March 17, 2014

DNFSB RAISES DESIGN CONCERNS ON UPF

By ExchangeMonitor

The Defense Nuclear Facilities Safety Board wants the National Nuclear Security Administration to take a closer look at modeling assumptions underlying design of the Uranium Processing Facility. In a Sept. 6 letter to NNSA Administrator Tom D’Agostino, DNFSB Chairman Peter Winokur suggested that the NNSA hadn’t “validated’ some modeling assumptions that were used in the design of the facility. “These assumptions may conceal localized issues with the structural design such as the inability of the structure to support safety-related controls,” Winokur wrote. “The ability of safety-related controls to function after a seismic event is necessary to maintain worker safety. The Board believes that justification of these assumptions is necessary to understand adequately the UPF structure’s behavior in the event of an earthquake and ensure that the potential to damage safety-related controls is not overlooked or incorrectly represented.” The Board requested a report on the NNSA’s plans to address its concerns in 60 days.

The Board has largely approved of the overall structural design efforts on UPF, noting that it was adequate earlier this year. But the Board said the NNSA’s current plans do not adequately explain the agency’s technical approach or justify the modeling and design techniques utilized. Those assumptions include work on wall openings, wall element tie-ins, section cuts in the foundation, and simplified calculations used in the main structural analysis of the building. “At this stage in the design process, the project team should verify the adequacy of safety structures, systems and components, ensuring that each will maintain its integrity during design basis events and fulfill its safety function,” the Board said. “In this case, all modeling assumptions … should be technically justified before the final design is completed. Doing this now will also minimize any potential impact on the project should design changes be required if an existing assumption proves to be unjustified.”

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