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[en] SDC Development Background & Objectives: • Safety Design Criteria (SDC) Development for Gen-IV SFR: – Proposed at the GIF Policy Group (PG) meeting in October 2010 –SDC “harmonization” is increasingly important for: • Realization of enhanced safety designs meeting to Gen-IV safety goals and safety approach common to SFR systems; • Preparation for the forthcoming licensing in the near future; • Because Gen-IV SFR are progressing into conceptual design stage. • The SDC is the Reference criteria: – Of the designs of safety-related Structures, Systems & Components that are specific to the SFR system; – For clarifying the requisites systematically & comprehensively; – When the technology developers apply the basic safety approach and use the codes & standards for conceptual design of the Gen-IV SFR system
[en] Seismic PSA was carried out for a typical liquid metal cooled fast breeder reactor (LMFBR) in order to study the rationalized seismic design, maintaining and/or improving safety during seismic event. The seismic sequence quantification identifies the dominant structures, systems and components (SSCs) to the seismic core damage frequency (CDF). The sensitivity analyses by reducing or increasing the seismic capacity for SSCs are used to examine the optimized seismic design in view of safety and economical aspects. The LMFBR-specific risk-significant SSCs are reactor coolant boundary, decay heat removal coolant path and reactor control rod, which are different from those of light water reactors (LWRs). The electrical power supply system has a minor contribution to the seismic CDF. The sensitivity study shows that passive safety features of LMFBRs are important to maintain and/or enhance seismic capacity. The passive safety includes the decay heat removal capability via natural circulation and safety measures without depending on the support systems such as alternating current (AC) electrical power, for example. On the course of seismic sequence quantification, a methodology to evaluate the probability of seismic-induced multiple failure has been developed and applied to the decay heat removal function. The results suggest the multiplicity of the triply redundant system is to be considered for the significant components such as the decay heat removal path when one considers the difference in the seismic response
[en] Concluding remarks: • The Interim Safety Design Criteria (SDC) report is provided to IAEA, being ready to start technical interaction with IAEA. • The updated SDC report will be delivered to next GIF PG meeting in May with the incorporation of the feedback from the joint GIF/IAEA SFR SDC workshop. • The SDC report would be disseminated and utilized for SFR design at international level. • Safety improvement comes from continuous efforts for updating safety designs: – It is enhanced by the new safety technology and recent knowledge related to the operation experiences and R&D outcomes; – In this sense, the SDC will be updated with the times as necessary, by including constructive feedbacks from all the international technical entities including regulatory bodies.
[en] RSWG - Purpose: • Primary objective – promote consistent approach on risk, safety, and regulatory issues between Generation IV systems. • Elements of Work Scope: – Propose safety principles, objectives, and attributes based on Gen IV safety goals to guide R&D plans – Propose a technology-neutral framework of safety criteria and assessment methodologies; – Test and demonstrate the applicability of the framework and assessment methodologies; – Provide consultative support to System Steering Committees and other Gen IV entities; – Undertake appropriate interactions with regulators, IAEA, and other stakeholders.
