Karl-Fredrik Nilsson, Institute for Energy and Transport, JRC ESNII+ Workshop Brussels Oct 22, 2015 The CEN-WS64 Phase 2: PG2 Towards a European Design Code for Innovative Nuclear Reactors The presentation is based on ongoing discussions and not an official position of the European Commission.

Outline CEN-WS 64 Phase 2 Background and Objectives General Design Code Requirements Members & Applied Methodology for CEN WS-64 PG2 Identified items for Code Evolution Conclusions

Status of global nuclear code development Existing nuclear codes o Civil work: AFCEN ETC-C (RCC-CW) o Mechanical equipment: AFCEN (RCC-M, RCC-MRx, RSE-M), ASME, KTA, JSME, NIKIET o Electrical and I&C systems and equipment: AFCEN (RCC-E), Standards issued by American IEEE, Korean standards derived from IEEE, ANSI, NEMA: KEPIC EN, EM, EE…, KTA Most are produced by national organizations Tentative harmonization processes in some areas (MDEP…), but: o they are generally not industry initiative o they involve a limited number of countries

Status of nuclear industry in Europe Europe has o a first-rank regional reactor fleet in the world o an high-skilled experienced industry in all nuclear areas o But an inhomogeneous approach of design, construction and maintenance of nuclear facilities due to diverse national regulations, industrial doctrines, etc. For the European Commission: o the two first points are advantages (strengths) that should be promoted to increase the value of European nuclear industry; o in this respect, the industrial approaches are to be harmonized to gain competitiveness in the global market Codes customized to the European industrial needs should contribute to this aim As AFCEN codes constitute a consistent set, adaptable to national regulations and are proposed as a basis for this exercise

Answer: CEN WS 64 – phase 2 Answer: CEN WS 64 – phase 2 o AFCEN proposal to make its codes evolve, taking into account the needs and expectations of European stakeholders o Two avenues are considered: o for short-term needs : to implement code modifications as part of AFCEN subcommittees work; o for medium and long-term needs : to collect and to integrate them in the codes in the framework of a CEN Workshop, Objectives of the CEN Workshop: 1.recommend medium-long term evolution of AFCEN codes; 2.identify the R&D associated needs; 3.look for explicit or implicit references to national standards in the codes and propose their substitution by international standards or; 4.interact with the Multinational Design Evaluation Programme (MDEP)

Organization of CEN WS 64 – phase 2

Links between the partners

CEN WS64 Phase 2 Schedule

General Requirements supported by Design Codes Reactor safety at least same level as Gen III+ Post-Fukushima: Increased demand to demonstrate safety under accident conditions Overall Cost Efficient licensing Components (material, size, design, fabrication) Maintenance Reduce undue conservatism

Approach for Design Code Return-of-Experience Pre-normative Research Robust Engineering IAEA Safety Standards Safety of Nuclear Power Plants: Design Specific Safety Requirements No. SSR-2/ Where an unproven design or feature is introduced or where there is a departure from an established engineering practice, safety shall be demonstrated by means of appropriate supporting research programmes, performance tests with specific acceptance criteria or the examination of operating experience from other relevant applications.

PG2 members 1.JRC: K-F Nilsson (Convener) and S. Holmström 2.CEA: C. Pétesch (AFCEN representative) 3.STUK: M. Bäckström; 4.SCKCEN: D. Lambert; 5.ENEA: D. Bernardi, ENEA; 6.AMEC-Foster Wheeler: D. Buckthorpe/A. Wisbey 7.AREVA: S. Dubiez-Le Goff; 8.Tractebel: J. Belche; Potential new members 1.UJV: P. Hayek; 2.ANSALDO: M. Iamele; 3.EDF: M. Blat; Additional Members are welcome!

PG2 Organization of Work 1 1.Brainstorming for proposal of topics with shorter presentations; 2.Detailed Technical presentation(s) of selected topic by one or several experts. After the discussion the group decides whether a proposal should be prepared for the next meeting, or if the topic should be taken up at a later stage, or if it should not be pursued further; 3.Presentation of Code Evolution/R&D proposal (Code Evolution and/or R&D) by one or several experts; 4.Finalization of Code Evolution/R&D proposal.

