16 .08 .04 .02 1.00

DATA FILED IN B3GKWMET.DAT

04 GROUP; (56.3 %)

PROB .03 .05 .03 .05 .08 .05 .03 .05 .08 .14 .14 .08 .07 .05 .02 .02 1.00

DATA FILED IN D4GKWMET.DAT

F2 GROUP; (35.3 )

PROB .02 .05 .11 .10 .09 .12 .13 .12 .11 .05 .02 .02 .02 .01 .01 .01 1.00

DATA FILED IN F2GKWMET.DAT

S

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APPENDIX D

DUPONT SAFETY AND OCCUPATIONAL

HEALTH POLICY

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: ..

0

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1. 211

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I

n the early 1800's, Eleuthère Irénée du Pont was building his

Company—and its reputation—on the manufacture of gunpowder. It was perhaps the most hazardous occupation in the country at that time . . . a line of business in which any error could result in a catastrophic explosion. No powder manufacturer could fail to recognize the dangers involved, but it was E. I. du Pont who took steps to make sure the workplace was safe.

Based on his firm belief in the value and rights of the individual, du Pont saw in his role an innate responsibility to provide the safest possible workplace, and to protect the health and safety of all his employees. These were the princi-ples on which his company was founded... principles that he put into practice from the earliest days of the Company's existence.

For example, he designed his first powder mills so that, in the event of an explosion, the force of the blast would be directed away from other mills—and away from the other workers. He tested gunpow-der formulations himself, before permitting any other employee to handle them. And no employee was allowed to enter any new or

rebuilt mill until top manage-ment—du Pont himself or his General Manager—first operated it safely. But the strength of E. I. du Pont's personal commit-ment to the safe operation of his company is exemplified by the fact that he and his family chose to live on the plant site, beside the mills with his employees, on the banks of the Brandywine River.

This active commitment to a safe workplace set standards of per-sonal conduct and management responsibility that became an inseparable part of the way the Du Pont Company conducts its business. It is a commitment which has been refined, expanded and improved upon by successive generations of management. And today, support of this commitment is evident throughout the Company, worldwide. The sections which follow highlight significant aspects of our corporate approach to safety, and present an overview of the comprehensive scope of today's safety and occupational health efforts.

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The Du Pont Philosophy

This Textile Fibers staple spinning opera-lion is engineered for

operator safety. A vacuum hose is used to draw new bundles of nylon threadlines into the automated

spinning equipment, where they are joined

together in a larger unit called a "rope'

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Following a standard safety practice for handling tools and equipment, this employee wears a leather glove while holding a vacuum hose. His safety glasses and short sleeves reflect other aspects othe Company :c program to reduce risks.

he underlying philosophy of ! today's corporate safety and

health effort is the same as that with which our Company began: our most valuable resource is our human resource; as such, it must be protected. This philosophy is supported by a written policy which states that:

"We will not make, handle, use, sell, transport or dispose of a product unless we can do so safely and in an environmentally sound manner."

Each department or site is respon-sible for developing and imple-menting plans and programs to ensure compliance with this policy. This requires a safety and health program which operates according to consistent and comprehensive principles. DuPont has established ten principles which are integrated into our approach to safety. principles which work together to keep employees safe and health on the job.

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Ten Pfinciples of Safety

Personal protection and equipment safety -

gohandinhand whenever maintenance

work is performed. This employee, wearing

protective gear specified for the job,

works on valves which have been

"locked and tagged out." The tags, signed

and in place, signify that the system has

been made inoperative and poses no danger

to the employee.

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1 All injuries and occupational illnesses can he prevented.

At DuPont. we believe that this is a realistic goal and not just a theoretical objective. Our safety performance proves this goal is achievable, as we have plants with over 1,000 employees that have operated for over ten years without a lost-time injury.

2 Management is directly responsible for preventing

injuries and illnesses, with each level accountable to the one above and responsible for the level below. This includes all levels, from the chairman, who is also the chief safety officer, through to the first line supervisor.

3 Safety is a condition of employment: each employee

must assume responsibility for working safely. In DuPont. safety is as important as production, quality, and cost control.

4 Training is an essential element for safe workplaces.

Safety awareness does not come naturally—management must teach, motivate and sustain employee safety knowledge to eliminate injuries. This includes establishing procedures and safety performance standards for each job or function.

5 Safety audits must be con-ducted. Management must

audit performance in the work-place to assess the effectiveness of facilities and programs, and to detect areas for improvement.

6 i'Jl deficiencies must he corrected promptly, either

through modthing facilities. changing procedures. bettering employee training or disciplining constructively and consistently. Follow-up audits are used to verify effectiveness.

7 It is essential to investigate all unsafe practices and

incidents with injury potential, as well as all injuries.

8 Safety off the job is just as important as safety on the job.

Du Pont was a pioneer in tracking the off-the-job safety of employees beginning in 1953. As a result, the Company initiated programs to dramatically improve off-the-job performance.

