The SAFRAN tool

Safety Assessment in Predisposal Waste Management

IAEA 21-25 March 2011

Purpose of the tool

Implementation of methodologies for SA in pre-disposal waste management developed in the frame of the SADRWMS project. The tool should be helpful in:

• Describing predisposal radioactive waste management and decommissioning activities in a structured way,

• Conducting the safety assessment with clear documentation of the methodology, assumptions, input data and models,

• Establishing a traceable and transparent record of the safety basis for decisions on proposed waste management solutions,

• Demonstrating clear consideration of and compliance with national and international safety standards and recommendations

Areas of application

The tool is applicable to pre-disposal waste management activities:

• retrieval, treatment and storage of existing wastes;• treatment and storage of decommissioning wastes;• treatment and storage of institutional wastes (e.g.

sources);• treatment of liquid waste;• clearance of waste;• discharges.

Overview of SAFRAN Tool 4

Benefits of SAFRAN• Provides methodologies recommended by the IAEA and tools

that have been conciliated at international level.• Facilitates performing iterations of the Safety Asessment, for

example in case of upgrades of the facilities, if new waste streams appear, etc.

• Facilitates regulatory review by providing a transparent representation of all SA components.

• Several experts can work more effectively in the same Safety Case. The regulator can use the SAFRAN projects in independent safety assessments

• SAFRAN can be used for creating generic safety assessments• Possibility to exchange experience through sharing projects and

databases.

History of the development (1)

• The tool development started in April 2005In the frame of the IAEA project:

SADRWMS – Safety Assessment Driving Radioactive Management Solutions

• From April 2007 it was introduced in another IAEA project:

DeSa – Safety Assessment in Decommissioning

• From 2008 – Sponsoring from SSM (Sweden), NDA (UK) and IRSN (France)

History of the development (2)

• From April 2008 - development of a new User Interface and new Calculation Tool based on Ecolego.

• Development of website for downloading the tool.

• Development of first version of User Guide in Wiki language.

• Translation of the interface to Russian language.

AUGUST 2010 – RELEASE OF VERSION 1.0

• Testing by Studsvik AB

• Preparation of User Guide an Tutorials

• Improvements in Safety Assessment Module

Test Cases

• Development of specifications: Treatment plant in Vinca,

• IAEA training courses: Slovenia, Croatia, Moscow, Belarus, Chile and Cuba,

• Development of specifications for decommissioning: Decommissioning of a nuclear laboratory in the US.

• Waste Treatment Plant and Storage facility of the Leningrad Nuclear Power Plant,

• Treatment Plant in Studsvik – 2 iterations (Sweden),

• National waste treatment and storage facility in Thailand.

SAFRAN components

System descriptionSite features, waste producers,

waste streams

Regulatory Framework

Safety AssessmentNormal Operation,

Accidents

SAFREQ

SAFCALC DATABASE

Report

Report

System Description

For each configuration

• Site • Facilities

– Rooms» Areas (Storage or Processing)

Physical elements

Safety elements

• Waste Management Activities– Processes– Check for clearance

• Waste Producers– Primary Waste Components

» Waste Streams

Types of safety elements

• Site selection

• Safety functions

• Limits and conditions

• Mantainance requirements

• Operational procedures

• Emergency procedures

• Management systems

Can be linked to physical elements and assessments

Waste management activities

– Description– Output(s) from activities– Reduction factors– One and only one WMA can be assigned to an

area

Reduction factors

• Define how the activity changes the waste properties: Volume, mass and activity

Sorting of waste

Output Volume Massa Activity

Combustible 5 % 5 % 5 %

Non combustible 95 % 95 % 95 %

Check for clearance

• Possible to make comparisons of activity concentrations in the waste components against IAEA´s and user defined clearance criteria

• Clearance criteria are defined for unconditional clearance of solid materials and expressed in Bq/g

Processes

• A process is a sequence of WMAs which can be used in defition of Waste Streams (WS)

Waste Streams

• The definition of waste streams allows representing the fate of waste components through different steps of processing, storing and clearing wastes and allows to consider changes of waste properties in these steps.

SAFRAN components

System descriptionSite features, waste producers,

waste streams

Regulatory Framework

Safety AssessmentNormal operation,

accidents

SAFREQ

SAFCALC DATABASE

Report

Report

Regulatory Framework

• Regulatory requirements

• Criteria Normal operation and accidents.

