Development of severe accident simulation code for sodium-cooled fast reactors: SIMMER-V, 1; Overview of the SIMMER-V code development

Tagami, Hirotaka ; Ishida, Shinya  ; Okano, Yasushi; Yamano, Hidemasa   ; Kubo, Shigenobu ; Payot, F.*; Saas, L.*; Trotignon, L.*; Gubernatis, P.*; Dufour, E.*; Tobita, Yoshiharu

JAEA has been developing the SIMMER-V code in collaboration with CEA to perform severe accident (SA) simulations of future sodium-cooled fast reactors (SFRs) including a unique core design with large-scale heterogeneous cores. An SA sequence in SFRs has been analyzed by: the SAS4A code for the Initiation Phase (IP), in which fuel pin disruption and vertical fuel dispersion occur in individual fuel subassemblies; and the two-dimensional SIMMER-III or three-dimensional SIMMER-IV code for the Transition Phase (TP), in which core disruption extends to the whole core. The joint development of SIMMER-V is of limited scope but aims at significantly expanding the code applicability by providing flexible interfaces to couple a SIMMER-V calculation with other computational domains or other codes, and by adding new advanced physical models such as a detailed fuel pin model and a model of flexible treatment of fuel isotopic composition. The former tasks are conducted by CEA the latter tasks by JAEA. In parallel to the code development, verification and validation of the new models and methods have been performed. This paper describes the objectives and overall framework of SIMMER-V code development program, representative new elements, and recent development progress.