iaea workshop on the application of the iaea methodology and safety assessment framework (safran)...
TRANSCRIPT
IAEA
Workshop on the Application of the IAEA Methodology and Safety Assessment Framework (SAFRAN) Tool for the Safety Case and Safety Assessment for Predisposal Management of Disused Sealed Radioactive Sources (DSRS)
Athens, Greece, 23-27 June 2014
Earl FordhamWashington Department of Health, USA
Definition, Role and Documentationof the Safety Case: Quick Review
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Outline of the Presentation
• Overview of Safety Case• Specific issues
• Evolution of the safety case;• Graded approach;• Defense in depth;• Reliability;• Expected lifetime of the facility;• Long term storage;
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Overview: Purpose of safety case
• Demonstrate that all planned activities can be carried out in a safe mannerThe SC concept will be of particular importance for
large predisposal waste management facilities such as national centres for the processing and storage of radioactive waste.
• Provide guidance for the design, engineering and planning of operations to ensure safety
• Input to regulatory process, including evidence of compliance and arguments for confidence building
International Course on Management of Waste, Clausthal-Zellerfeld, Germany, 6-15 October 2010 3
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Objectives and Roles of SC and SA (GSG-3)
Integrating scientific and other information
Demonstrating safety (incl. uncertainties)
Demonstrating compatibilities with next
waste management steps (e.g. disposal)
Aiding decision making on the
authorisation/ licensing of the facilities
Other information and arguments that
support continued development, use or
eventual decommissioning of the facility
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Overview: What is a Safety Case?
The collection of arguments and evidence, including the outcome of safety assessment, in support of the safety of a facility or activity (GSR-5, GSG-3)
The basis for the safety considerations in respect of siting and locating facilities, construction, operation and decommissioning of the facility, including the justification for changes
The basis for interaction and dialogue between the operating organization and the regulatory body
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• Normally includes the findings of a safety assessment, together with:• Consideration of the confidence level in these
findings, • A written statement assessing the adequacy of the
assessment work for the decisions to be taken, and • The need for any further work to reduce uncertainty.
• Components of the Safety Case can be found in GSG-3
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Overview: What’s in the Safety Case?
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Role of the Safety Case in
Ensuring Long Term Safety• Interdependencies:
• Transfer of Ownership, Responsibilities, Information • Long Term Strategies for management of DS, RW and SF• Safety implications of delayed disposal• Informing decision making (e.g., management of legacy
sites, considering new/expanded nuclear programmes)• Demonstration of Safety
• Licensing and authorization • Interactions w Stakeholders• Engineering Barriers• Management Systems• Monitoring and Inspections
Waste and materials
Exempt wasteand materials
Radioactive material (for reuse/recycle)
Pretreatment
Treatment
Conditioning
Disposal 7
STORAGE
TRANSPORT
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Development and content of SC and SA
Some countries do not use the term SC in a formal way, but the approaches and processes to demonstrate safety similar
The operator shall prepare a safety case and a supporting safety assessment. Do we have any regulator/operators here today?
In the event of a step by step site development or in the event of the modification of the facility or activity, the SC and its supporting SA shall be reviewed and updated as necessary. Any one going beyond storage?
Regulatory body is responsible to derive and document in a clear and unambiguous manner the criteria on which the regulatory decision making process is based
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• SPECIFIC ISSUES (step 6):
- Evolution of the safety case- Graded approach- Defense in depth- Reliability- Expected lifetime of the facility- Long term storage
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Introduction
During facility lifecycle, the safety case will evolve in five main stages:
• Concept and siting;• Design;• Construction and commissioning;• Operation and modifications;• Shutdown and decommissioning.
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Concept and siting (cont.)
The output of the safety case at this stage of development is justification that the facility (or activity) is safe to be built.
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Design
• During the design development and construction, the safety case will be further developed to provide a mature assessment of the engineering and the impact of the facility or activity;
• The safety case should demonstrate that:Likelihood of a component of the system failing is low, In the event of degradation, the loss of a safety function
of one component does not jeopardize the safety of the whole system (defense in depth)
• Can be safely constructed and operated.
