The NRC accepted NuScale’s SMR design certification application back in March 2018 and issued its final technical review in August 2020. Later, the NRC voted to certify their 50 MWe design on July 29, 2022, making it the first SMR approved by the NRC for use in the United States. In 2023, the NRC officially certified their design, making it the first and only SMR to achieve either milestone.

Now NuScale is seeking approval of their VOYGR-6 plant design which features an uprated power rating from 50 MWe to 77 MWe. Their application has been docketed after the NRC began technical review of their March 2023 application. The uprated design, under review, includes the same fundamental safety case the NRC approved in 2020. NuScale is somewhat confident that their uprated design will be approved. They have requested the NRC provide a 24-month review schedule for the approval process, aligning their timing needs for their U.S. customers.

The power ratings for small modular reactors seem to have migrated toward the IAEA SMR design threshold of three hundred Mwe. This is evidenced by the rollout of the BWRX-300 (boiling water reactor with significant commitments from Ontario Power Generation and the Tennessee Valley Authority) and the AP300 MW SMR design from Westinghouse. Economies of scale in sourcing components, manufacturing, and operational efficiencies for customers seem to have converged on this level of electrical power generation.

Also, NuScale’s ‘six-pack’ power package (462 MWe) compares closely with the Rolls-Royce 470 MWe mid-range PWR. It is now being reviewed by the UK Office of Nuclear Regulation as part of their agency’s generic design assessment. In the UK, Rolls-Royce is touting their mid-range 470 MW PWR as an SMR, but it significantly exceeds the IAEA standard of three hundred MWe.

Looking at the advanced reactor category, X-Energy has an agreement to build four 80 MW HTGRs (hot temperature gas reactors) for Dow to provide process heat at a Texas chemical plant (320 MW). And TerraPower’s Natrium sodium cooled design, intended to replace coal-fired power plants for electricity generation, comes in at 345 MW.

In Canada and the UK, Moltex is developing a 300 MW molten salt reactor for power generation and process heat applications. Also, in Canada, Terrestrial Energy plans to offer customer their 195 MW molten salt reactor in pairs for a total of 390 MW.

The reactor developers claim their designs are modular and transportable. The modules, when fabricated by the vendor or its suppliers, will be transported by truck, rail, or barge to the reactor site where they will be assembled into a finished nuclear power plant. A similar fabrication was accomplished at Plant Vogtle for the construction of two Westinghouse AP1000 reactors.

NuScale’s first customer, UAMPS (Utah Associated Municipal Power Systems) is inside the Idaho National Laboratory boundary, on the Arco desert, fifty miles due west of Idaho Falls, ID. There is a rail connection via a Union Pacific spur. However, it does not terminate near the UAMPS site. Therefore, additional trackage is necessary to offload and deliver from the spur to the site by truck.

All the 300 MW range SMRs will face similar challenges in getting their components delivered to customer sites. For truck travel, the oversize loads will need to be able to fit beneath the clearances of both major highway and rural road overpasses. Another factor is bridge load ratings for the combined weight of the truck, trailer, and its load.

Undoubtedly, all the SMR vendors are working with the issue of transportation logistics in anticipation of making decisions on how many pieces of the reactor need to be shipped in separate loads.