The Structure and Application of High Level Safety Goals

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1 Multinational Design Evaluation Programme (MDEP) The Structure and Application of High Level Safety Goals Geoff Vaughan Safety Goals Subcommittee Chair

2 Background - 1 MDEP Multinational Design Evaluation Programme An initiative taken by national safety authorities to leverage their resources and knowledge for new reactor design reviews Members are: Canada, China, Finland, France, Japan, Korea, Russia, South Africa, USA, UK plus IAEA Aims include: To facilitate harmonisation of regulatory requirements To facilitate licensing of future reactors, including Generation IV 2

3 Background - 2 To achieve harmonisation there needs to be a convergence on the safety goals which must be met To regulate future reactors needs the development of consistent safety goals for different technologies This means there needs to be a comparison and understanding of the bases for the safety goals in each MDEP country and how they are expressed 3

4 Definition of Safety Goals What is meant by safety goals in this work? All Health and Safety requirements covering radiation risks to workers, the public and the environment, whether due to normal operational exposures and discharges or accidental occurrences cf Basic Safety Objective in IAEA Safety Fundamentals 4

5 What s New? - 1 * Increasing interest in Risk-informed Decision Making combining probabilistic and deterministic considerations. * Many surveys have been done which have listed low level goals eg specific temperatures in reactor vessels of a specific type, or frequencies of specific events. * Differences arise due to different principles and assumptions in derivation and the detailed design considerations. * But without understanding these factors it is not possible to determine if the goals are consistent and coherent. 5

6 What s New? - 2 We need to go back to basis of the safety goals. The approach we have taken is to: # start with the high level safety goals ie the requirements to protect people and the environment, # determine a structure for the safety goals that can be used for all types of nuclear technology, # develop a method to derive lower tier safety goals so they consistent for different technologies and are clearly related to the higher tier goals. 6

7 MDEP Subcommittee The MDEP Steering Technical Committee (STC) set up a subcommittee to pursue this work with the remit to initiate discussions with other bodies and recommend a way forward so that MDEP could complement their work. The subcommittee remit did not cover the development of a set of detailed safety goals. Participants: Canada, Finland, Japan, South Africa UK, USA, and IAEA 7

8 Work Undertaken Related activities Identification and interaction with other groups Survey of subcommittee members approaches and definition of high level safety goals Determination of commonalities and a proposed coherent framework for all technologies Procedure for developing lower tier safety goals in a consistent way Application to specific reactor types ie proof of usefulness Development of a report to MDEP ( in draft) Drafting of MDEF Position Papers on Integrated Riskinformed Decision-Making and Safety Goals (awaiting approval from MDEP) 8

9 Interactions with Other Groups IAEA/INSAG IAEA were represented on subcommittee; two members on drafting group for INSAG-25 on Integrated Risk-informed Decision Making CSNI/WGRisk members of WGRisk invited to subcommittee meeting to discuss work on probabilistic risks GIF/Reactor Safety WG Representative of RSWG attended subcommittee meeting to discuss their work on future reactors WENRA/Reactor Harmonisation WG chairman of RHWG attended two subcommittee meetings to discuss report on New Reactors; one member of subcommittee is member of RHWG 9

10 Other Groups: INSAG-25-1 INSAG -25 International Nuclear Safety Group group of experts providing authoritative on nuclear safety to IAEA INSAG 25 Risk-Informed Decision Making Considers Key elements that contribute to a risk-informed decision Uses of RiDM Managing the process Training Documentation But does not attempt to set criteria (about to be published) 10

11 Other Groups: INSAG-25-2 INSAG -25 Key Elements of RiDM 11

12 Other Groups: WENRA WENRA Western European Nuclear Regulators Association Reactor Harmonisation Working Group Draft of Safety Objectives for New Power Reactors - December 2009 O1. Normal operation, abnormal events and prevention of accidents O2. Accidents without core melt O3. Accidents with core melt O4. Independence between all levels of defence-in-depth O5. Safety and security interfaces O6. Radiation protection and waste management O7. Management of safety The subcommittee sees some useful synergies between these objectives and the approach that it is pursuing 12

13 Survey of High Level Safety Goals Survey Most countries require that NPP should add only insignificantly to risks to population: expressed in terms of deaths or cancer incidence. These cover workers, discharges to environment and accidents. Many goals relate to effects on individuals but all countries also recognise effects are wider such as use of land or food production. ~~~ The IAEA Basic safety Standard is the basis for occupational and public dose limits during normal operation. For new reactors, all countries propose offsite releases should be reduced to low level or practically eliminated. Major damage state frequency targets reduced by about an order of magnitude (WGRisk survey). 13

14 Defence-in-Depth -1 Din D All countries use a form of Defence-in Depth concept in making decisions on nuclear safety INSAG-12 provides good background Enshrined in several IAEA Safety Standards from Safety Fundamentals down Given wide usage and that philosophy has resulted in excellent safety record, subcommittee determined that a framework based on Defence-in-Depth should be used to define the structure of lower tier safety goals 14

15 Defence-in-Depth -2 Din D Advantages: Based on consensus IAEA Safety Standards Well-known in nuclear industry Simple, straightforward philosophy Enables clarity of combining deterministic and probabilistic goals Develops the INSAG-25 RiDM approach Allows for a coherent and consistent development of lower tier goals from high level goals 15

16 The Structure and Application of High Level Safety Goals (SAHLSG) - 1 The aim of the Subcommittee is to consider the framework within which potential goals can be included and be agreed upon as a move towards harmonisation. A draft paper reviews the high-level goals used in some MDEP countries and draws broad conclusions. We hope to include data from more [MDEP] countries in future drafts. From the survey results and other considerations, the Subcommittee has developed a set of possible safety goals and proposed a method of applying them within an extended DiD structure. MDEP are currently considering these proposals. 16

