NUGENIA/TA2 Achievements in Severe Accidents Research (2015-2020)

Severe accident research is the only way to achieve the best possible management in case such unlikely events eventually happen. Early this century, the Severe Accident Research NETwork (SARNET) was born as an EC project and about 10 years later it became the technical area 2 of NUGENIA, the SNETP (Sustainable Nuclear Energy Technological Platform) pillar devoted to research on Gen. II and Gen. III Light Water Reactors (LWRs). This paper describes the most relevant outcomes from NUGENIA/TA2 research in the last five years concerning coolability of in-vessel and ex-vessel corium/debris, in-containment phenomena and source term; besides, the progress made and underway on severe accident modelling is outlined. Finally, the NUGENIA/TA2 commitment to knowledge dissemination through courses and conferences is highlighted

Overview on hydrogen risk research and development activities: Methodology and open issues

During the course of a severe accident in a light water nuclear reactor, large amounts of hydrogen can be generated and released into the containment during reactor core degradation. Additional burnable gases [hydrogen (H2) and carbon monoxide (CO)] may be released into the containment in the corium/concrete interaction. This could subsequently raise a combustion hazard. As the Fukushima accidents revealed, hydrogen combustion can cause high pressure spikes that could challenge the reactor buildings and lead to failure of the surrounding buildings. To prevent the gas explosion hazard, most mitigation strategies adopted by European countries are based on the implementation of passive autocatalytic recombiners (PARs). Studies of representative accident sequences indicate that, despite the installation of PARs, it is difficult to prevent at all times and locations, the formation of a combustible mixture that potentially leads to local flame acceleration. Complementary research and development (R&D) projects were recently launched to understand better the phenomena associated with the combustion hazard and to address the issues highlighted after the Fukushima Daiichi events such as explosion hazard in the venting system and the potential flammable mixture migration into spaces beyond the primary containment. The expected results will be used to improve the modeling tools and methodology for hydrogen risk assessment and severe accident management guidelines. The present paper aims to present the methodology adopted by Institut de Radioprotection et de Sûreté Nucléaire to assess hydrogen risk in nuclear power plants, in particular French nuclear power plants, the open issues, and the ongoing R&D programs related to hydrogen distribution, mitigation, and combustion. © 2015, Published by Elsevier Korea LLC on behalf of Korean Nuclear Society

Combustion properties of H2/N2/O2/steam mixtures

International audienc

HYDROGEN MANAGEMENT STRATEGIES AND ANALYSIS CODES IMPLEMENTED BY THE OECD/NEA MEMBER COUNTRIES

In the follow-up to the Fukushima accident, the OECD/NEA CSNI initiated an activity within its member countries to review and assess their hydrogen management strategies under severe accident conditions and the associated computer codes used for the hydrogen safety analysis. A CSNI report, titled Hydrogen Management and Related Computer Codes, was thereafter published by OECD/NEA in 2014 June, consisting of information contributed by 15 OECD/NEA member countries. This paper summarizes the major findings obtained in the activity. The state of knowledge on hydrogen generation, distribution, combustion and mitigation is presented. The corresponding computer codes that are used by the member countries for hydrogen safety analysis are discussed, including code capabilities and validation status assessed against the hydrogen behavior associated with generation, distribution, combustion and mitigation. The hydrogen management strategies are presented based on the literature findings. The status of hydrogen management systems implemented by the member countries are discussed, including national requirements, mitigation measures and their implementation status, and considerations on the interaction of engineering safety systems with hydrogen behavior during severe accidents. The CSNI report has provided a basis for assessing severe accident management strategies and identifying gaps in code capabilities and validations, and providing insights for model enhancement and application. It is expected to be a useful handbook for nuclear safety authorities, research institutions, and utilities.JRC.F.5-Nuclear Reactor Safety Assessmen