Fire Modeling Applications in FHA’s Gaines E. Bruce, P.E., SFPE WSMS-Mid America 105 Mitchell...

Fire Modeling Applications in FHA’s

Gaines E. Bruce, P.E., SFPEWSMS-Mid America

105 Mitchell Road, Suite 200Oak Ridge, TN 37830

[email protected]

Gaines E. Bruce, P.E., SFPEWSMS-Mid America

105 Mitchell Road, Suite 200Oak Ridge, TN 37830

[email protected]

•Washington Safety Management Solutions, LLC

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Fire Modeling Applications in FHA’sFire Modeling Applications in FHA’s

What is a Fire Model?

Model is a term applied to many physical and mathematical procedures designed to simulate reality.

Fire Growth Model is mathematical procedure developed to estimate the change in the environment of a space or building caused by a fire in that space that varies in intensity and/or involvement with time.

Typically models involve the simultaneous solution of two, or more, differential equations. Some involve many variables and can be quite complex.

Basically three types of fire models:

Zone Model

Field Model

Hybrid Model

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Zone Model:

Usually divide each room into spaces or zones:

Upper Zone contains hot gasses produced by fire Lower zone contains the source of air for combustion

Zone sizes change during course of fire. Upper zone can expand to occupy almost entire room space

Most of models that can run on PC are Zone Models

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Fire Modeling Application in FHA’sFire Modeling Application in FHA’s

Field Models:

Usually requires large-capacity computer work stations or mainframe computes.

Divide the space into many small cells (frequently tens of thousands)

Much more detail than zone models

Solves fundamental equations of mass, momentum, in a space that is divided into a grid of small-volume cells.

Hybrid Model:

A model that uses elements of both zone models and field models

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What Fire Models are available to the general industry?

More than a few, here are a few of my favorites.

Fire Dynamics Tools (FDTs) [NUREG-1805]• Preprogrammed Excel spreadsheets of basic first order relationships published in

industry literature such as SFPE Handbook of Fire Protection Engineering.• Cost: Free, download from NRC website

CFAST (Consolidated Fire and Smoke Transport)• Zone Model• Cost: Free, download from NIST website

FDS (Fire Dynamics Simulator)• Simplified Field Model• Cost: Free, download from NIST website

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Where does fire modeling fit into an FHA?

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Here is part of what we think a Fire Hazard Analysis (FHA)

is about

FHA’s are a thorough analysis of the fire potential in a facility.

FHA’s are normally performed on facilities which are categorized as a high industrial risk.

Serves as the basis to support other Safety Analysis reports.

Provides quantitative analysis of fire growth and impact.

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Here is the FHA Outline We Use

ACRONYMS/DEFINITIONS

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Purpose/Objective/Scope

1.2 Limitations of Assessment

1.3 Approach and Assumptions

1.4 Facility Use, Function

1.5 Calculations and Computations

Ok, a model may be a calculations so maybe something here?

1.6 Document Review

1.7 Lessons Learned

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Here is the first paragraph from our application guide for Section 1.5

Establish the extent to which the FHA will include calculations and/or fire modeling. If special methods or calculations are utilized, identify them but do not provide a detailed description. If computer generated calculations and/or models are included, discuss the Validation and Verification of those computer codes.

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2.0 DESCRIPTION OF FACILITY, EQUIPMENT AND PROGRAM

2.1 Description of Facility

2.2 Minor Facilities

2.3 Description of Critical Process Equipment and Programs

2.4 Description of High-Value Property

2.5 Description of Operations

2.6 Fire Barriers

3.0 LIFE SAFETY

3.1 Types of Occupancy

3.2 Means of Egress

3.3 Interior Finish Materials

3.4 Emergency Lighting and Exit Signs

3.5 Security Interface

3.6 Occupant Notification System

3.7 Section Summary

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4.0 FIRE PROTECTION

4.1 Water Supply and Distribution System

4.2 Fire Suppression

4.2.1 Sprinkler System(s)

4.2.2 Standpipe Systems

4.2.3 Other Automatic Extinguishing Systems

4.2.4 Portable Fire Extinguishers

4.3 Protective Signaling Systems

4.3.1 Fire Detection System

4.3.2 Manual Fire Alarm System

4.4 Fire Department and Fire Brigade Response

4.4.1 Pre-fire Plans

4.4.2 Access to Facility by Fire Fighting Apparatus

4.4.3 Fire Department Description

4.4.4 Mutual Aid Response

4.4.5 Emergency Planning

4.5 Defense-In-Depth

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5.0 FIRE HAZARDS5.1 Discussion of Fire Hazards

5.1.1 Limits on Combustibles

5.1.2 Control of Ignition Sources5.2 Impact of Natural Hazards on Fire Safety

5.2.1 Earthquake

5.2.2 Flood

5.2.3 Lighting

5.2.4 Windstorm

5.2.5 Wildland Fires 5.3 Analysis of Potential Fire Scenarios

OK, determining fire impact and bounding condition may be a good application for fire modeling.

