20.500.12556/DiRROS-28402 Detailed assessment of combustion risk and PAR efficiency in the late phase of a severe accident within the European AMHYCO project The European AMHYCO project aims at enhancing the understanding of H2/CO combustion risk within the containment of a light water reactor nuclear power plant during the in- and ex-vessel phase of a severe accident. The goal is to incorporate this knowledge into severe accident management guidelines (SAMG) and give recommendations for long-term operation upgrades. Based on a critical review of established methodologies and practices related to combustion risk assessment, as well as the identification of accident sequences where the containment integrity may get challenged, experimental investigations were conducted to close knowledge gaps related to combustion characteristics and the operation of passive autocatalytic recombiners under late phase conditions. To prepare the basis for the further assessment and refinement of existing SAMGs, systematic and detailed analyses of the most challenging scenarios and possible mitigative measures were conducted for three generic European pressurized water reactor (PWR) containment designs, namely KWU, Westinghouse, and VVER. For each reactor type, one Loss of Coolant Accident and one Station Blackout scenario were selected for detailed analyses with a variety of different numerical codes. Both scenarios cover a range of in-containment atmospheric conditions from potentially flammable at medium pressure to a steam-inerted atmosphere at high pressure, including the late phase with an active filtered containment venting system (FCVS). This paper outlines the employed methodology using a consecutive analysis chain consisting of three levels with increasing level of detail (system codes, 3D GOTHIC™ and CFD) to assess containment pressurization, efficiency and/or options of individual mitigation measures regarding H2/CO combustion risk and equipment and instrumentation survivability. As a common basis, the system code nodalization schemes and 3D models are developed from detailed CAD geometries. On the basis, the paper summarizes the outcome of the work with a focus on the comparative assessment of the impact and effectiveness of mitigative measures (passive autocatalytic recombiner, containment sprays, FCVS) on the combustion risk in the accident. The analyses highlight that without combustible gas mitigation, containment atmospheres develop combustible pockets and may even become globally flammable, highlighting the need for control systems to preserve integrity. PARs proved effective across all scenarios in preventing large clouds with flame acceleration conditions, with their capacity mainly influencing depletion rates and timing. Oxygen removal by PARs also enables safe operation of containment and core cooling systems without increasing combustion risk in the late phase. combustion risk AMHYCO project containment reponse nevarnost gorenja preprečevanje nesreč projekt AMHYCO true false true Elsevier Nizozemska Angleški jezik Slovenski jezik © 2025 The Author(s). Neznano 2026-03-18 12:56:28 2026-03-18 12:56:29 2026-03-24 03:59:54 0000-00-00 00:00:00 2026 0 0 Nasl. z nasl. zaslona; Soavtor iz Slovenije: Ivo Kljenak; Opis vira z dne 15. 10. 2025; str. 1-15 pt. B, [article no.] 114588 Vol. 446 Jan. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2025-01-31 2025-11-02 2025-11-19 621.039.58 1872-759X 10.1016/j.nucengdes.2025.114588 272098563 https://www.sciencedirect.com/science/article/pii/S0029549325007654?via%3Dihub 1 8241adc0-22c1-11f1-a33f-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=42004 RAZ_Kelm_Stephan_2026.pdf RAZ_Kelm_Stephan_2026.pdf 1 8D236A52882E149D2A5CF0D87983490E 1aadd7e34c1478910daa14242b35ae825869840ae26dad1b2788fc0e8bff30ea cce1faff-22c1-11f1-a33f-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=42005 Institut Jožef Stefan 0 0 0