SIMMER-III and SIMMER-IV; Computer codes for LMFR core disruptive accident analysis

Kondo, Satoru; Tobita, Yoshiharu*; Morita, Koji*; Kamiyama, Kenji  ; Yamano, Hidemasa   ; Suzuki, Toru*; Tagami, Hirotaka ; Sogabe, Joji ; Ishida, Shinya  

The SIMMER-III and SIMMER-IV computer codes, developed at the Japan Atomic Energy Agency are the codes with two- and three-dimensional, multi-field, multi-component fluid-dynamics models, coupled with a space- and time-dependent neutron kinetics model. The codes have been used widely for simulating complex phenomena during core-disruptive accidents in liquid-metal fast reactors. Advanced features of the codes in comparison with the former codes include: stable and robust fluid-dynamics algorithm with up to 8 velocity fields, improved representation of structures and multi-phase flow topology, comprehensive treatment of complex heat and mass transfer processes, accurate analytic equations of state, a stable and efficient neutron flux shape solution method and decay heat model. This report describes the models and methods of SIMMER-III and SIMMER-IV. For those individual models, the details of which have been reported elsewhere, only the outlines of the models are presented. The reports of code verification and validation have been already published.