9 It's good business to prevent illnesses and injuries. Serious

illnesses and injuries involve tremendous costs—direct and indirect. The highest cost is human suffering.

10 People are the most critical element in the success

of a safety and health program. Management responsibility must be complemented by employees' suggestions and their active involvement in keeping work-places safe.

5

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equipment, such as this order picker, must

follow strict safety procedures.

To remove printed stock from a

warehouse shelf this operator must be

secured by a safety

Occupational Safety, Health and Environmental Quality: The Corporate Structure

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Aomprehensive and well-integrated approach to

establishing and maintaining the highest standards of safety and health is reflected throughout DuPont's organization. The corporate structure concretely represents how the Company car-ries out its policy that each product must be able to be made, used. handled, and disposed of safely and in keeping with appropriate safety, health and environmental quality criteria.

This policy is implemented and monitored by the Environmental Quality Committee (EQC), which was created by action of the Executive Committee in June. 1966. The function of the EQC is to recommend broad corporate policies in the areas of safety, health and environmental quality, and to offer advice to departments when a need is indicated.

To help coordinate Companywide safety and health, the EQC estab-lished the Occupational Safety and Health Committee.

It provides a communications link between the EQC and the indus-trial and staff departments on safety and health programs which are of concern to the Company or its customers. Activities cover dis-cussing and evaluating safety and health practices and problems common to the departments, providing current information on occupational safety and health legislative and regulatory develop-ments as they relate to Company interest, and making recommen-dations to the EQC on policies and procedures.

Through this and its other sub-committees, the EQC is closely

connected with the safety, health and environmental activities, concerns and programs in the industrial departments. The EQC also provides information, insight and recommendations to the Company's Executive Committee which develops the overall policies. The EQC and its subcommittees are an interactive, closely aligned network which allows communi-cation among departments. right up to the Executive Committee.

As members of the EQC, several Company departments play special roles in guiding and implementing safety and occupational proce-dures across DuPont:

The Engineering Services Division (ESD) of the Company's Engineering Department designs, tests and evaluates plant equipment and processes, and consults with sites on standards for process hazards, occupational health, noise control and many other areas. Engineering Design recommends solutions to control the noise, dust, fumes, vapors and heat stress encountered in manu-facturing areas.

Employee Relations' Medical Division conducts periodic physi-cal examinations of all employees, and monitors those exposed to certain toxic substances. The Medical Division also collects epidemiological data to uncover health problems and to supply disease rates for the Company.

The Haskell Laboratory for Toxi-cology and Industrial Medicine studies toxicity of chemicals used, made and sold by DuPont. Haskell tests about 500 substances a year to determine whether they are hazardous to occupational or environmental health.

7

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ince 1926, the Safety and Occupational Health Division

has surveyed site performance to ensure that safety principles are being followed, and has assisted sites in directing their safety efforts to achieve optimum perfor-mance results. Now, as then, the Safety and Occupational Health Division repnts a key support grouhich provides staff resources to assist in implementing the Company-wide safety effort.

Today, the Safety and Occupa-tional Health Division provides assistance through: Safety and Health Auditing, Consulting, and Workers' Compensation.

Safety and Health Auditing

Corporate auditors provide an independent assessment of the performance of each site. Occupa-tional health and safety audits are conducted on a Companywide basis to identify areas that need improvement, and to assist site management in developing programs to implement those improvements. Audits take place every 12 to 20 months, depending upon the site safety performance.

Consulting

Safety and Occupational Health consultants are available to all Company departments to provide guidance and help with any safety or occupational health problems that arise. They investi-gate serious accidents as well as advise on safety and fire protection

engineering for new construction or alterations to existing facilities.

Workers' Compensation This section provides a corporate level support group which directs and coordinates all aspects of Workers Compensation programs through individual plant sites. Legal and Finance Departments, and various state and Federal administrative agencies. As with all Safety and Occupational Health Division activities, the goal of this group is to provide a comprehen-sive and consistent resource base which will benefit employees.

General The overall responsibility of Safety and Occupational Health also includes:

Development and coordination of the Company's risk manage-ment policies and procedures.

Collection and analysis of safety performance data for both on- and off-the-job injuries.

Presentation of corporate safety awards to deserving sites, with safety prizes for employees.

Communication with govern-ment agencies, such as OSHA and NIOSH

'to keep up-to-date on

research and regulatory matters and to share DuPonts expertise in safety and occupational health.

Representation of the Company on committees of national organizations such as the National Fire Protection Association, the National Safety Council, and the Chemical Manufacturers Association.

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Sut' driving is an integral part of the corporate safety commitment, both on and off the job. .4/1 employees are required to use properly adjusted headrests and seat belts on Company business and encour-aqed to buckle up all the time.