17 The Structure and Application of High Level Safety Goals (SAHLSG) - 2 The paper indicates the broad framework of how the safety goals can be integrated, effectively giving more detail on the INSAG-25 approach. It also considers how it should be applied when deriving suitable safety goals for application to NPP. We intend to develop this approach and hope to have further discussions with other organisations, IAEA and WENRA in particular. We expect to publish on the NEA/MDEP website in due course. 17

18 The Structure and Application of High Level Safety Goals (SAHLSG) - 3 Extended DiD Structure It is proposed that: the DID structure is extended to integrate the elements of safety to protect health and safety during normal operation and accident conditions for the whole plant lifecycle. this structure should comprise a hierarchy: a top level safety goal, a set of high level safety goals to meet the top level safety goal, and lower level goals/targets, derived from the higher level for application to design and operation. Importantly, this structure is technology-neutral 18

19 The Structure and Application of High Level Safety Goals (SAHLSG) - 4 Extended DiD Structure Top Level Safety Goal High Level Safety Goals DiD and Risk Goals Lower level Safety Goals and Targets (Deterministic and Probabilistic) Technology Specific Targets 19

20 The Structure and Application of High Level Safety Goals (SAHLSG) - 5 Proposed high level safety goals Top-level Safety Goal Provide a level of safety such that the risks to people and environment from the whole lifecycle of a nuclear power plant is only a small fraction of the risks from other hazards to which these are otherwise subjected. 20

21 The Structure and Application of High Level Safety Goals (SAHLSG) - 6 Proposed high level safety goals High level DID goals 1. Occupational and public dose limits during normal operation, should conform to the IAEA Basic Safety Standard, which is derived largely from the ICRP recommendations. 2. Prevention should be the focus by designing for fault tolerance through using good engineering principles. 3. Within the design basis, there should be no offsite effects and no significant onsite doses for workers, as far as practical. 4. Large offsite releases due to accidents, should be as infrequent as practical. 5. Any offsite releases that could occur should only require limited offsite emergency response. 21

22 The Structure and Application of High Level Safety Goals (SAHLSG) - 7 Proposed high level safety goals Extended DID high level goals I. Integration of safety and security measures should ensure II. III. IV. that neither compromises the other. Siting factors, in addition to being considered within the design should also be taken into account in considering emergency arrangements. Where improving safety is, or over the lifetime of the plant becomes reasonably practicable, then this improvement should be implemented. Where an exposure occurs, the likelihood should decrease as the potential magnitude increases. V. Independence of the barriers and systems that form the protection at the different DID levels is a fundamental aspect of the safety concept, which should be ensured and enhanced in new and future reactors, as far as practicable. VI. VII. Consideration of the management of radioactive waste during the design, operation and decommissioning phases, should be such that the generation of waste is minimized. Arrangements to ensure effective management of safety should be made at all lifecycle phases of a reactor. 22

23 The Structure and Application of High Level Safety Goals (SAHLSG) - 8 Extended DiD Structure Safety Goals are generally qualitative, or define upper limits, setting out what has to be achieved Targets are usually quantitative and developed from the Safety Goals, setting out the measure of achievement Further development to technology specific targets should therefore be consistent and coherent Goals should be achieved Targets: *** failure to meet must be robustly justified, failure to do better must be explained. 23

24 Position Papers The Subcommittee has always viewed itself as having a limited lifetime and it s aim is to provide a baseline for MDEP to use in future work and discussions. With the agreement and co-operation of the MDEP STC, we are developing Position Papers on: Integrated Risk-informed Decision-Making, and Safety Goals. Drafts will be considered by the MDEP STC in October. These Position Papers will be the basis for further work on these topics within the MDEP system. 24

25 Position Paper on Integrated Riskinformed Decision-Making Three elements: 1. Strong support for the use of integrated decision-making for design evaluation and operational safety; 2. Endorsement of the approaches set out in INSAG 25; 3. Recognition of the need to develop the process and determine suitable safety goals. 25

26 Position Paper on Safety Goals Three elements: 1. An expectation that higher levels of safety will be achieved in the design and operation of new reactors. 2. Support for the structure of safety goals and targets, as set out, for consideration of its members, IAEA and other organisations in moving towards international harmonisation of regulatory requirements; 3. Recognition of the need to develop the process, and for continued interactions with other organisations, to further harmonise regulatory requirements. 26

27 Future Programme Autumn 2011 Finalise Position Papers on Safety Goals and Use of IRiDM Spring 2011 Finalise MDEP Structure and Application of High Level Safety Goals Paper Publication through the MDEP website is envisaged April 2011 Contribute, based on Report and Position Papers to initial meeting of IAEA group to develop a Safety Guide on Safety Goals It is hoped that during the further work discussions will be held with other interested organisations but this is dependent on the MDEP STC and Policy Group agreement. 27

28 Some final, personal words Design Safety Goals do not make a reactor safe: there are uncertainties in the analysis, construction may not meet intentions and good designs can operated badly etc Safety Goals must be considered in both design and operational contexts. Whilst hard numbers can be seductive numbers should guide not decide! There is no single attribute that can be used to say an NPP is safe: there has to be balanced view covering all the hazards and risks and the people who can be harmed judgement is necessary, there is no algorithm! RiDM, building on a proper balanced view of these factors, using wellchosen goals (which may not be numerical), can provide a coherent and consistent decision making process, that be used for all technologies. 28