Development of severe accident integrated analysis code, SPECTRA for sodium-cooled fast reactors

Uchibori, Akihiro ; Sonehara, Masateru ; Aoyagi, Mitsuhiro ; Kawada, Kenichi   ; Takata, Takashi  ; Ohshima, Hiroyuki

A computational code, SPECTRA was developed for integrated analysis of in- and ex-vessel phenomena during severe accidents in sodium-cooled fast reactors. SPECTRA consists of in- and ex-vessel modules which have a thermal hydraulics module as a base part. The in-vessel thermal hydraulics module computes complicated multi-dimensional behavior of liquid sodium and gas by using the multi-fluid model considering compressibility. Relocation of a molten core is computed by the dissipative particle dynamics method. A lumped mass model was employed for computation of ex-vessel multi-component gas flow including aerosols. Analytical models for sodium fire, sodium-concrete interaction, and debris-concrete interaction were integrated into the ex-vessel module. Basic capability of SPECTRA was demonstrated through analysis of a loss of reactor level event of a loss of reactor level event.