5.4 Exposure Fire Potential 5.5 Potential for a Toxic, Biological, or Radiation Incident

5.5.1 Criticality, Radioactive Materials, and Contamination

5.5.2 Chemical, Corrosive Agents, and Other Special Hazards

5.5.3 Recovery Potential5.6 Water Runoff/Containment of Liquids

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Here is what our application guide says about Section 5.3

Reference the facility fire areas and locations, as defined in the facility description, for property damage limitation. Develop the likely fire accident scenarios for each fire area. Potential fire scenarios will be used to determine flame spread, the consequence of a fire, and the effects of environmental and radiological releases. Review the scenarios described in other SB documentation to assure there are no conflicting descriptions. If conditions have changed or SB documentation scenario descriptions are unrealistic, describe the discrepancy and why the current evaluation is valid.

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6.0 FACILITY DAMAGE POTENTIAL 6.1 Maximum Credible Fire Loss (MCFL)6.2 Maximum Possible Fire Loss (MPFL)

7.0 PROGRAMMATIC REVIEW7.1 Evaluation of Administrative Controls in Use and Compensatory Measures7.2 Status of Findings From Previous FHAs7.3 Exemptions and Equivalencies

8.0 SUMMARY OF IDENTIFIED DEFICIENCIES8.1 Findings and Recommendations8.2 Requirements8.3 Improvements/Observations (Best Practices)

9.0 SUMMARY/CONCLUSION9.1 Summary9.2 Conclusions

10.0 REFERENCES

11.0 APPENDICES (If applicable)

12.0 ADDENDA (If Applicable)

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Conclusions:

Fire modeling can best be use within an FHA to help define the bounds of a fire scenario and add some degree of realistic evaluation.

A well defined fire scenario can be of assistance to the DSA team in the development of accident scenarios for evaluation.

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In section 1.5 of our FHA’s we must address fire model validation if we use any fire modeling within the FHA.

Question: What existing V&V is available for our fire models?

Answer: I never though I’d say this, but “thank heaven for the Nuclear Regulatory Commission”.

NUREG-1824

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Citation for NUREG 1824:

Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications, Volume 1: Main Report, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research (RES), Rockville, MD: 2005 and Electric Power Research Institute (EPRI), Palo Alto, CA. NUREG-1824 and EPRI 1011999.

(Note: Seven Volumes in All)

This NUREG is the first effort to document the verification and validation (V&V) of five fire models that are commonly used in Nuclear Power Plant applications. The NUREG was developed in accordance with the guidelines that the American Society for Testing and Materials (ASTM) set forth in Standard E1355-04, “Evaluating the Predictive Capability of Deterministic Fire Models.” The results of the NUREG V&V are reported in the form of ranges of accuracies for the fire model predictions.

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Results from NUREG 1824:

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So What is the bottom line?

Our approach is to use as simplistic a model as possible to help assess the magnitude of selected fire parameters. So in general, we use nothing more sophisticated than the NUREG 1805 FDTs spreadsheets.

The spreadsheets are easier to defend since they are basically equations taken from industry literature that can be referenced.

If uncomfortable with using the spreadsheets, the preliminary assessments can be performed with then and then a formal hand process can be documented with less effort.

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Here are a few examples:

From the K-25/K-27 Facility FHA’s –Scenario forklift fuel pool fire impacts MAR stored on wooden pallets

20-gallon spill is assumed capacity of forklift tanks

53 ft2 (about 7 1/4 ft square) in order for a fire to last for at least 5 minutes

About 0.64 in (a little over 5/8 in) pool depth

Need cooperative building to confine to this depth and expose pallet of MAR

the fire from the hydrocarbon fluid alone would be about 7.3 MW

If the pallet is ignited, an additional 750 kW would be added (single pallet on floor) {best guess from Hanford pool test and SFPE handbook}

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if there is pallet to pallet contact), fire propagation along a pallet row could be expected

If the MAR units are separated from each other by a short distance (less than 1 ft), fire propagation along the pallet row would not be expected

With the major fire contribution coming from the hydrocarbon fluid spill, the pallets contribution is very minor.

