WASHINGTON (April 27, 2022)—Internal documents released today by the Nuclear Regulatory Commission (NRC) reveal that a senior NRC structural engineer raised serious concerns in 2020 about the earthquake resistance of the NuScale small modular nuclear reactor design. The so-called “Carbon Free” Power Project is planning to build six NuScale 77-megawatt reactors at the Idaho National Laboratory, with the first module coming online in 2029. NuScale received a standard design approval from the NRC in September 2020 for a 50-megawatt version.
However, in a “differing professional opinion” submitted shortly after the NRC granted the standard design approval, Dr. John Ma alleged the design of the building intended to enclose the reactor units and spent fuel pool did not provide assurance that it could withstand a “review-level” earthquake—the largest earthquake considered in the design—without collapsing, and may be vulnerable to smaller earthquakes as well.
Dr. Ma wrote that “collapse of the reactor building … could potentially cause an early and large release of radioactive materials into the atmosphere and ground, which could kill people. Therefore, to ensure that the reactor building will not collapse during the review-level earthquake is important and necessary.” He concluded that “the design of the NuScale reactor building is incomplete, with unknown seismic margin, and is likely unsafe.” Dr. Ma argued that the building should be designed in accordance with standard structural engineering practices for conventional non-nuclear buildings to ensure that it would not collapse during such an earthquake.
Dr. Ma’s dissent was dismissed in April 2021 following a review by an ad hoc panel and NRC management. In a response, Director of Nuclear Reactor Regulation Andrea Veil concluded that for the review-level earthquake, “the Commission’s policy … does not require the staff to verify with 100 percent certainty that the reactor building would not collapse.” Dr. Ma appealed the management decision in June 2021, stating that it was “my professional and civic duty to raise alarm when I see … no proof that [the reactor building] will not collapse during the design-basis earthquake” and that Ms. Veil’s response “collided with the ultimate goal of building design by the structural engineering profession.”
Finally, in February 2022, NRC Executive Director for Operations partially reversed the previous rejection of Dr. Ma’s complaint, concluding that “the basis for accepting NuScale’s stress averaging approach of the reactor building design was not sufficiently documented,” and ordered staff to review the technical approach and evaluate whether there would be any impacts on the standard design approval that the NRC issued to NuScale in September 2020.
“Dr. Ma should be commended for raising these troubling concerns regarding the vulnerability of the NuScale reactor design to earthquakes, and the NRC should be commended for finally taking them seriously,” said Dr. Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists. “The seismic design standards for structures with critical safety functions at nuclear power plants should be stronger, not weaker, than those for conventional buildings. NuScale’s business case is based on its assertion that it is a safer nuclear reactor—now it’s time to prove it by addressing these safety concerns.”
Dr. Ma’s differing professional opinion and subsequent documents can be found here.