The Canada-based reactor developer said the review was part of a cross-border regulatory programme which was set up in 2019 between the Canadian Nuclear Safety Commission (CNSC) and the US Nuclear Regulatory Commission (NRC).
The two agencies jointly reviewed Terrestrial Energy’s postulated initiating events (PIE) analysis and methodology for their proposed IMSR design, a move which the company said was “foundational” for further regulatory safety reviews and licence application preparations.
According to the International Atomic Energy Agency (IAEA), PIEs are the starting point for any deterministic safety analysis and relate to events “of very low frequency or consequences” including equipment failure, human errors and external events, both natural and made-made.
Terrestrial Energy, established in 2013, is proposing to build its Generation IV IMSR plants for customers throughout North America by the late 2020s or early 2030s. According to Canadian Nuclear Laboratories, a 190-MW IMSR is one of four projects in an invitation process to host Canada's first small modular reactor.*
The IMSR plant operates at high temperatures (600-700 degrees Celsius) and is said to be 50% more efficient than traditional reactors. It uses a graphite moderator and standard assay low-enriched uranium fuel with the same level of enrichment (less than 5% U-235) as in conventional nuclear plants.
In addition, using a molten salt fuel and coolant allows the IMSR to incorporate to the greatest extent possible the virtues of inherent and passive safety for reactor operation.
In December 2019 the CNSC and the US NRC chose the IMSR for the first joint technical review of an advanced, non-light-water nuclear reactor technology.
Terrestrial Energy quoted former CNSC president Michael Binder as saying that the recent review was “clear evidence” that international regulatory harmonisation is possible.
International collaboration is seen as essential to ensuring a harmonised approach is taken as the nuclear industry and policymakers prepare for the rollout of new technologies such as SMRs. The IAEA is working on the establishment of a technology-neutral framework for safety to help harmonise international approaches to new-generation reactors.
*The article was updated on 9 June 2022 to reflect better the current state of Terrestrial Energy's IMSR projects in North America.