Only 2-4 topics are addressed in parallel Broad and complex issues such as 60 years design life could be split into sub-topics for which separate proposals are done Proposals need not be over-worked. It is more important that proposals are submitted at continuous rate. PG2 Organization of Work 2

TopicStatusLeader 1 Environmental degradation of material in HLM coolants Code Evolution and R&D proposals done SCKCEN/ JRC 2 Weld procedures and weld performance Some technical presentations Key issue 2016 cross-cutting PG1 Tracteb/ AMEC 3 High temperature data for accident situation Technical presentation Draft proposal under preparation AMEC/CEA 4Miniature test Procedures Technical presentation. Follow-up in 2016 JRC 5 Long-term degradation, 60 years design life, property extension Technical Presentations. R&D proposal for long-term creep under preparation Key issue 2016 Cross-cutting PG1 AREVA/JRC 6 High temperature degradation (creep, creep-fatigue, ratcheting, buckling) Technical presentation based on MATTER project Code evolution and R&D proposal in preparation JRC 7Inclusion of new materials fabrication, codification Technical presentation Inclusion of Ni-based alloys CEA/AMEC PG2 Topics discussed 1

TopicStatusLeader 8 Coating and surface treatments Some technical presentations AREVA /ENEA 9 High irradiation degradation No Technical presentation Also covered by 60-years design life TBC 10 Fuel cladding design rules Not part of Design Code RCC-MRx. Will not be elaborated on. - 11Residual stresses No detailed discussion yet. Part of welds TBC 12 Comparison of codes ASME/AFCEN/KTA/EN Ongoing Cross-cutting with PG1 STUK 13 On-line enabled material data base Not discussed in detail yet. Cross-cutting with PG1 JRC 14Modernized Design Rules – Design by Analysis including FEM Some technical presentation Cross-cutting with PG1 CEA PG2 Topics discussed 2

Key Topics for Gen IV Code Development 1.Compatibility Heavy Liquid Metal/component 2.High Temperature Life Assessment 3.60-years Design-Life

Compatibility HLM coolant & structure Lead, as opposed to sodium, induces strong environmental effects (embrittlement, corrosion, erosion); The chemical composition of the coolant has a large impact; Limited feedback experience of HLM coolants. Implict Code Assumptions The chosen material has the same behaviour as in air, except for depletion of corrosion allowance; ISI will detect degradation when it becomes critical; Composition stays within allowable range in the entire system. Gavrilov et al. SCKCEN

Compatibility HLM coolant & structure Approach 1: Immunity Demonstrate "immunity" and Implicit Code Assumptions  P91 ruled out due to LME  316L OK?, welds? Requires extensive qualification programme Approach 2: Probationary Rules Accept some degradation effects but ensure sufficient margins through reduction factors, inspection programmes Requires substantial associated pre- normative R&D General problem: lack of long-term data at operational conditions

High Temperature Safety and Life Assessment Life assessment Creep Creep-fatigue Ratcheting Thermal buckling  Remove undue conservatism, improved models/Design Rules, Design-by-Analysis High Temperature Data for Accident Analysis  Extend temperature range in the code Extend materials codified E.g. High Alloy Steels (800H, 617, 230)

High Temperature Safety and Life Assessment Creep-fatigue Design Rules in the Codes: Interaction Diagramme Separate creep and fatigue assessment but no creep-fatigue interaction; Depends on "creep" model; Large scatter in predictions; Often overly conservative, but in some cases non-conservative (cyclic softening material); Questionable for long hold-times Restricted to iso-thermal conditions Alternative ? Models that incorporates creep and fatigue and are simpler to apply (Wilshire model developed in the MATTER project)

 Design Codes assumes 40 years Design Life but future reactors should operate for at least 60 years  60-years operation life must be based on "60 years Design" and Plant Life Management 60+-Years Design Life  For the 60+ year Design Life all relevant slow processes and their interactions need to be taken into account Creep, Fatigue, Irradiation, Thermal ageing, Environmental  The main issue is long-term material properties. The "rule of thumb" is that an acceleration factor of 3 is acceptable  20 years test needed for 60 years design life! Creep strain for unexposed and aged P91 steel (Swindemann)

60+Years Design Life How get relevant material data for 60+ design life? Testing of materials exposed to long-term operational conditions Extrapolation of accelerated tests. This requires that: The deformation mechanism and microstructural evolution is the same in the accelerated test as the operational conditions, or at least We can predict the change in deformation mechanism and microstructural evolution  Integration of physics-based models at different and time scales Creep rupture curves Creep Deformation maps

The overall goal of the CEN WS-64 Phase 2 is to promote a closer more homogenized approach to reactor design through "Europeanization" of Design Codes To this end AFCEN codes are used, and for innovative reactors: RCC-MRx Innovative designs are at the edge or even beyond the scope of existing technical code and there is very limited "return of experience" Thus Code development must be accompanied by pre-normative research Summary & Conclusions

The main outputs of the CEN WS-64 Phase 2 are : Proposals for AFCEN long and medium-term Code Evolution  AFCEN Proposals for associated R&D  DG-RTD Summary & Conclusions A large number of topics have been identified. Key topics include: Heavy Liquid Metal Coolant/solid interaction 60+ years Operational Life High-Temperature Degradation Welded components A bottleneck is the lack of material data for representattive of exposure to long-term operational conditions.

Thanks for your attention. Any questions?