A three-dimensional neutronics-thermohydraulics simulation of core disruptive accident in sodium-cooled fast reactor

The SIMMER-III code is a two-dimensional, multi-velocity-field, multi-phase, multi-component, Eulerian, fluid-dynamics code coupled with a fuel-pin model and a space- and energy-dependent neutron transport kinetics model. Since the three-dimensional representation of the core enables realistic distribution of the materials constituting the core, including control rods, SIMMER-IV has been developed as a direct extension of SIMMER-III to three dimensions with retaining exactly the same physical models as SIMMER-III. Recently, the parallelization of SIMMER-IV has been achieved, allowing application to reactor calculations within available computational resources. A three-dimensional simulation using SIMMER-IV has drawn more realistic accident scenario including a late stage during the transition phase. Additional static neutronic calculations identified major factors significantly influencing the reactivity change shown in the SIMMER-IV simulation.