Workers and members of the publicDose in Sv/y

• Several regulatory frameworks can be added to a project, for example IAEA and national and all can be used in a SA

SAFRAN components

System descriptionSite features, waste producers,

waste streams

Regulatory Framework

Safety AssessmentNormal operation,

accidents

SAFREQ

SAFCALC DATABASE

Report

Report

Safety Assessment types

• Normal operation and accidents

• Impact on workers and members of the public

• Impact inside and outside the facilities

Assessment context

• Link to one or more Regulatory Frameworks

• Purpose – select from a list or add own

• Scope – Define which facilites, rooms and areas will be included in the SA at at what level the assessment is carried out

• Approach

– PIEs will be defined or only PIE types will be used.

– Screening of Hazards will be done or not

– Compliance with Safety Requirements will be assessed or not?

Safety Assessment for Normal Operation

• Endpoints definition – several endpoints that can be optionally linked to one or more criteria

– Inside and Outside

– Dose (Sv/y) or Other

• Scenarios (Impacts in normal operation)

– Relevant or not relevant

– Bounded or not (currently practically not used)

– Quantitative or qualitative

– Inside or outside

– Radiological consequences

• Inside: Direct external exposure and exposure by inhalation or Other

• Outside: Releases to air, liquid discharges or Other

Assessment of impactsImpacts

Screening or Hazards

Exposure Assessment

Optional step calculations for standardized conservative exposure situations

calculations for specified endpoints and expecific exposure conditions

Impacts inside during normal operation external irradiation and inhalation

• Hazard quantification – External dose rates (Sv/h) and air concentrations (Bq/m3), taken from the System Description, are used to calculate the dose rate (Sv/h) from occupancy of the room. A Hazard Quotient (HQ) is calculated by dividing this dose rate by a Screening Dose Rate. The Screening Dose Rate is found in the Database – the user can define it´s own value.

• Exposure assessment – The dose rates (Sv/h) are used for calculation of annual doses (Sv/y) by multiplying by the exposure time. If the same endpoint is assigned to several scenarios, then for this endpoint SAFRAN will also calculate the sum of the doses from all scenarios.

Impacts outside during normal operation releases to air and liquid discharges

• Hazard quantification – Release rates to air (Bq/y) and liquid discharge rates (Bq/y), taken from the System Description, are used to calculate a Hazard Quotient (HQ) by dividing these by Screening Release Rate or Screening Discharge Rate. The Screening Release Rate and Screening Discharge Rate are found in the Database – the user can define it´s own value.

• Exposure assessment – The above Release rate (Bq/y) is used for calculation of annual doses (Sv/y) by multiplying by a Dose Conversion Factor (DCF). Values of the DCF are found in the Database.

Safety Assessment for Accidents• PIE types

– External natural

– External human induced

– Internal

• Endpoints definition – several endpoints that can be optionally linked to one or more criteria

– Inside and Outside

– Dose (Sv/y) or Other

• Scenarios and impacts

– PIEs

– Scenarios

– Impacts

Assessments for accidents

Impact 1

PIE Type

PIE 1 PIE n

Scenario 1 Scenario n

Impact n

Endpoint 1 Endpoint n

Ass Case 1

Ass Case n

Scenario m

Impact m

PIE properties• Relevant or not

• Probability (per year or during facility lifetime)

– Qualitative: Very Low, Low, Medium, High, Very High

– Quantitative: Probability of occuring at least once

Default scale of probabilities

QualitativeCategory

Probability during lifetime

Annual probability 1/y

Very High > 95 % > 3,0E-02

High 75-95 % 1,4E-02 - 3,0E-02

Medium 5-75 % 5,0E-04 - 1,4E-02

Low 0,1-5 % 1,0E-05 - 5,0E-04

Very Low < 0,1 % < 1,0E-05

Scenario properties

• Relevant or not

• The probability may or not be the same as the probability of the linked PIE

• Several scenarios can be linked to the same PIE, but a scenario has only one PIE

• A scenario may have several impacts and several scenarios can be linked with the same impact

Properties of impacts from accidents

• Relevant or not relevant

• Bounded or not (currently practically not used)

• Quantitative or qualitative

• Inside or outside

• Radiological consequences

– Inside: Releases to air, increased external exposure and Other

– Outside: Releases to air, liquid discharges or Other

• If the same endpoint is assigned to several impacys of the same scenario, then for this endpoint SAFRAN will also calculate the sum of the doses from all impacts.

