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[en] The Fukushima-Daiichi accidents in 2011 underlined the importance of severe accident management (SAM), including external events, in nuclear power plants (NPP) and the need of implementing efficient mitigation strategies. To this end, the EURATOM work programmes for 2012 and 2013 was focused on nuclear safety, in particular on the management of a possible severe accident at the European level. Relying upon the outcomes of the successful EURATOM SARNET and SARNET2 projects, new projects were launched addressing the highest priority issues, aimed at reducing the uncertainties still affecting the main phenomena. Among them, PASSAM and IVMR project led by IRSN, ALISA and SAFEST projects led by KIT, CESAM led by GRS and sCO2-HeRO lead by the University of Duisburg-Essen. The aim of the present paper is to give an overview on the main outcomes of these projects. (authors)
[en] The first time I met George was in March 1998 for dinner. And the last time I had dinner with him was in March of last year, or two decades later exactly. During the first evening, we discussed and confronted our strategies for the short period of time left then until his retirement in 2004; was it sufficient time to contribute to the discipline with something risky and innovative? During the last four-hour dinner, after having evoked life and death rather joyfully and serenely, we looked back and analysed what came out of our two decades of collaboration. This paper, which was prepared with the aim to portray George’s achievements in thermal-hydraulics during the last 20 years of our partnership (1998–2018), is written in the spirit of narrating our epilogue culinary-science-talk, while trying to be faithful to his thoughts and ideas about the developments of the discipline and its perspectives. The paper introduces first the cascade of computational tools and discusses trends related to reactor safety problems and developments needed, as well as the need for new kinds of refined experimental data. Although George was not directly involved in all the examples presented here, he felt so concerned about the success of each project/case presented in this paper that he was virtually part of it; and as he wrote in our last paper (Yadigaroglu and Lakehal, 2016): this is after all his near-home work. Finally, in memory of the two other great scientists who have left us recently, Geoff Hewitt and Sam Martin, the content of the paper includes two cases in which both of them had collaborated directly or indirectly.
[en] The paper focuses on the performance of reflector trap passive safety system incorporated in the GFR 2400 reactor design. Multiple studies are raising question about the technical feasibility of the GFR 2400 concept, thus the new neutron trap passive system is introduced in the paper to cope with abnormal operation of this reactor. The coupled calculation scheme is used in the paper, where NESTLE code is used for coupled steady state and transient simulations of the reactor performance. The NESTLE code system solves multi-group transient diffusion equation utilizing nodal expansion method and is internally coupled with thermal-hydraulic sub-channel code. The SCALE6 software package is used for processing of macroscopic multi-group cross-sections that are used in the NESTLE code. The performance of the neutron trap passive system is simulated by the developed model for typical abnormal transients, such as control rod withdrawal or primary blower shutdown during the full power operation. Curie point latch acts as the actuation mechanism of the passive system. Temperature distributions are studied and the applicability of the neutron trap passive safety system is discussed in the paper. (author)
[en] A diagram presents the whole of the works that will be made on the French fleet of nuclear reactors. The diagram includes the works necessary for the decenal reviews, the lifetime extension projects, usual reactor maintenance and the post-Fukushima measures. (A.C.)
[en] Conclusion: • Since there are various technical choices, safety design standard for Gen-IV reactors should include commonly applicable, technology-neutral criteria. • Appropriate combination of deterministic and risk-informed approach should be pursued aiming at rational safety design. • Since SFR and LFR have common aspects as LMFR, consistency as LMFR safety design criteria is important in SFR SDC and LFR SDC. • On the other hand, clarification of SFR and LFR specific safety design criteria is also important.
[en] Background: In the TWG-GCR a clear need has been identified by the MS to develop mHTGR Safety Design Criteria. The development and implementation of comprehensive safety design criteria (SDC) that take HTGR-specific characteristics into account would provide a high level of assurance that modular HTGRs are consistently designed, constructed, and operated in a manner that takes advantage of these intrinsic properties, while also avoiding unintended compromises in plant safety.
[en] Last week, Japanese people had a so sad memory of day, March 11th, on the huge earthquake, tsunami, and 1F accident. So many people, more than 40,000, are still evacuated from their hometown due to the influence of the radio active materials released by 1F accident. Nuclear engineers and researchers, not only in Japan but over the world, thought again how the safety of nuclear is significant and our responsibility. Today, it is our great opportunity to discuss not only for safety but also sustainable and clean energy supply systems using nuclear, together with IAEA specialists and GIF members.
[en] In Great Britain, the drop in reactivity that occurs when nuclear fuel is irradiated in a nuclear power reactor has typically not been claimed. Instead, criticality safety assessments have normally assumed that the fuel is unirradiated with no reduction in the fissile material present. Although this 'fresh fuel' approach is conservative, it leads to an overestimation of the calculated neutron multiplication factor (keff) and may lead to additional operational burdens being placed upon duty-holders. In future, it is possible that GB duty-holders may take credit for the reduction in reactivity, known as 'burn-up credit', that occurs when fissile material is consumed in a nuclear reactor. In order to provide authoritative and independent information on the key aspects of burn-up credit, the Office for Nuclear Regulation (ONR) commissioned a research project. This paper provides an overview of the key findings of this research and potential implications for the regulation and management of criticality safety in GB. A 'Regulator Question' set for use when assessing criticality safety cases is given that is intended to aid both regulator and duty holder in their assessments, which enables regulatory attention to be targeted proportionately on those areas of most importance
[en] The safety of sodium-cooled fast reactors (SFR) is reviewed. The following risks are detailed: the risks of chemical reactions between air and sodium and between water and sodium, the risk of thermodynamical interactions between water and sodium, the risk of interaction between sodium and the nuclear fuel, the risk of frozen coolant, and the risk of the deterioration of steels in the presence of sodium. It is to note that some specificities of SFR make them sensitive to particular events; these specificities are a high power density in the reactor core and less favorable neutron counter-reactions than in water-cooled reactors. Sodium can absorb a large part of fission products (barium, iodine,...) but not cesium and fission gases in case of core meltdown. Several SFR of significant output power were operating in the US, France, United-Kingdom, Russia and Japan, so an important feedback is available. (A.C.)
[en] Goal of RSWG [Risk and Safety Working Group]: • Promote a consistent approach on safety, risk, and regulatory issues between Generation IV systems; • Propose safety principles, objectives, and attributes based on Gen-IV safety goals to inform R&D plans; • Support implementation of technology-neutral Integrated Safety Assessment Methodology (ISAM); • Collaborate with System Steering Committees, consult with other methodology working groups and task forces; • Interface with IAEA (INPRO, Safety), OECD/NEA (WGSAR) and other regulatory stakeholders.