Modeling and Simulation of Caiser for CANDU Accident Progression

Abstract

Since the legislation for the severe accident management has specified the criterion for the fission product release in the severe accident condition, such as Cs-137 < 100TBq, the accurate severe accident calculation, together with the calculation tool, become to be absolutely necessary. Hence, Korea has been developing a new integrated severe accident code, which is called CAISER (Candu Advanced Integrated SEveRe code) in order to support the regulatory body in reviewing the accident management plan (AMP) which is submitted by the nuclear industry. The core degradation phenomena in a fuel channel, which is treated in CAISER, includes all kinds of heat transfer, steam-Zr oxidation, a fuel rod slumping, melting & relocation of main components and thermal interaction of relocated mass with pressure tube. The possibility for the melting & relocation of fuel rod in a fuel channel, which lead to the local failure of pressure tube by the molten corium in a fuel channel is evaluated. And, the main phenomena in a calandria tank treated in CAISER include all kinds of heat transfer, sagging of a fuel channel, debris bed formation caused by a fuel channel failure, the molten pool formation and the calandria tank wall failure, which is modeled with the ablation of wall by molten corium, creep rupture failure mechanism. The governing equations for the main components in a fuel channel and in a calandria tank has been established. For the purpose of code validation, CS28-2 experiment is compared with that of CAISER calculation, especially for the temperature of fuel rods in a different ring number.