Source Term Evaluation for Advanced Small Modular Reactor Concepts

Abstract

In reactor safety analysis the ‘source term' is the amount of radioactivity available for release to the environment in the event of an accident. Knowledge of the source term is necessary to predict the radiological consequences of a postulated event. In turn, quantification of the source term requires knowledge on the amount of radionuclides present in the reactor and, most importantly, an understanding of the mechanisms in which they may be released to the environment. Mechanistic models have been developed to predict source terms in design basis accident and severe accident analyses of water-cooled reactors. However, several of the SMR concepts proposed for deployment in Canada are more advanced designs that eschew water coolant or even solid fuel. In this study three advanced SMR concepts were examined: a High Temperature Gas Reactor, a Lead-Cooled Fast Reactor, and a Molten Salt Reactor, to determine the mechanisms for radionuclide release and the hypothetical limiting (worst-case) accident with regards to source term for each.