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Construction and commissioning (cont.)
• The safety case at this stage should demonstrate that the as constructed facility meets the safety requirements specified in the final design.
• This should include the impact of any modifications to the design, which have been implemented during the construction stage.
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Operation
• Must investigate and recertify any significant differences between the actual and predicted performance of the facility discovered during commissioning testing.
• To recertify facility, perform PSR periodically, when plant status or management changes, or after regulatory changes.
• SC should document procedural changes for safety, record tracking systems, and sufficient expertise exists for operations and other interdependencies, as needed.
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Operation (cont.)
The aim of the operational safety case is to justify that the facility can be operated safely for a specific period and can then be safely decommissioned.
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• SPECIFIC ISSUES:- Evolution of the safety case- Graded approach- Defense in depth- Reliability- Expected lifetime of the facility- Long term storage
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Graded approach
• The scope/level of detail of the safety assessment for a particular facility shall be consistent with the magnitude of the possible radiation risks from the facility (e.g., simple site; simple assessment),
• Expect greater efforts will be needed in developing SC & SA for a large treatment facility than for a small low-level waste storage facility.
• Learn the degree of detail required for a SA by first undertaking relatively simple SA’s that provide an indication of the potential levels of risk.
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Graded approach: Criteria (cont.)
• Various criteria may be used in determining the level of understanding that should be expected for a particular facility;
• Criteria may include:Safety significance (most important),Complexity,Maturity of plant operators/operations.
• Facility performance viewed in terms of:Releases from normal operation, Potential consequences of anticipated operational
occurrences and reasonably foreseeable accidents, Potential significance of low probability events with
potentially high consequences.
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• SPECIFIC ISSUES:- Evolution of the safety case- Graded approach- Defense in depth- Reliability- Expected lifetime of the facility- Long term storage
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Defense in depth: Concept
• The defense in depth concept is centered on several levels of protection including successive barriers and other safety functions preventing the release of radioactive material to the environment and minimizing exposures;
• The concept includes:Maintaining the effectiveness of the barriers by averting
damage to the facility and to the barriers themselves;Further measures to protect the public and the environment
in case of unexpected malfunction or degradation of barriers (up to & including infrequent design basis events).
• Example: combine passive engineered barriers (preferred) with approved procedures.
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Scope of the safety case for predisposal RW
• Relevant facilities / activities: Processing of radioactive waste Clearance and Discharges Storage facilities Transport Intervention situations (e.g. old storage facilities)
• All types of wastes low level to high level waste disused sealed sources NORM
International Course on Management of Waste, Clausthal-Zellerfeld, Germany, 6-15 October 2010 21
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Suggested SC Documentation Format
• No universal, but suggested format (Section 7):• Executive Summary,• Introduction & Context (e.g., why) for SC,• Strategy for Safety (selection, location, barriers),• Safety Assessment, and• Synthesis and Conclusions.
• Minimum Safety Case is just the SA with operating limits and conditions.
• Actual format is subject to your audience.
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Safety Case contents
The safety case (SC) shall: Include a description of how all the safety aspects of the
site, the design, operation, shutdown and decommissioning of the facility, and the managerial controls satisfy the regulatory requirements,
Demonstrate the level of protection provided and shall provide assurance to the regulatory body that safety requirements will be met,
Include arguments justifying the approaches taken in the safety case on the basis of information that is traceable, and
Document the arguments at a level of detail and to a quality sufficient to demonstrate safety.
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Safety Case contents con‘t
Discussion of the various waste types and the rationale for the chosen/proposed waste management options,
Areas and the processes used at the site,
Managerial structure and regulatory controls over the facilities,
Plans regarding the development, operation and shutdown and decommissioning of the facilities,
Safety assessment (SA),
Other information and arguments supporting the development and use of a facility.
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