[en] Japanese Government Report to the IAEA: 28 Key Points in 5 Groups as Lesson Learns from the Accident. Group 1: Strengthen preventive measures against a severe accident: 1. Strengthen measures against earthquakes and tsunamis. 2. Secure power supply. 3. Secure a firm cooling function of a reactor and a RCV. 4. Secure a firm cooling function of spent fuel pools. 5. Thorough accident management (AM) measures. 6. Response to issues in concentrated siting of reactors. 7. Consideration on basic design such as placement of NPS, etc.. 8. Ensuring the water-tightness of important equipment facilities. Group 2: Enhancement of measures against severe accidents: 9. Enhancement of prevention of hydrogen explosion. 10. Enhancement of containment vent system. 11. Enhancement of accident response environment. 12. Enhancement of the radiation exposure management system at accident. 13. Enhancement of training responding to severe accident. 14. Enhancement of instrumentation reactors and PCVs. 15. Central control of emergency supplies and equipment and rescue team in place. Group 3: Enhancement of nuclear emergency response: 16. Response to combined emergency of both large-scale natural disaster and nuclear accident. 17. Reinforcement of environment monitoring. 18. Segregation of duties between relevant central and local organizations, etc. 19. Enhancement of communication on the accident. 20. Enhancement of response to support from overseas and communication to the international community. 21. Adequate identification and forecast of effect of released radioactive materials. 22. Clear definition of widespread evacuation area and radiological protection guideline in nuclear emergency. Group 4: Reinforcement of safety infrastructure: 23. Reinforcement of safety regulatory bodies. 24. Establishment and reinforcement of legal structure, criteria and guidelines. 25. Human resources for nuclear safety and nuclear emergency preparedness. 26. Securing independency and diversity of safety system. 27. Effective use of Probabilistic Safety Assessments (PSA) in risk management. Group 5: Raise awareness of safety culture: 28. Raise awareness of safety culture
[en] Background: • Safety Design Criteria (SDC) Development for Gen IV Sodium-cooled Fast Reactor (SFR) – Proposed at the Policy Group (PG) meeting in October 2010 – SDC “harmonization” is increasing important for: • Realization of enhanced safety designs common to SFR systems, • Preparation for the forthcoming licensing in the near future • Because Gen-IV SFR are progressing into conceptual design stage • “Upper level” safety standards for the Gen IV have been developed so far: – Safety and reliability goals for Generation IV Nuclear Energy Systems in the “GIF Roadmap” (2002) – “Basis for safety approach for design and assessment of Generation IV Nuclear Systems” (2008) – Design requirements of the SFR systems in the “SFR System Research Plan [SRP]” (2007) • There is still a large gap between “upper level” and “base level” of codes and standards which will referenced and used for designing Gen IV SFR
[en] Safety-related Experiences in Joyo: • Experiments [selected]: – Fundamental Characteristics of Fast Reactor Core & Fuel e.g. Fuel Temp. Reactivity, Void Reactivity, Pellet structural changes with burnup; – Natural Circulation Capability Tests [Partial & Full Power conditions]; – Simulation tests of fuel pin breach; – In-core temperature measurement using optical fiber; – Sheilding [for Mark-III power upgrade]; – SASS Magnetic Irradiation Tests; • Operation & Maintenance [selected]: – Plant & Core Monitoring; – Mitigation Behaviors of Fission Products & Corrosion Products; – Upgrade of Na Purification System in primary loop; – Interim Heat Exchanger renewal for Mark-III update.
[en] Safety Design Guidelines (SDG) Development: • Main objective: – to support practical application of SDC in design process for improving safety in specific topical areas: »including use of inherent/passive safety features; »design measures for prevention and mitigation of severe accidents. – Initial topical areas are considered: »Particular importance since a fast reactor core is typically not in its most reactive configuration; »Quantification of key criteria for safety improvement
[en] Concluding Remarks: – Concept of DiD shall be applied to the safety design of advanced SFR. – Safety level can be further improved especially by enhancing prevention and mitigation features with more emphasis on passive safety features. – Through prevention, detection, and control of accident, CDA shall be excluded from DBE. – Toward a commercialization of SFR, not only prevention but also mitigation of typical severe core damage are necessary to be enhanced. – In particular, the safety approach with elimination of severe recriticality is highly desirable and will contribute to establish public acceptance of the SFR.
[en] Status of Update on GIF SDC Report: • Feedbacks from External Reviews have been incorporated in the Updated SDC Report; • Consideration on IAEA SSR 2/1 update in 2016 for LWR safety design requirement: – IAEA SSR 2/1 has been updated based on lessons learned from Fukushima Daiichi Nuclear Accidents; – GIF SDC Task Force needs clarification before incorporation of updates; – To be discussed at this Workshop