T he key to Du Pont's.effective-ness in creating and main-

taining safe workplaces is the use of a balanced approach to safety. The concept is easy to understand and apply. Three elements interact in every workplace that give rise to the risk of injury. They are (1) equipment design. (2) materials hazards, and (3) peoples' actions. To control risk, all three elements must be ddressed and applied in the development and practice of a safety and health program.

Scientific, industrial and govern-ment regulatory groups have made great progress in advancing safe equipment design, and reduc-ing the incidence of exposure to materials hazards. But safety lies primarily in the hands of em-ployees themselves. Programs must concentrate on each individual employee, and the need to create an attitude or state of mind con-ducive to safe actions.

To this end, our employee safety effort is founded on management commitment and employee involvement. Further, our safety program emphasizes both "on-the-job" procedures and "off-the-job" awareness of such issues as seat belt use, defensive driving, and household safety. We believe the employee whose safety awareness extends to all facets of his or her life will contribute most consis-tently to safe actions on the job.. safe actions being the most critical of the three elements in a balanced approach to safety.

11

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Accomplishments and Future Challenges

Twenty-four hours a day, operators in this

process control room monitor pressures, temperatures, flow

rates and other aspects of their totally

automated polymer processing operation. Any situations which

exceed established tolerances are

detected and corrected immediately.

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D uPont has continually been a leader in industrial safety

with safety performances that. according to National Safety Council statistics, showed we were far safer than the average chemical company and many times safer than the average industrial company. But no matter how good our past records, safety is always an issue that is only as good as the current moment tells us it is. Injuries and illness are no respecters of past achievement—they are potential problems that could strike at any moment.

Because Du Pont is intent not only on maintaining its outstanding safety performance but also on improving it, corporate safety studies are conducted to identify opportunities which could increase the effectiveness of our safety efforts as we progress.

Studies focus on identifying specific areas for substantial improvement in injury and risk control, and analyzing the most effective risk control methods. Study findings consistently sup-port Du Pont's traditional safety principles and practices, showing that there exists the least number of injuries where there is a demonstrated management com-mitment, vigorous audit programs, the attitude that all injuries can be prevented, and maximum employee involvement.

"Du Pont recognizes the challenge to meet and surpass its own outstanding safety performance record. This is a goal shared by management and employees—a goal the Company will work toward day in and day out, to assure the safest, most healthful workplaces possible. Safety and Occupational Health is and will continue to be a commitment in action at Du

E.C. Jefferson Chairman

13

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:

1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

MEMPHIS INJURY PROFILE

.. - -7 -

/ - - .....

// .........

................ /

1983 1984 1985

1986 1987

MEMPHIS LWC

MEMPHIS TRR----

MEMPHIS ALL INJURY

DUPONT TRR ........

25.0 I

20.0

15.0

10.0

5.0

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Th

• -

-Th

.-

-

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DNV RISK ANALYSIS EXPERIENCE

Listed below are some of the studies carried out by DnV's Technical Services Group which are relevant to this PRA.

Quantified Risk Assessment Studies

- Ammonia/Urea manufacturing plant - LPG extraction plant - LPG storage and distribution terminals - Chemical storage and distribution terminals - Cross country LPG pipeline system - Ammonia pipeline and ship unloading system - Lube oil formulation, storage and distribution facility -- Ammonia manufacturing plant - VCM and liquids storage terminal - Chlorine storage injection facilities - Detergents manufacturing plant

Hazard and Operability Studies

- LPG extraction plant - Sodium cyanide plant - Chlor-alkali plant - Ammonia storage, pipeline and import/export system - Oil/Chemical storage and distribution terminals - Off-shore oil/gas production facilities - LPG terminal

Environmental and Risk Management Studies

- Emission monitoring studies (e.g. VCM) - Numerous safety audits and fire safety studies - EIS for onshore oil import facility - Risk review of pesticide formulation plant.

The study team, Mr J.R. Castleman, Principal Engineer, and Mr A.J. Irvine, Senior Chemical Engineer, have conducted the above risk studies including studies in the Kwinana area and on sodium cyanide, hydrogen cyanide, and ammonia.

During this study Mr Castlèman inspected Du Pont Sodium Cyanide plants in the USA and reviewed technical information, operating experience and safety systems used by Du Pont.

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j

j

c APPENDIX F

AMMONIA SOURCE/RELEASE MODELS

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DUPONT NH3 RELEASES: SOURCE/RELEASE MODELS

SUMMARY OF DNV CALCULATIONS AND ASSUMPTIONS

PRESSURIZED, LIQUEFIED AMMONIA

1 . Product temperature - 200C Product pressure - 800 kPa Flew rate - 4.5 te/h 74 kg/rn = 1.25 kg/s Pipeline I.D. - 50mm Pipeline length - 2000m Pipeline hold-up - +/- 2.63 te NH3

2. Pipeline rupture: sudden, full bore fracture of line.

Total quantity released depends on:

- flash - time to pump s/d and valve isolation - gravity flow after s/d - subsequent evaporation of line contents.

