SARNET2 benchmark on air ingress experiments QUENCH-10, -16

• Published in: Annals of nuclear energy Vol. 74; no. C; pp. 12 - 23
• Main Authors: Fernandez-Moguel, Leticia, Bals, Christine, Beuzet, Emilie, Bratfisch, Christian, Coindreau, Olivia, Hózer, Zoltan, Stuckert, Juri, Vasiliev, Alexander, Vryashkova, Petya
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2014; Elsevier Masson
• Subjects: Air flow; Air oxidation; Benchmark; Benchmarking; Boundary conditions; Coolability; Mathematical models; Modelling; Nuclear reactor components; Oxidation; Physics; Reflood; Zirconium alloy; Zirconium alloy; Benchmark; Modelling; Reflood; Air oxidation; Coolability
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2014.05.013

•Two similar QUENCH air ingress experiments were analysed with eight different codes.•Eight institutions have participated in the study.•Differences in the code were mostly small to moderate during the pre-oxidation.•Differences in the code were larger during the air phase.•Study has proven that there are physical processes that should be further studied. The QUENCH-10 (Q-10) and QUENCH-16 (Q-16) experiments were chosen as a SARNET2 code benchmark (SARNET2-COOL-D5.4) exercise to assess the status of modelling air ingress sequences and to compare the capabilities of the various codes used for accident analyses, specifically ATHLET-CD (GRS and RUB), ICARE-CATHARE (IRSN), MAAP (EDF), MELCOR (INRNE and PSI), SOCRAT (IBRAE), and RELAP/SCDAPSim (PSI). Both experiments addressed air ingress into an overheated core following earlier partial oxidation in steam. Q-10 was performed with extensive preoxidation, moderate/high air flow rate and high temperatures at onset of reflood (max Tpct=2200K), while Q-16 was performed with limited preoxidation, low air flow rate and relative low temperatures at reflood initiation (max Tpct=1870K). Variables relating to the major signatures (thermal response, hydrogen generation, oxide layer development, oxygen and nitrogen consumption and reflood behaviour) were compared globally and/or at selected locations. In each simulation, the same input models and assumptions are used for both experiments, differing only in respect of the boundary conditions. However, some slight idealisations were made to the assumed boundary conditions in order to avoid ambiguities in the code-to-code comparisons; in this way, it was possible to focus more easily on the key phenomena and hence make the results of the exercise more transparent. Remarks are made concerning the capability of physical modelling within the codes, description of the experiment facility and test conduct as specified in the code input, and code limitations that might warrant additional research to support model improvements, especially the modelling of nitride formation and melt oxidation.