Review and Assessment of Engineering Factors

Transcription

1 Review and Assessment of Engineering Factors 2013

2 Learning Objectives After going through this presentation the participants are expected to be familiar with: Engineering factors as follows; Defense in depth (Multiple Barriers) Redundancy Diversity Radiation protection, etc.

3 References 1. Safety Assessment for Facilities and Activities, GSR Part 4 2. Review and Assessment of Nuclear Facilities by the Regulatory Body, GS-G Safety of Nuclear Power Plants: Design, SSR- 2/1 4. Establishing the Safety Infrastructure for a Nuclear Power Programme, SSG-16

4 Contents 1. IAEA Standards 2. Safety Assessment Safety Assessment for Facilities and Activities, GSR Part 4 Review and Assessment of Nuclear Facilities by the Regulatory Body, GS-G-1.2 Safety of Nuclear Power Plants: Design, SSR-2/1 3. Summary

5 1. IAEA Standards SSG-16 Actions 34, 38, 84, 97, 115, 120, 129, 144, 164, 182, 183, 188 GSR Part 4 Requirements 9, 10, 13 GS-G-1.2 Verification of the Safety Analysis 3.41 SSR-2/1 Requirements 22, 25, 30

6 2. Safety Assessment Safety Assessment Deterministic Safety Analysis (DSA) Predicts the response to pos tulated events with predeter mined assumptions; checks fulfilment of acceptance crite ria Safety Analysis Two complementary methods Probabilistic Safety Analysis (PSA) Combines the likelihood of ini tiating events, potential scen arios and their consequences into estimation of CFD, sourc e term or overall risk Assessment of engineering factors important to safety Proven engineering practices Defense in depth Radiation protection Safety classification Protection against internal and external hazards Combination of loads Selection of materials Single failure criterion Redundancy, diversity Equipment qualification Ageing Man-machine interface, etc.

7 2. Safety Assessment GSR Part 4 Safety Assessment for Facilities and Activities (2009)

8 GSR Part 4 Requirement 10: Assessment of engineering aspects It shall be determined in the safety assessment whether a facility or activity uses, to the extent practicable, structures, systems and components of robust and proven design. Proven engineering practices Defense in depth Radiation protection Safety classification, etc.

9 GSR Part 4 Proven engineering practices 4.29.Where innovative improvements beyond current practices have been incorporated into the design, it has to be determined in the safety assessment whether compliance with the safety requirements has been demonstrated by an appropriate programme of research, analysis and testing complemented by a subsequent programme of monitoring during operation.

10 GSR Part 4 Proven engineering practices For example, accident analysis computer code, how do we show the V&V of the code? Separate effect test Critical flow test, Integrate effect test LSTF, ATLAS, etc.

11 GSR Part 4 Defense in Depth, Multiple Barriers, Redundancy, Diversity The design principles applied will depend on the type of facility but could give rise to requirements to incorporate defence in depth, multiple barriers to the release of radioactive material, and safety margins, and to provide redundancy, diversity and equipment qualification in the design of safety systems.

12 GSR Part 4 Defense in Depth, Multiple Barriers Requirement 13: Assessment of defence in depth It shall be determined in the assessment of defence in depth whether adequate provisions have been made at each of the levels of defence in depth.

13 GSR Part 4 To determine whether adequate provisions have been made to ensure that the person responsible for the facility can: address deviations from normal operation; detect and terminate safety related deviations from normal operation; control accidents within the design limits; specify measures to mitigate the consequences of accidents that exceed design limits; mitigate radiation risks associated with possible releases of radioactive material.

14 GSR Part 4 To identify the necessary layers of protection, including physical barriers to confine radioactive material, and the necessary supporting administrative controls for achieving defence in depth. To determine whether there are adequate safety margins in the design and operation of the facility such that there is a wide margin to failure of any SSCs for any operational conditions.

15 GSR Part 4 To determine whether acceptance criteria for each aspect of the safety analysis are such that an adequate safety margin is ensured.