Cloud formation:

- 20% flash as pressure drops - spray/aerosol formation -> evaporation - evaporation from heat absorption and wind effects.

New effect: 80% of instantaneous release will form source cloud.

Source cylinder (for DENZ dispersion model).

- Air adiabatically saturated with NH3 @ -720C - 6% wt NH3 in air - s.g.• = 1.35 x 1.2 = 1.62 kg/rn3 - Dilution factor 8.5 : 1

Air : NH3 -

Source cylinder volume calculated, height = radius.

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Pipeline major leak:

- hole diameter 20% of bore : 10 mm - conventional orifice flow calculation - duration depends on detection and ESD times - some gravity flow after ESD

Cloud properties for CRUNCH dispersion model:

- 80% of release quantity will form cloud (mechanisms as above)

- cloud s.g. 1.35, 8.5:1 dilution.

Pressurized vessel: large hole in vapour space/rupture (e.g. buffer storage vessel and vaporizer).

Same mechanism as in 2 above: vigourous bulk boiling will occur with (most if not all) of vessel contents being flung

C into the air.

Nett effect: 80% of instantaneous release will form source cloud.

Pressurized vessel: small hole in vapour space.

Pure vapour may escape at sonic velocities, giving buoyant plume.

Assume cloud is buoyant.

Pressurized vessel: hole in liquid space.

Same as 3 above - dense cloud formed, containing 80% of released ammonia.

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7. Surface roughness:

The surface roughness length is a measure of the friction between the atmosphere and the earth's surface. Surface roughness length may vary from less than 1 mm over calm water, smooth ice, or smooth mudflats to over 1 m for the centre of cities. The proposed pipeline route and surrounding terrain is low lying land surrounded by a variety of landscapes and buildings ranging from minor vegetation to large warehouses and chemical plants.

Surface roughness is estimated to be in the range of 0.1 to 0.3m, therefore a length of 0.1 m was chosen for gas dispersion modelling as a value which would give reasonable conservative results.

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APPENDIX G

SUMMARY OF MAJOR RELEASE INCIDENTS

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Du Pont Sodium Cyanide Plant

Risk Ranking

FREQUENCY CONSEQUENCE

HIGH MED LOW VERY LOW

High

Reactor Bursting Discs X Flare Vent Line Leak X Flare Flame Out X

Medium

Flare Header Leak X Warehouse Incident X Reactor Feed Line X

Low

Vaporiser X X Vaporiser Feed x Storage Vessel X X Ammonia Pipeline Minor Leak X X

Very Low

Ammonia Pipeline Major Rupture X

Extremely Low

Natural Gas Supply X X

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APPENDIX H

RELEVANT COMPUTER PRINTOUTS

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RISK CONTOURS

The contours show the riskto an individual permanently located at a location near to the facility. The contour frequency e.g. 1 x 10 p.y., is the sum of the risk (frequency) of a given effect such as fatality at a point from all events which could impact at that point.

The contribution from each risk event to the contours is calculated as the product of the risk event frequency and the probabilities associated with the occurrence of the given impact at each point on a location map.

For fatality from toxic gas release, the risk of individual fatality is assessed as:

R = R event. P lethal dose (x,y). P wind direction (each weather category [stability, speed]).

There are a number of further factors considered in each of the

above components. For example:

The event frequency is a frequency associated with a selected class of consequence e.g. rupture, major leak, minor leak,

etc. These are selected to be representative in terms of

overall risk profile.

The probability of exposure to a lethal dose involves the detailed assessment of toxic exposure in terms of the dose presented by the release at each location, and the probability of an individual at each location suffering a fatal response to the dose received.

The probability that a release will impact upon each location is assessed from the probability of lethal dose within the cloud envelope as calculated from the cloud dimensions, and downwind dose integrals for each weather category (stability and wind speed) and the probability of wind direction for

each weather category.

lot

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The calculations of toxic dose use the detailed dispersion model output files of the programs DENZ and CRUNCH to calculate the dose (C2t) integral, probit values for average and vulnerable populations and the corresponding percentage fatality.

The probability of death at each distance downwind is calculated using the percentage fatality and probability of exposure to that dose for a range of upwind and downwind distances. These probabilities are filed for each toxic release cloud for the representative weather categories considered, for use in the risk calculation at each map grid point. Each probability file contains from thirty to forty values corresponding to distances downwind. The risk calculation interpolates linearly between the nearest probability file values in determining the probability value for each grid point.

In the risk contouring subroutines the contour line is located between the grid points with nearest values above and below the contour value and the exact position on the grid determined by linear interpolation.

CRITICALITY AND SENSITIVITY:

In this study, a number of computer runs were carried out on the data as it was being compiled to determine criticality of the various inputs. The results are directly proportional to factors such as frequency, probability and distance within certain ranges. The multi-factorial nature of the calculation results in limiting conditions where some factors e.g. probabilities and concentrations, reach such small values that the resulting risk becomes insignificant or non-credible.

