Development of TH-Pre-PIRT for Micro Gas-Cooled Reactors

Abstract

Vendors of several small modular reactor (SMR) technologies, including non-water-cooled and water-cooled reactor concepts, have engaged the Canadian nuclear regulator for vendor design reviews. SMR concepts, especially the non-water-cooled ones, differ in the design compared to the current reactor fleet: they usually feature advanced fuel, passive safety, and autonomous operation. Development of thermalhydraulic preliminary phenomena identification and ranking table (TH-Pre-PIRT) is being undertaken at Canadian Nuclear Laboratories (CNL) for a micro gas-cooled reactor (GCR) concept. Most of the previous PIRTs for GCRs were undertaken for Very High Temperature Reactors, and some of those PIRTs are proprietary. Therefore, there is a need for TH-Pre-PIRT analyses at CNL to help achieve the micro modular reactor’s deployment in Canada as envisioned in CNL’s Vision 2030. The terminology TH-Pre-PIRT is adopted here as the concept considered in this study is a “manufactured test problem”, has not been deployed and is currently at the conceptual stage. The objective of the TH-Pre-PIRT is to identify the selected postulated design basis accident scenarios to determine the readiness of computer codes and identify the associated gaps within the modelling tools for development needs. The TH-Pre-PIRT team used the well-established nine-step process to identify the phenomena, rank their importance and the knowledge level and provide a rationale for the associated ratings. The scenarios and the importance ranking derived from the current effort at CNL will eventually need to be repeated upon the deployment of a test reactor.