The U.S. Nuclear Regulatory Commission said this week it would not penalize Holtec International for two violations of federal regulations during an update to the design of a spent nuclear fuel storage cask.
The Camden, N.J., energy technology company could have incurred a $36,250 fine for one safety violation, NRC Office of Enforcement Director George Wilson wrote in an April 24 notice of violation to Holtec President and CEO Kris Singh. “However, the staff determined … that a civil penalty for Violation 1 was not warranted. This determination is in recognition of no aggravating circumstances, Holtec’s prompt and comprehensive correction of the violation, and the absence of recent escalated enforcement action.”
The other violation did not rise to the level of escalated enforcement, according to Wilson.
The NRC initated its inspection of the issue in May 2018, beginning with a five-day site visit to Holtec headquarters.
The inspection was linked to a March 2018 incident in which a 4-inch steel pin was found loose at the bottom of a Holtec storage canister that was to be filled with spent reactor fuel being transferred from wet to dry storage at the San Onofre Nuclear Generating Station (SONGS) in San Diego County, Calif. The pins are components of shims that support fuel baskets and aid airflow within the container.
Holtec subsequently switched to a different canister design to continue the fuel transfer at the retired nuclear power plant. That operation has been on hold since an August 2018 mishap in placing a canister into its storage slot near the Pacific Ocean.
The industry regulator’s inspection produced a Nov. 29 report citing two seeming breaches of federal nuclear quality assurance regulations: First, Holtec did not provide sufficient safety-related design control methods in updating the shim to the use pin design in 2016; second, it did not keep written records of updates to the canister design, including specifying why the revision did not require the NRC to approve an amendment to the canister’s certificate of compliance.
Holtec and NRC officials met on Jan. 9 for a pre-decisional conference (PEC) that allowed the company to further make its case against being penalized ahead of the final ruling. At that meeting, representatives from the agency and company played down any safety threat from the incident.
Nonetheless, “The NRC has determined that two violations of regulatory requirements occurred,” Wilson wrote. “This determination was based on information developed during the NRC inspection, information you provided in your responses to the inspection report, and information you provided during and after the PEC.”
The design control breach was “potentially safety significant,” the NRC official added. The possible failure of more than one shim pin in a canister loaded to full design-basis heat load configuration could have undermined the vessel’s heat-transfer characteristics, according to Wilson. “This could have resulted in an increase in the peak cladding temperature beyond the allowable limit and potentially damage the fuel cladding.”
However, he noted that the canister was not loaded to the design-basis level. A Holtec thermal analysis also determined that even the failure of multiple shims would not exceed safety margins. Agency staff found, after evaluating the Holtec analysis, that the loaded canisters would remain safe for their licensed storage period.
While the violation did not create a real-life safety concern, Holtec’s failure to fully evaluate a potential exposure event represents a Severity Level III breach, Wilson stated.
The company received corrective action credit for taking a series of short- and long-term steps to correct the problem, including conducting a root-cause evaluation; assessing other loaded canisters of the same design to ensure they were safe; alerting customers that had the same canister design loaded with used fuel; and doing a lessons-learned analysis.
The same canister design is reportedly used at the retired Vermont Yankee nuclear power plant and other sites.
While this violation did not result in a fine, it could be used in determining penalties in future violation cases, Wilson stated. Holtec could also face a heightened inspection program by the NRC.
The second violation was designated as Severity Level IV, which does not come with any financial penalty.
Holtec on Friday did not respond by deadline to a query regarding the NRC decision.