For example, beyond a certain distance the zone of harmful concentrations within gas cloud resulting from an instantaneous release will reduce as the cloud disperses to harmless concentrations. The exposure time associated with concentration range will also decrease with the resulting dose and corresponding fatality level decreasing ultimately to zero.

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As this point is approached, other factors such as event frequency, probability of wind direction, etc. will have less influence on the final result. The risk contours are most sensitive to the downwind dose distances, and location of release sources. Certain weather conditions, particularly very stable conditions lead to greater distances, especially for continuous releases. Risk frequencies and probabilities, while important close to the release point, become less critical with distance. For example, if all the event frequencies were underestimated by a factor of ten, the outer 10 contours would be extended by no more than 75 metres, less than 20% increase.

Examples of the gas dispersion results, percentage fatality at the cloud centre for various distances downwind, probability of fatality for various distances from release (not necessarily within the cloud), and charts of these probabilities for the different weather categories are given in this appendix.

NOTE:

The information referred to in the last paragraph has been made available to the EPA. Due to its technical nature and for proprietary reasons the detailed printouts are not generally available. The most critical results are given in the following graphs of fatality risk at various distances for given release scenarios.

çEk

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1.25 kg/s Continuous Ammonia Release Probability of Fatality (given release)

at Distance m from source (Stable-2 m/s)

Probability of Fatality given release

0.4

0.2

20 40 60 80 100 120 140 Distance from Source (m)

Average wind (Notel) Most prob w-dir (SE)

1. Assurnea average wind direction proby

lot

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1.25 kg/s Continuous Ammonia Release Probability of Fatality (given release)

at Distance m from source (Neutral 4m/s)

Probability of Fatality given release

we

0.4

0.2

re 10 20 30 40 50 60 Distance from Source (m)

- Average wind (Notel) - Most prob wdir S-SW

1. Assumes aver.8QO wind direction prob'y

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1 Toflne Instantaneous Ammonia Release Probability of Fatality (given release)

at Distance rn from source (Stable 2m/s)

08

0.6

0.4

0.2

0 0 10 20 30 40 50 60

Distance from Source (m)

--- Average wind -Note 1 - Most prob wdir (SE)

1, Assurnea average wind direction prob'y

70 -

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1 Tonne Instantaneous Ammonia Release Probability of Fatality (given release)

at Distance m from source (Neutral 4m/s)

rFULfliLJIlIly UI riuiiity IV311 ieiease

0.8

0.4

0.2

0' 0 10 20 30 40 50 60

70

Distance from Source (rn)

- Average wind -Note 1 Most prob wdir 8-88W

1. Aseurnes everaç'je wind direction proby

SKfr

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APPENDIX I

MODELS/METHODS USED IN

CONSEQUENCE CALCULATIONS

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DESCRIPTION OF MODELS:

Gas Dispersion Models Description

Field experiments on dense gas dispersion and observation of accidental releases have established beyond doubt that the dispersion of dense gases follows a different mechanism from that of neutrally buoyant clouds, therefore mathematical models developed particularly for heavier than air gases must be used in assessing atmospheric dispersal.

Several calculation methods are used by DnV to model gas dispersion (both dense and buoyant).

1) ARCON 3

ARCON 3 (Air Relative Concentration) is a DnV in-house computer program for modelling the dispersion of a continuous plume of buoyant vapour. Relative concentrations are calculated using standard Gaussian diffusion parameters for a range of (Pasquill) atmospheric stability categories.

DENZ

DENZ is a computer program for the dispersion calculations of dense toxic or explosive gases in the atmosphere. it was developed by the U.K. Atomic Energy Authority (A.E.A.) and is used for instantaneous or "puff" release cases. DENZ is used by the U.K. Health and Safety Executive for QRA involving dense gases.

CRUNCH

Also. developed by, the U.K.A.E.A., this program models continuous releases of denser-than-air vapours into the atmosphere. CRUNCH is used by the U.K. Health and Safety Executive for QRA involving dense gases.

A number of other short-cut gas dispersion techniques, such as nomograms and data tables applying to individual gases, are used as a back-up for the above programs.

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Assumptions of the Heavy Gas Dispersion Models

- The dispersing cloud or plume moves over flat terrain or water.

- The ground (or water) has constant roughness and thermal properties.

- There are no obstructions to the wind or moving cloud.

- The contaminant gas undergoes no chemical or physical reaction during dispersion.

- The cloud has a flat top and the concentration of contaminant is uniform across the cloud.

In an instantaneous or "puff" release, the cloud can be expected to adopt a pancake shape and spread radially relative to its centre while simultaneously moving with the wind. This shape has been observed in a number of field experiments. The idealised cloud shape for the model is assumed to be a vertically oriented cylinder with flat-top and of radius R and height H, both of which change as a result of gravity spreading and air entertainment.

