Following a review by the Advisory Committee on Reactor Safeguards (ACRS), US Nuclear Regulatory Commission (NRC) staff have agreed that the commission's final safety evaluation report for NuScale's small modular reactor (SMR) should be issued. Issuance of that report with no open items will complete NRC's technical review of the reactor design. 

NuScale's SMR design features a fully fabricated power module based on pressurised light water reactor technology. Each module can generate up to 60 MWe, and the scalable design can be used in power plants of up to 12 individual modules. It is the first - and so far only - SMR to undergo a design certification review by the NRC.

The NRC's design certification process is based on a review by NRC staff of the application, which addresses the various safety issues associated with the proposed nuclear power plant design, independent of a specific site. In granting a design certification, the regulator approves a nuclear power plant design, independent of an application to construct or operate a plant. A design certification is valid for 15 years from the date of issuance, but can be renewed for a further 10 to 15 years. The final safety evaluation report (SER) with no open items is sixth and final phase of the NRC's generic design certification review for the NuScale design. The final SER is scheduled for completion next month.

The ACRS - an independent advisor to the NRC that reviews and reports on safety studies and reactor facility licence and licence renewal applications - told NRC Chairman Kristine Svinicki in a 29 July letter that the final SER for the NuScale design should be issued. In its review of the SER, the ACRS concluded "there is reasonable assurance that [the NuScale SMR] can be constructed and operated without undue risk to the health and safety of the public". However, it identified "several potentially risk-significant items that are not completed at this time".

"We request the opportunity to review the qualification of emergency core cooling system valve performance, the identification of a successful recovery strategy to prevent potential reactivity insertion accidents associated with boron dilution sequences, and the updated probabilistic risk assessment," the ACRS told the NRC. In a 25 August letter to ACRS Chairman Matthew Sunseri, Margaret Doane, NRC Executive Director for Operations, said staff "acknowledges the ACRS request".

Doane told Sunseri that NRC staff agree with ACRS's conclusion that a design certification and standard design approval for the NuScale applications should be issued, "subject to the staff's proposed exclusions regarding the finality of design requirements: shield wall design, containment leakage from combustible gas monitoring, and steam generator tube structural and leakage integrity". She added that NRC staff "anticipates additional information will be available on these topics as part of a future licence application that will reference the NuScale small modular reactor design."

Doane added, "The Committee's novel review approach, which focused more on critical issues, significantly complemented the staff's efforts to ensure that its review was appropriately risk informed, efficient and thorough."

NuScale's first customer, Utah Associated Municipal Power Systems (UAMPS), is planning a 12-module SMR plant at a site at the Idaho National Laboratory. Construction is scheduled to start in 2023, with the first module expected to begin operation in 2026. However, according to a 24 August report by the Washington Examiner, UAMPS has informed NuScale it has needed to push back the timeline for when it plans to operate the first module from 2026 to 2029. Citing a rise in expected costs, completion of the 12-module plant would be delayed from 2027 to 2030. At an 18 August meeting, the municipal council of the City of Logan, a member of UAMPS, voted to leave the project due to the increasing costs.

Researched and written by World Nuclear News