Sensitivity Analysis on Key Parameters of Severe Accident Source Term of PWR

Abstract

The complicated severe accident phenomena in typical Pressurized Water Reactor (PWR) Generation III may have a strong influence on source term release into environment and radiological consequence. The study on sensitivity analysis is beneficial to the identification of important factors in severe accident source term analysis and the quantification of their impact. ASTEC, the integral code of severe accident analysis developed by IRSN, is used to analyze the sensitivity of key parameters of severe accident source term for typical PWR Generation III, with the simulation of safety systems and source term phenomena, in the representative sequence with fast accident progression, Large Break Loss of Coolant Accident (LBLOCA). With the consideration of the design features of typical PWR Generation III and research status of severe accident source term, the key parameters for sensitivity analysis are identified and selected based on the whole process of radionuclides release, including gaseous iodine mass release fraction from primary circuit to containment, silver iodide reaction, dose rate and pH value in sump, washing effect, etc. The sensitivity is quantified by iodine release mass to containment, which is one of the most dangerous radionuclides due to its threat to environment and human thyroid after inhalation and ingestion. The gaseous iodine mass release fraction from primary circuit to containment, silver iodide reaction and washing effect are presented in results as the major contributors to the variation of severe accident source term evaluation.