In the case of a continuous release, the cloud is a narrow plume which spreads laterally due to gravity. The plume is assumed to be steady and rectangular in cross-section (box) with its axis along the wind direction.

Figure 5.1 illustrates idealised plume/cloud shapes for both models. When specific conditions of cloud spreading and/or cloud concentration are satisfied, the models then treat dispersion as buoyant (or Gaussian).

Where there is some doubt about the nature of the release (e.g. whether it is instantaneous or continuous) both DENZ and CRUNCH runs are carried out for the release quantity and the conservative (pessimistic) results taken for hazard distances.

1

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Toxic Gas Dispersion Risk Contour Model Description

The risk analysis method treats toxic gas dispersion in the following steps:

Analyse release scenarios to examine the significant factors affecting gas release volumes, conditions, flow rates, durations and dynamics.

Select sets of release conditions and resulting release rates to represent the range of release risk including worst credible release scenario, minor releases and continuous release. -

Select suitable dispersion models for the release conditions including buoyant or dense gas models and instantaneous or continuous release models as most appropriate.

Analyse meteorological data to determine predominant conditions as well as the most unfavorable (but credible) conditions for consequence calculations over a range of representative classes of conditions.

From the consequence and dispersion results prepare suites of data for risk contour modelling. The Veritas risk map program utilises gas dispersion information including the shape and dimensions of hazard zones under - the various representative classes of meteorological conditions for each release event.

The dispersion results are ranked and analysed against the meteorological data to provide a basis for determining the meteorological conditions which will produce particular hazard zones and ranges and the resulting frequency of occurrence functions are derived. After analysis of stability, wind speed and direction to confirm suitability of the data for the range of significant gas release scenarios, the meteorological data is input to the risk map program. The data is represented by wind direction probabilities for sixteen directions and a cumulative probability function for stability and wind speed ranging from the most unfavourable conditions to all conditions.

\ I

4Q'

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7. For toxic gases, the program determines the integrated dose (function of C2t) received at each downwind point.

The probability of exceeding a lethal dose at each point across the cloud (crosswind) is determined and the probability of death at each distance downwind determined from the probability of exceeding a lethal dose within the cloud and the probability of being within the cloud. The functions which determine the probability of death are:-

- the actual cloud shape and concentrations -

the time of exposure to each concentration downwind and crosswind.

The probability that a person will be within a potentially lethal cloud, given random wind directions, will range from 1 for distances less than the upwind cloud limits to zero beyond the downwind limit of lethal dose. This is calculated accurately from the cloud data. The probability of wind direction, wind speed and stability conditionsis included in the individual and group risk calculations, where 16 wind directions and the major stable neutral and unstable weather grouping probabilities are applied.

In the risk map program each point (usually on a 45 x 60 grid) is checked for proximity to each potential release point and the risk frequency, if any, for exceeding the hazard level is determined and summated. The risk frequency of impact from a given event at the point will depend on release frequency, the probability of conditions occurring under which the hazard level would reach the point concerned, and the wind direction probability and the probability of death at each point. The shape of the hazard zone including upwind, downwind and crosswind distances at each grid point is accounted for in the program by cloud hazard zone shapes determined from the gas dispersion results. By utilising the actual hazard zone shapes, more accurate risk levels are determined than by simpler methods used in some other programs.

Individual risk of fatality combines the frequency of impact with the probability of death at each point. The Individual Risk of Fatality is the sum of risks of fatality from all sources at each point.

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Individual risk contours are then plotted to join points of equal risk (or frequenc) at the criteria levels e.g. 1 x iø p.y., i x io p.y., 1 x iø p.y. for relevant levels of lethality for exposed groups as follows: e.g.

The contours are determined by linear interpolation between the nearest values to the level of interest.

The contours therefore show the expected frequency of a potentially lethal exposure to an individual at greatest risk.

Group risk is calculated at every grid point where population density and lethality factor are combined to calculate the number of fatalities associated with each risk source and wind sector.

The number of fatalities (N) is cumulated for each source and each of 16 wind sectors taking into account the actual hazard zones for the different representative meteorological conditions.

The frequency (F) associated with each number of fatalities (N) is calculated from the risk event frequency, the probability of the wind blowing in the sector under consideration, and the probability of the requisite

J meteorological conditions occurring. The Frequency associated with the maximum expected fatality rate (F x N) is assigned to the (N) Value for the source and sector.

Finally after all grid points, wind sectors and risk sources have been considered, the F, N pairs are sorted into descending order of numbers of fatalities (N) for plotting of the F, N curve.

Program Options are available to handle special group risk implication of fire, explosion and other hazards.

The program option for Flash Fire Group Risk Assessment is described below.

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FLASH FIRE GROUP RISK MODEL DESCRIPTION

The model describes the "population" at risk, as used for assessment of risk to people. However, any value system including property value, criticality of plant, total loss value etc. may be used to provide appropriate terms of output.

