Assessment of Cesium Compound Behavior during Simultaneous Failure of Reactor Pressure Vessels and Spent Fuel Pools Using Modified ART Mod 2: Fukushima Daiichi Accident Simulation

Abstract

To support the regional strategy development of ASEAN NPSR using scientific research, Modified ART Mod 2 has been used to assess the fission product release from RPVs and SFPs independently. However, the Fukushima Accident suggested the possibility of simultaneous release from RPV and SFP which indicated the necessity of re-evaluation of the maximum source term. The objective was to assess the fission product behavior during a simultaneous failure in RPVs and SFPs of BWR type with Mark I containment design in multiple units using Modified ART Mod 2 in order to evaluate the maximum source term. The releases of cesium compounds in gas and aerosol forms from RPVs and SFPs of Units 1-3 of the Fukushima Daiichi NPP were selected as the case studies. It was found that the behavior of cesium compounds was mainly governed by the aerosols and atmospheric temperatures, which resulted in different characteristics in adsorption and thermophoresis. It also turned out that the simulation of a simultaneous release led to a smaller release than the summation of independent simulations of releases from RPV and SFP by 25%. This study helped estimate the maximum consequences in order to be able to effectively design the EPR for NPP accidents inside or outside the ASEAN region.