Kaiga Atomic Power Station Containment Behaviors During Postulated Severe Accident Along With SAG

摘要

Containment is an ultimate safety barrier which is designed to enclose the whole reactor systems and to prevent the spread of active air-borne fission products. Studies are done to access its performance following severe accident i.e. Loss of Coolant Accident (LOCA) along with failure of Emergency Core Cooling System (ECCS), moderator and calandria vault water cooling system. The accident progression begins with the double ended break in reactor outlet/inlet header with simultaneous failure of ECCS followed by failure of moderator & calandria vault water cooling system. Initially decay heat and metal water reaction energy are assumed to be added to moderator water resulting in boiling of moderator & re-pressurization of containment due to steam addition. Subsequent to moderator boiling, decay heat and metal water reaction energy are assumed to be added to calandria vault water resulting in boiling and re-pressurization of containment due to steam addition. This paper presents the analysis for pressure, temperature, Hydrogen & steam concentration inside the KAIGA containment following the postulated Severe accident. It also includes the assessment of minimum time available for maintaining containment integrity during handling of severe accident involving LOCA with simultaneous failure of ECCS, moderator and calandria vault water cooling systems along with implementation of Severe Accident Guidelines (SAG). By Implementation of SAG i.e. Water addition in Calandria vault would exclude the ex-vessel phenomena. Further, concentration of hydrogen within containment is to be assessed for various types of SAG, so as to find out the potential of hydrogen deflagration/detonation. It is observed that due to boiling of the added water in calandria vault the pressure of the containment would not exceed the design pressure at least for 168 hrs (7 days).