1. The number of people represented by the grid poInt is determined from a population map together with a factor (PRF) "presence factor" which enables the population expected to be present at the time to be calculated. In addition, for risk events where the distance to 50% lethality is less than half the grid distance a correction factor called AF "Area Factor" is also calculated and included where:

AF = (Hazard Distance (50% Lethality)2 GRID LENGTH

This allows for situations where the hazard zone will be less than the grid square and hence not all of a distributed population will be at risk. Where the distance to 50 % lethality is greater than half the grid distance a default value of 1 is used. The Area Factor has been checked over a range of hazard distances and locations and found to provide a reasonable approximate value for most situations.

Where use of the above Area Factor would not be appropriate, e.g. non-uniform population distribution; alternative distribution functions may be used or input data locations may be selected manually to minimise error or the grid size or registration changed if this is considered to be appropriate.

2.

/

The number of fatalities for each grid square (for each risk event and source location) is as follows:

NF = Pop (x, y). PRF . AF . Lethality.

In the case of flashfire the Lethality is taken as 1 for people outside and estimated for indoor populations.

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S

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The Risk Frequency of the risk event at grid point (x y) is determined as follows:

R = F (event) x Probability of effect reaching grid point (x, y)

The probability of reaching the grid point takes account of the probability of atmospheric conditions and the probability of ignition that would enable the point to be within the hazard zone.

Using the same method the program then considers every other grid point within each hazard zone. It will be appreciated that for a flash fire the hazard zone will be the area affected by the actual flash fire or its immediate consequences. In most cases for fatalities this is assumed to be the area contained within the estimated lower flammable limit boundaries. For a moving gas cloud on flat J terrain resulting from the worst case assumption of near instantaneous release of pipeline contents, the actual hazard area for a flash fire will be approximately a circle of radius equal to the cross-wind radius of the cloud as it moves out to its maximum down-wind location. This circle will initially increase to its maximum and then decrease to zero as the cloud disperses and dilutes to below the LFL.

In order to ensure that each FN pair (Frequency x Consequence data set) is represented reasonably accurately in terms of both frequency and number of fatalities, the following procedure is adopted.

The program accumulates those fatalities in each grid square where the frequency is within 20% of the frequency associated with the maximum expected fatalities for the hazard zone. Where •frequency changes occur, supplementary data pairs are commenced to accumulate fatalities at the corresponding frequency rates. The frequency for each cumulated FN data pair is the frequency rate corresponding to the largest number of expected fatalities (Fatalities x Frequency) This in effect is the greatest contribution to risk for the event and hazard zone considered.

When all grid points have been checked for all risks events and all source locations, the data is stored in a file of risk sources and their risk consequences as FN Pairs.

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These data pairs are then sorted into descending order of number of fatalities, and the cumulative frequency at each descending number of fatalities is calculated.

The data is then filed for a number of points by specifying plotting intervals (approximately 1% decrements), and the points are plotted on an FN Curve.

In developing the program, numerous checks and enhancements have been carried out. It will be appreciated that where such large numbers of calculations are involved some simplifjcations must be maintained in order to keep running times and file sizes within workable limits.

Even a moderately simple calculation routine eg. to increase precision of calculation within each grid, can result in an increase in running times from hours to days. Such running times would then limit the chances for further analysis, sensitivity studies and the like.

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APPENDIX J

ENYIRONMENTAL PROTECTION AUTHORITY

GUIDELINES

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DUPONT SOLID SODIUM CYANIDE PLANT, KWINANA

DRAFT EPA GUIDELINES FOR A PRELIMINARY RISK ANALYSIS

Comment: These guidelines cover preliminary risk assessment requirements for any proposed industrial plant. The amount of detail required for a particular project will vary with the complexity of the project and the nature of the materials being handled on the site. A low cost project handling a highly toxic chemical could require a more detailed preliminary risk assessment than a high cost development in which materials of low hazard were to be produced.

SUMMARY

The document should be a clear and concise summary of the preliminary risk analysis.

INTRODUCTION

Background to this study.

Study aims and objectives

General nature of the project.

Philosophy and approach to risk assessment. Include explicit definitions of "risk" (as test and mathematical) in the context referred to in the EPA guidelines.Describe the background of the firm performing this risk assessment particularly the background and previous of the members of the firm conducting this study with special reference to working knowledge of this type of plant-.

Risk standards and guidelines.

Discuss EPA guidelines on the "acceptability" of risk levels in W.A.

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3. PROJECT DESCRIPTION

Site location and environment of the project site including topography.

Meteorology including wind speed and direction, atmospheric stability, surface roughness length and any other parameter relevant to risk analysis. The windspeed - stability class frequency distributions by wind direction used in risk calculations should be shown. If these have been condensed from a more precise data form, the method of reduction should be described and justified in the Appendices.

