Preliminary study on the postulated siting accident source term of integrated small reactor

Abstract

In accordance with the characteristics of integrated small reactor, a study was conducted on the postulated siting accident source term scheme. The principles for selecting accident types were explored for both the design basis accident condition and the design extension condition. For the deterministic design basis accident condition, a representative accident, such as a fuel handling accident, was identified from the perspective of envelope; for the design extension condition, a representative accident was identified based on the likelihood of accident occurrence, such as when the screening frequency is 10⁻⁷/(reactor·year). When the probability of core damage is extremely low, it is considered to construct at least one entire core fuel cladding damage accident as a representative case. Focusing on the radioactive production, migration, removal, and release, a study was conducted on the source term analysis models and key parameter values of various representative accidents, thus simulating the radioactive activity released into the environment by the accident and identifying ¹³¹I as the dominant nuclide that should be given special attention. Taking a coastal plant site as the object, the dose to the public staying at 16 locations along the site boundary after the accident was further evaluated, and it was demonstrated that even reducing the site boundary to 100 m around the reactor can meet the dose limit requirements of the “small reactor review principle”, and the suitability of the source term schemes was certificated.