Study on the migration and release of fission products under severe accident for PWR

A large number of radioactive fission products are released into the environment and cause harm to the human directly in the case of severe accidents. In this paper, the MELCOR program was used to study the existence form of CsI in the primary coolant system and containment, as well as the migration and release behavior of CsI and inert gas to the containment and environment. The results showed that CsI was mainly released in the form of aerosol. Most of the CsI retaining in the primary coolant system was deposited on the heat structures. About 70% of the CsI migrated into the containment in the form of aerosols and continuously deposited in the containment or dissolved in the water, a small amount of CsI released to the environment. Most of the inert gas migrated into the containment after the accident and only a small portion remained in other reactor systems. Only 0.11% of inert gas released to the environment under normal containment leakage rate. (authors)