Process description, including flow diagrams, storages, inventories of major vessels and overall plant layout. There should be particular emphasis on safety features (eg. bunding of storage vessels, shutoff valves on major precess lines, separation distances to avoid domino effects etc.) Details of the proposal should be sufficiently advanced to enable meaningful risk assessment to be performed.

Other parameters in the surrounds of the chosen site which need to be considered in the risk analysis.

4. FACTORS AFFECTING SITE SELECTION AND RISK TO PUBLIC AND NEARBY FACILITIES.

Hazardous material properties.

Hazards associated with this type of plant.

Hazards of process, storage and transportation.

Review of safety records of similar facilities.

Review of engineering codes and standards.

Review of safety engineering design.

Review of other factors such as domino effects, export loading, shipping etc.

S

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t / 5. RISK ASSESSMENT

i) Methodology. Outline the method used to quantify risk from the proposal as per 5 ii) to 5 v).

) ii) discussion of general safety assumptions used for risk calculations such as safety engineering design, management and operation aspects, safety audition etc. Refer to a complete list of relevant standards, codes of practice etc. to be listed in the Appendices. The proponent should be prepared to endorse these assumptions as "commitments".

Checklists of hazards identified as having consequences leading to possible fatalities outside the plant site and derivation for data consequence and risk calculation. The contents of this list are given in Attachment #1

Description of calculation of, consequences of failure referencing methods/models, input data and assumptions used. The Appendices should contain a more comprehensive description of the methods/models including values of and references for all coefficients.

Presentation of individual risks levels associated with this plant and quantitative ranking of those hazards which contribute to the risk near the 1 x 10'6/yr individual risk level.

The list of hazards in the 'checklist" (5 iii)) should be ranked in terms of their potential consequences off-site and these consequences should be quantified using tables of distance versus concentration, distance versus explosive probability in each direction (if applicable), and distance versus fatality probabilities.

Discussion of how the hazards contributing most to risk (5 v)) and the hazard having the most serious potential consequences (5 vi)) may be reduced/minimised. Relevant factors to consider may include the installation of safety related equipment, alternative methods of - storage mlnirnisation of inventories, plant equipment layout specific recommendations on aspects to be incorporated in emergency planning etc.

Incorporation of the individual risk levels for this plant (5 v)) into the cumulative risk levels derived in the "Kwinana Cumulative Risk Study" (Technica 1987) for existing industry in the Kwinana region, and discussion on these future accumulated risk levels with reference to the EPA guidelines for risk acceptability. -

taj

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CONCLUSIONS.

Summary of results of risk assessment and conclus±ons as to site acceptability with special mention of any recommendations commitments which impact on the site acceptability.

APPENDICES

- Toxicity data.

- Bulk meteorological data presentation/reduction and explanations.

- Table of generic or unit failure frequencies used, fully referenced. Tables of failure frequencies and descriptions of their derivation are given in Technica (1987). Should the proponent wish to use failure frequencies other than those used in that study, their source must be clearly stated. In such cases the EPA will request that the proponent provides to the EPA the relevant literature from which the alternate values were obtained, in order to verify that their use is justified.

- Tables of all probabilities used in risk calculations, fully referenced. In case of probabilities of Ignition of flammable vapour clouds, these should vary spatially as a function of land use (as per Technica, 1987),

- Summary of major release incidents associated with this type. of plant.

- Relevant computer printouts.

- Detailed description of all models/methods . used in consequence calculations (see 5 (iv)).

ATTACHMENT #1

CONTENT OF "CHECKLIST OF HAZARDS"

Item of plant, or class of items (eg. storage vessels, large pipes, small pipes etc.) with similar characteristics which can be treated tether. Include details of volumes, flow rates, diameters etc. and details of proposed safety features describing their effects.

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Page 123: PROPOSED SODIUM CYANIDE PLANT Preliminary Risk Analysis€¦ · A Preliminary Risk Analysis has been carried out for the proposed Du Pont solid sodium cyanide manufacturing plant

Total failure frequency for the item or class of items (not adjusted to reflect any safety features which may fail).

For each significant event which may arise from the failure (eg dense cloud, explosion etc.) which may extend beyond the plant boundary, provide the following information:

- Describe event including type of failure, physical state of substance release, subsequent dispersion, ignition etc. Generally treat two cases, full and partial failure for each event type, to capture the full frequency.

- Frequency of event case, Show calculation using failure frequency for release case multiplied by the probability of subsequent phenomena (eg. ignition/explosion) resulting. Fore each case, provide the following:

Event case duration.

Event case release rate or instantaneous release mass. Release rate and duration of contaminants subsequently entering the atmosphere.

If safety devices which have non-zero failure probability are proposed to reduce frequency or release rate/quantity, then provide the following:

Failure rate per demand for safety device. . Modified failure frequencies and flow rates for safety

device(s) working and not working.

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