Results of a Phenomena Identification and Ranking Table (PIRT) Exercise for a Severe Accident in a Small Modular High Temperature Gas-Cooled Reactor

Abstract

Canada has attracted specific interest from developers of non-water-cooled Small Modular Reactor (SMR) technologies, including concepts based on High Temperature Gas-cooled Reactors (HTGRs). It is anticipated that some Research & Development (R&D) will be necessary to support safety analysis and licensing of these reactors in Canada. The Phenomena Identification and Ranking Table (PIRT) process is a formalized method in which a panel of experts identifies which physical phenomena are most relevant to the reactor safety analysis and how well understood these phenomena are. The PIRT process is thus a tool to assess current knowledge levels and/or predictive capabilities of models, thus providing direction to a focused R&D program. This paper summarizes the results of a PIRT process performed by a panel of experts at Canadian Nuclear Laboratories (CNL) for a limiting or “worst-case” accident scenario at a generic HTGR-type SMR. Suggestions are given regarding the highest-priority R&D items to support severe accidents analysis at these reactors.