Wood pallets will require a radiant heat flux in excess of 15 kW/m2 in order to ignite.

A typical evaluation fire for the K-25 and K-27 Bldgs is 5270 kW over 32 ft2 (4’ by 8’ by 4’ combustible package). The radiant heat flux at the floor from this fire is 7 kW/m2 at 10 ft from the fire

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One more example from the K-25/K-27 FHA

Scenario: hydraulic fluid fire in foaming trailer unit The hydraulic system reservoirs contain approximately 34 gal of

hydraulic fluid (e.g., Mobile DTE 24 or 25 hydraulic fluids). The recommended operating temperature for the hydraulic system is

48C (120F) while the maximum operating temperature is 71C (160F). The Mobile DTE 24 fluid has a flash point of 220C (428F) and the

Mobile DTE 25 fluid has a flash point of 232°C (450F). A significant leak in the hydraulic system could result in a hydraulic

pool spill within the center compartment of the trailer. If the total 34 gal of the hydraulic fluid were to be spilled over the center compartment of the foam trailer, the pool depth would be approximately ¾ in.

If this spill pool could be ignited and sufficient air could be provided to the fire, this would result in an approximately 10 MW fire that would last just over 6.2 minutes.

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Example from WIPP FHA

Scenario: Diesel fuel fire from vehicle remote refueling

WIPP operating procedures only allow a 5‑gal portable container of diesel fuel to be transported to the out-of-fuel vehicle for refueling to provide a sufficient quantity to restart the vehicle and allow it to proceed to the underground refueling station to complete refueling.

Provides a possible fuel spill fire event of 5-gal of fuel at any location in the mined area.

A 5-gal diesel fire from a spill covering 20 ft2 can result in a 3.6 MW fire lasting about 3½ minutes after achieving full pool involvement.

Should the fire ignite the exposed vehicle, the fire size could be larger.

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And finally an example for an FHA for the West Valley Site (may not be published yet)

Scenario: Hydraulic device used for D&D of facility

The hydraulic reservoir size of the various hydraulically assisted devices is typically 40 gal or less in total capacity.

Highly protected industrial risk guidance such as from FM Global Data Sheet 7-98 would not require special fire protection measures (such as automatic sprinklers) unless several small systems closely located (i.e., within 20-ft) contained a total aggregate of 100 gal or more of combustible hydraulic fluid.

Even though the hydraulic fluid, if leaked, is not expected to become involved in a fire due to the minimal and low energy ignition sources normally present, a fire, should it occur, would involve no more than 40 gal of hydraulic fluid.

Should this fluid ignite over a 100-ft2 area (0.64-in. deep spill), the resultant fire would be limited to approximately 15.1 MW in size and last slightly more than 5 minutes.

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A fire of this size and type would be readily noticeable by operators but due to the short duration, the fire would be expected to self extinguish (i.e. run out of fuel) before operators could adequately respond with fire suppression actions.

Should this fire occur in one of the MPP cells, the substantial concrete

construction and heavy construction features that confine radiological areas would be expected to confine the fire such that no significant building damage or release of radiological material would result.

To help prevent events of this nature, the use of high fire point

hydraulic fluids are usually employed and as mitigative and preventative measures, open flame cutting, grinding and cutting wheel activities are conducted under hotwork controls with a posted fire watch

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Conclusions:

Fire modeling can help evaluated a fire scenarios and keep in bounds Several good fire models are available for no cost Validation of some of the models for certain fire parameters have been

published The model does not have to be too complex to be of value. Have yet to use CFAST except in the office FDS is fun but takes a lot of computer time, were working on

improvements Selection of the fire model to use depends on hove complex the fire

scenario is Have yet to exceed the ability of FDTs spreadsheets Prepared to go deeper Our philosophy is to keep everything as simple as possible

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Thank You

Fire Modeling Applications in FHA’s Gaines E. Bruce, P.E., SFPE WSMS-Mid America 105 Mitchell...

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Transcript of Fire Modeling Applications in FHA’s Gaines E. Bruce, P.E., SFPE WSMS-Mid America 105 Mitchell...