SIMMER-III and SIMMER-IV Safety Code Development for Reactors with Transmutation Capability

The SIMMER-code family has played an outstanding role in the framework and history of mechanistic safety code development for liquid metal cooled reactors with fast neutron spectrum. Its unmatched position is related to the extended simulation range from normal operation conditions, via transients and accidents, core melting and core destruction to in-vessel relocation phenomena and post accident heat removal conditions. SIMMER-III is a two-dimensional (2D), SIMMER-IV a three-dimensional (3D), multi-velocity-field, multi-phase, multi-component, Eulerian, fluid-dynamics code system coupled with a structure model for fuel-pins, hexcans and general structures, and a space-, time- and energy-dependent transport theory neutron dynamics model. An elaborate analytical equation-of-state (EOS) closes the fluid-dynamics conservation equations. The code has originally been developed for the severe accident simulation of sodium cooled fast reactors. However, the general philosophy behind the SIMMER development was to generate a very versatile and flexible tool, applicable for the safety analysis of various reactor types with different neutron spectra and coolants. The multi-physics and multi-scale code family SIMMER is developed in a joint effort of different laboratories, where currently the mai