Transcript The SADRWMS tool - International Atomic Energy Agency

SAFRAN
Upgraded to support the
implementation of the
Borehole Disposal Concept
Rodolfo Avila, Facilia AB
Outline
• Description of SAFRAN
• Adaptation to support the implementation of the
BDC.
• Generic Operational Safety Assessment
(GOSA)
What is SAFRAN
• SAFRAN is a software package for safety
assessment in pre-disposal waste
management.
• It implements the methodology developed
within the IAEA project SADRWMS (20052010)
SADRWMS
methodology
Purpose,
Regulations, Standards …
Assessment Context
Engineering design,
Safety measures,
Other relevant information
(management systems, operational
experience, site data …)
Description of Facility or Activity
and the Waste
Development and Justification of Scenarios
Identification of Hazards
Provides detailed
guidelines for safety
assessment.
PIE lists, Expert judgements
Identification of Scenarios
Screening of Hazards
Formulation of Models and
Identification of Data Needs
Models and computer codes;
Generic / site specific data
Performance of Calculations
Based on the IAEA
safety guide DS284: The
Safety Case and Safety
Assessment for
Predisposal Management
of Radioactive Waste
Evaluation of Results
Analysis of Safety Measures
Analysis of Engineering
Comparison with Assessment
Criteria
Yes
Yes
Accept
Adequate?
No
Independent
verification
No
Adequate?
Review
and
modify
The SADRWMS methodology
• Provides detailed advice for each step of the
Safety Assessment
• Describes the different types of
assessments that might be required
• Provides methods for Hazard identification
and screening
• Provides methods for performing qualitative
and quantitative assessments for different
scenarios
Disposal Borehole Design &
Construction
Borehole
Diameter – 260mm
Length – variable
Casing
Diameter – 160mm
Length - variable
Disposal Container
Diameter – 115mm
Length – 250mm
Capsule
Diameter - 21/48mm
Length – 110/121mm
Disposal container (with concrete insert) and container lid. Bottom row:
sealed capsules in two sizes.
Emplacement and Borehole Closure
Pre-disposal Activities
Construction of a borehole using
percussion drilling
SAFRAN components
SAFREQ
Report
System description
Site features, waste
producers, waste streams
Safety Assessment
Regulatory
Framework
Normal Operation,
Accidents
SAFCALC
DATABASE
Report
System Description
For each configuration
• Site
• Facilities
– Rooms
» Areas (Storage or Processing)
Safety elements
• Waste Management Activities
– Processes
– Check for clearance
• Waste Producers
– Primary Waste Components
» Waste Streams
Safety elements
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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
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Description
Output(s) from activities
Reduction factors
One and only one WMA can be assigned
to an area
A process is a sequence of WMAs which can
be used in defition of Waste Streams (WS)
Waste Streams
• Waste streams represent the fate of waste
components through different steps of
processing, storing and clearing of wastes
• Accounting for changes in waste properties
by waste management activities at each
step.
Additions for BDC
• The user can define that one or more
boreholes will be considered at a Site
• A library of safety elements of relevance for
BOSS will be added
• A library of pre-disposal waste management
activities relevant for BOSS
• A library of processes
Additions for BDC
• A library of sources
• SIMBOD – tool for management of the
Borehole Disposal process
• Typical waste streams – resulting from
application of Typical Processes to different
Types of Sources
Sources – Conditioned - Packaged
SAFRAN components
SAFREQ
Report
System description
Site features, waste
producers, waste streams
Safety Assessment
Regulatory
Framework
Normal operation,
accidents
SAFCALC
DATABASE
Report
Assessment types
• For normal operation and accidents.
• Doses to workers and members of the
public.
• Radiological impacts indoors and outdoors.
Graded approach to the assessments
Impacts
Screening or
Hazards
Dose
Assessment
Calculations of Hazard
Quotients (HQ) for
standardized conservative
exposure situations
calculations for specified
endpoints and expecific
exposure conditions
Assessments for accidents
PIE Type
PIE 1
Scenario 1
Scenario n
Impact 1
Impact n
Endpoint 1
Endpoint n
Ass Case 1
Ass Case n
PIE n
Scenario m
Impact m
Screening of hazards
Example of Probability-Consequence plots
HQ/Prob
Very
Low
Low
Medium
<0.1
Very
High
SC3
0.1- 1
SC4
1-10
SC2
10-100
>100
High
SC1
Additions for BDC
• Update of the PIE database
• Library of typical scenarios
• Library of generic safety assessments
SAFRAN components
SAFREQ
Report
System description
Site features, waste
producers, waste streams
Safety Assessment
Regulatory
Framework
Normal operation,
accidents
SAFCALC
DATABASE
Report
Models available in SAFCALC
• IAEA SR-19 models: screening models 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)
SAFRAN components
SAFREQ
Report
System description
Site features, waste
producers, waste streams
Safety Assessment
Regulatory
Framework
Normal operation,
accidents
SAFCALC
DATABASE
Report
Database
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Radionuclide half lives.