Potentially Affected Inventory (PAI)

• Also known as Material At Risk

• Is the radionuclide inventory or amount, in Bq, that can be affected during an accident.

Examples– The PAI for an accident consisting of dropping

a waste package equals the total activity in the package.

– The PAI for an accident during a processing activity equals the activity involved in one instance of the activity

Calculation of PAI

• For Storage Areas the PAI is the total activity present in the Area, i.e. the summa over all stored Waste Components.

• For Processing Areas the PAI is the Capacity of the Processing Activity (m3) multiplyied by the radionuclide concentration in the waste. For each processing activity SAFRAN calculates two PAI values, using the concentrations in the waste before and after the activity. The user has to choose between these.

• In the PAI calculation for an Area, all Waste Streams passing through this Area are considered.

• In the PAI calculation for a Room all areas in this Room are considered.

• In the PAI calculation for a Facility all Rooms in this Facility are considered.

Impacts inside from accidentsincreased external irradiation

• Hazard quantification – Dose rates (Sv/h) at one meter from a point source with an inventory (Bq) equal to the Potentially Affected Inventory (PAI) are calculated. A Hazard Quotient (HQ) is calculated by dividing this dose rate by a Screening Dose Rate. The Screening Dose Rate is found in the Database – the user can define it´s own value.

• Exposure assessment – The PAI are used to calculate external doses using dosimetry models, available in SAFCALC for different geometries. The values of distance from the source and exposure time, entered by the user, are taken into account, as well as shielding effects (optional).

Impacts inside from accidentsreleases to air

• Hazard quantification – The PAI is multiplied by the Release Fraction to obtain the Release to air. A Hazard Quotient (HQ) is calculated by dividing this Release by a Screening Release. The Screening Release is found in the Database – the user can define it´s own value.

• Exposure assessment – The Release (Bq) are used to estimate doses by applying a Dispersion Factor (h/m3), which depends on the values of distance from the source, exposure time and room volume entered by the user. The Dispersion Factor is found in the Database – the user can define it´s own values.

Release Fractions

• Release Fraction (RF) is the fraction of the Potential Affected Inventory that is released to air.

• The RF depends on the Waste form, the radionuclide and the type of effect of the accident.

• Values of RF are given in the Database.

• It is assumed that RF correspond to respirable fractions.

Impacts outside from accidentsreleases to air

• Hazard quantification – The Release outside re obtained by multiplying the Release inside by factor that accounts for reduction of releases by filtration. A Hazard Quotient (HQ) is calculated by dividing this Release by a Screening Release. The Screening Release is found in the Database – the user can define it´s own value.

• Exposure assessment – Doses are calculated by multiplying the Release (Bq) by a Dose Conversion Factor (Sv/Bq). The Dose Conversion Factor values are found in the Database – the user can define it´s own values.

SAFRAN components

System descriptionSite features, waste producers,

waste streams

Regulatory Framework

Safety AssessmentNormal operation,

accidents

SAFREQ

SAFCALC DATABASE

Report

Report

Models available in SAFCALC

• IAEA SR-19 models: screening calculations for routine releases to the atmosphere, lakes, rivers, estuarines and coastal areas.

• Model for accidental releases to the atmosphere.

• Model for accidental releases inside a room.

• Simple dosimetry models: point source, disc, cylinder, cube (with and without shielding)

Uncertainty analysis

• Probabilistic simulations using Monte Carlo random sampling and Latin Hypercube sampling

• Sensititivy analyses using regressions, correlations and variance based methods.

SAFRAN components

System descriptionSite features, waste producers,

waste streams

Regulatory Framework

Safety AssessmentNormal operation,

accidents

SAFREQ

SAFCALC DATABASE

Report

Report

Database

• Radionuclide halv lifes

• Clearance levels

• Gamma constants

• Screening dose rates for Normal and accidental situations

• Screening release rates for Normal operation

• Screening releases for accidental situations

• Release Fractions

• Dispersion factors

• Dose Conversion Factors for Normal and accidental situations