16 GSR Part 4 Defense in Depth, Multiple Barriers

17 GSR Part 4 (Defense in Depth) Objectives Accident Prevention: protection of the barriers by averting damage to the plant and to the barriers themselves Accident Mitigation: further measures to protect the public and the environment from harm in case these barriers are not fully effective Assumptions There will be errors in design Equipment will occasionally fail People will occasionally make mistakes

18 GSR Part 4 (Defense in Depth) Negative Reactivity Feedback + Reactor Control System Inherent Safety Precaution + Reactor Protection System + Engineered Safety Features + Severe Accident Precaution/Coping Prevention Mitigation Beyond DBA Event Frequency Core Damage Frequency

19 GSR Part 4 (Defense in Depth) Level 1 Level 2 Level 3 Level 4 Level 5 Objective Prevention of abnormal operation and failures Control of abnormal operation and detection of failures Control of accidents within the design basis Control of severe plant conditions, including prevention of accident progression and mitigation of the consequences of severe accidents Mitigation of radiological consequences of significant release of radioactive materials Essential Means Conservative design and high quality in construction and operation Control, limiting & protection systems and other surveillance features Engineered safety features and accident procedures Complementary measures and accident management Off-site emergency response

20 GSR Part 4 (Multiple Barriers)

21 GSR Part 4 (Multiple Barriers) exclusion area boundary (virtual barrier) shield building steel containment or liner pressure vessel fuel cladding exclusive zone fuel pellet

22 GSR Part 4 Redundancy

23 GSR Part 4 Diversity

24 GSR Part 4 Requirement 9: Assessment of the provisions for radiation protection It shall be determined in the safety assessment for a facility or activity whether adequate measures are in place to protect people and the environment from harmful effects of ionizing radiation.

25 GSR Part It has to be determined in the safety assessment whether adequate measures are in place to control the radiation exposure of workers and members of the public within relevant dose limits (as required by Principle 6 [1]), and whether protection is optimized so that the magnitude of individual doses, the number of people exposed and the likelihood of exposures being incurred have all been kept as low as reasonably achievable, economic and social factors having been taken into account (see Principle 5 [1]).

26 GSR Part In the safety assessment of the provisions for radiation protection, normal operation of the facility or activity, anticipated operational occurrences and accident conditions have to be addressed.

27 GSR Part 4 Proven engineering practices Defense in depth Radiation protection Safety classification Protection against internal and external hazards Combination of loads Selection of materials Single failure criterion Redundancy, diversity Equipment qualification Ageing Man-machine interface, etc.

28 GS-G-1.2 Verification of Safety Analysis In carrying out its review and assessment, the regulatory body should determine whether the operator has defined criteria which meet the safety objectives and requirements relating to: (1) Engineering design; (2) Operational and managerial aspects; and (3) Normal operation and fault conditions.

29 SSR-2/1 Requirement 19: Internal and external hazards All foreseeable internal hazards and external hazards, including the potential for human induced events directly or indirectly to affect the safety of the nuclear power plant, shall be identified and their effects shall be evaluated. Hazards shall be considered for determination of the postulated initiating events and generated loadings for use in the design of relevant items important to safety for the plant.

30 SSR-2/1 Requirement 22: Safety classification All items important to safety shall be identified and shall be classified on the basis of their function and their safety significance.

31 SSR-2/1 Requirement 25: Single failure criterion The single failure criterion shall be applied to each safety group incorporated in the plant design.

32 SSR-2/1 Requirement 30: Qualification of items important to safety A qualification programme for items important to safety shall be implemented to verify that items important to safety at a nuclear power plant are capable of performing their intended functions when necessary, and in the prevailing environmental conditions, throughout their design life, with due account taken of plant conditions during maintenance and testing.

33 SSR-2/1 Requirement 30: Qualification of items important to safety Equipment Qualification(IAEA Safety Reports No. 3) : Generation and maintenance of evidence to ensure that the Equipment will operate on demand to meet system performance requirements. Environmental Qualification Seismic Qualification EMI/RFI Qualification

34 SSR-2/1 Requirement 31: Ageing management The design life of items important to safety at a nuclear power plant shall be determined. Appropriate margins shall be provided in the design to take due account of relevant mechanisms of ageing, neutron embrittlement and wear out and of the potential for age related degradation, to ensure the capability of items important to safety to perform their necessary safety functions throughout their design life.

35 Summary Engineering Factors to Important to Safety Defense in depth (Multiple Barriers) Redundancy Diversity Radiation protection, etc.