Modelling of stratification and mixing of a gas mixture under the conditions of a severe accident with intervention of mitigating measures

M. Andreani (1) , M. Sharabi (1) , A. Bleyer (2) , J. Malet (2) , F. Dabbene (3) , D. Visser (4) , S. Benz (5) , Z. Xu (5) , Z. Liang (6) , S Kelm (7) , A. Filippov (8) , A. Zaytsev (9) , M. Kamnev (10) , O. Tyurikov (10) , C. Boyd (11)

1 LNS - Laboratory for Neutron Scattering and Imaging [Paul Scherrer Institute]
2 IRSN - Institut de Radioprotection et de Sûreté Nucléaire
3 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
4 Nuclear Research and Consultancy Group
5 KIT - Karlsruher Institut für Technologie
6 Canadian Nuclear Laboratories
7 FZJ - Forschungszentrum Jülich GmbH | Centre de recherche de Jülich | Jülich Research Centre
8 INR - Institute for Nuclear Research of Russian Academy of Sciences
9 JSC SSC RF – IPPE
10 JSC - Jülich Supercomputing Centre
11 U.S.NRC - United States Nuclear Regulatory Commission

One of the objectives of the ERCOSAM-SAMARA projects was to assess capabilities of the current computational tools to predict the evolution of gas distribution in the containment under conditions relevant to a severe accident with hydrogen release. Various Lumped Parameter (LP) and CFD codes were used for the planning calculation, and pre- and post-test analyses. The planning calculations provided useful information for determining the most appropriate configurations, initial and boundary conditions used in the experiments. Pretest calculations were performed for nearly all the tests, using nominal initial and boundary conditions provided in the test protocols, which resulted in discrepancies for the pressurisation rate, due to a large (and unexpected) sensitivity of the results to the initial conditions. In general, all the codes were able to capture the stratification build-up. Regarding the last phase of the tests, the pressure trends were properly reproduced and the effectiveness of various mitigation devices on gas mixing was properly represented although large discrepancies remain between calculations and measurements. Finally, post-test simulations were carried out using the actual initial and boundary conditions, and making use of the knowledge on various phenomena acquired in the pre-test analyses. Although in general pressure and gas distribution evolution could be properly represented, various discrepancies between simulations and data show that the representation of some phenomena would require additional analysis and refined modelling.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

M. Andreani, M. Sharabi, A. Bleyer, J. Malet, F. Dabbene, et al.. Modelling of stratification and mixing of a gas mixture under the conditions of a severe accident with intervention of mitigating measures. ICAPP 2015 - International Congress on Advances Nuclear Power Plants, May 2015, Nice, France. ⟨cea-02509249⟩