Clearance levels.
Gamma constants – dose rates at 1 m from a point source.
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.
Additions for BOSS
• Models and calculation methods used in Generic
Operational Safety Assessment (GOSA).
• Parameter values required for GOSA.
SAFRAN components
SPECIALIZED LIBRARIES FOR BOSS
SAFREQ
Report
System description
Site features, waste
producers, waste streams
Safety Assessment
Regulatory
Framework
Normal operation,
accidents
SAFCALC
DATABASE
Report
SAFREQ
• Tool for assistance in developing the safety
case by assessing compliance with Safety
Requirements and Safety Guidelines.
Additions for BOSS
• Going from a prototype to a Released
version
• Specific guidelines for safety case of BDC
GENERIC OPERATIONAL SAFETY
ASSESSMENT (GOSA)
Assessment Context
• The assessment context of the GOSA
should be consistent with the generic safety
assessment (GSA) for borehole disposal
(IAEA Safety Series Report: Generic PostClosure Safety Assessment for Borehole
Disposal of Disused Sealed Sources)
Purpose
• The purpose of the GOSA is to demonstrate that
the proposed pre-disposal waste management
activities are done in a safe manner, as required
by the regulatory framework. The safety of
operators (workers) and members of the public will
be assessed, both for normal operations and for
potential accidental situations.
Scope
• The starting point for the GOSA is that the Disused Sealed
Sources (DSSs) have arrived at the site and a decision has
been taken to “dispose” the DSS by borehole disposal
• Activities of the original producer [e.g. hospital] and
transport to site are beyond the scope of the current
project).
• Other disposal options (e.g. disposal in a near-surface or
deep facility) and management options (long-term storage)
are beyond the scope of this GOSA.
Inventory to be considered
• The inventory (Bq) and number of sources to be assessed
in the GOSA need to be representative of what is found in
practice in different countries.
• An initial proposal is to consider two cases: a country
(Ghana being an example) with a low to medium inventory
of relatively low level activity sources that do not require the
use of hot cells, and a country (South Africa being an
example) with a medium to large inventory which includes
high activity sources that will require the use of hot cells.
• Different initial states of the sources should be considered,
including sources in the original devices, in a transport
package, in the working container, and conditioned in
cement.
Regulatory Framework
• IAEA Safety Standards will be used as the basis
for the regulatory framework.
• This will include normal operation and accidental
situations, taking into account dose constraints as
well as dose limits.
• One issue currently under evaluation is whether to
include assessment of doses to the eye,
extremities, etc., in addition to whole body doses.
IAEA databases,
SIMBOD, etc
Inventory of
sources
Classification
of sources
Sources for Decay
Store
Sources for
Disposal
Other Disposal
Options
Sources for
BDC
Screening on
total
inventory
Use SAFCALC to obtain
operational activity
limits for capsules
WMA, etc
Number of
capsules required
for one borehole
Allocation of
Sources to
capsules
Several Boreholes
might be required
Temporary Storage at
Site
Prepare for Introduction
into Cell
Lift original Source Shield
into Cell
Close Cell
Remove Source and
Characterise
Encapsulation and
Testing
Condition into Disposal
Container
Lower into Borehole
Transfer Container to
Transfer Cask
Borehole Backfilling
Lower into Borehole
Borehole Backfilling
Typical activities and their duration
Operational activities
Duration
(Minutes)
1) Prepare for Introduction into hot cell
15
2) Lift Original Source Shield into the hot cell
5
3) Close the hot cell
20
4) Remove the source
60
5) Characterise the source
20
6) Encapsulation and test of the capsule
20
7) Place capsule in disposal container and NDT
20
8) Transfer disposal container to the transfer cask
10
9) Disengage and prepare the transport cask for
transport
15
10) Emplacement of the disposal container in borehole
15
11) Backfilling of the borehole
15
Examples of accidental scenarios (hot cell)
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The situation where the operation team is unaware that the source has an
activity greater than the value for what the facility was designed for and the
team proceeds with standard operations.
Error during the determination of the density of the shielding material (sand) in
the hot cell and the operation proceeds with a sand density below design
requirements.
Situation with the ZnBr2 window density below design requirements being used
by the operation team.
Source is dropped after being removed from the original source shield.
The source is found to be leaking when removed from the original source shield
inside the hot cell. (Could have been damaged during removal).
The manipulators malfunction whilst the source is inside the hot cell.
The biological shield is damaged while bringing in the original source shield.
Power outage in the hot cell.
Lights are not operational in the hot cell.