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DOE SAYS ALTERNATE ANALYSIS OF PF-4 SEISMIC RISKS WILL BE DONE IN DEC.
The National Nuclear Security Administration is expected to complete an alternate analysis of seismic risks at Los Alamos National Laboratory’s Plutonium Facility by mid-December, Deputy Energy Secretary Dan Poneman said in a letter to the Defense Nuclear Facilities Safety Board this week. The NNSA has poured millions into upgrading the facility against a massive earthquake, which is believed to potentially occur every 2,000 years in Northern New Mexico, and NNSA’s own calculations have lowered the total effective dose equivalent to 23 rem, just under the 25 rem DOE guideline.
The DNFSB, however, has pressed the agency to take a new look at the modeling techniques used to gauge the risk of a collapse at the facility, and Poneman said a “modal loading analysis” would be completed by Dec. 16. He noted that a “dynamic linear analysis” and a “static nonlinear pushover analysis” had already been completed. “NNSA believes this alternate analysis will be helpful in understanding further the seismic integrity of the PF-4 facility and providing assurance that all of its structural elements that require updating are identified,” Poneman wrote in his Sept. 3 letter to DNFSB Chairman Peter Winokur, which was released by the Board this week.
Study to Have Significant Impact
While the NNSA has suggested the facility meets guidelines for protecting the public from an exposure, the Board said last year that the lab was not conservative enough in its calculations and that its own analysis revealed the potential exposure to be more than four times the 23 rem total effective dose equivalent estimated in the lab’s analysis. The ongoing review could have a significant impact on the future of the Plutonium Facility, how much seismic strengthening is necessary and how much it might cost.
At issue is whether the facility might collapse in the event of a massive earthquake, an issue that previous studies have ruled out but one about which the Board remains concerned. That concern is centered on round columns that support the facility and informed by the 1989 Loma Prieta earthquake that collapsed elevated highways in the San Francisco Bay Area. In public comments at a Capitol Hill Club event this summer, DNFSB member Jack Mansfield explained the Board’s concerns. The facility, built in the late 1970s, is “brittle,” Mansfield said. “It was discovered after this facility was built that large buildings, to be survivable in serious earthquakes, have to have a bit of ductility. It was also discovered after the Loma Prieta earthquake that round columns, if accelerated up into the plywood they support, crumble. Those two vulnerabilities were identified early, but they’re not built into PF-4.”
He added: “The result is that there is a probability, albeit small, that the building could collapse, with great loss of life within and with dispersal of plutonium.” Previous upgrades were based on calculations that did not fully characterize the problems facing the facility, Mansfield said. Those calculations were “very good” and “did a lot,” Mansfield said, but “the problem is that any of the columns, crushed like the ones on the highway did—the whole roof would go down like a zipper.”
Some Repairs Underway
In recent years, structural upgrades involving a new roof beam were completed, and the lab has repaired three mezzanine areas, reinforced ceilings with steel and conducted further analysis on roof joints to reduce the impact of a massive earthquake. More work is ongoing, and the NNSA requested $30.7 million in Fiscal Year 2014 for the $99 million TA-55 Reinvestment Project-Phase 2, which includes the replacement and refurbishment of glovebox stands to meet seismic standards. The new analysis could mean more money is needed for more upgrades to the facility, which serves as the center of plutonium work in the nation.
In his Sept. 3 letter, Poneman slightly hedged on the completion date of the analysis, suggesting that the date could slip. “NNSA recognizes that there may be some challenges to maintaining the schedule due to the developmental nature of the work and the potential need to implement changes due to the independent review process,” he wrote. “If the schedule changes for any reason, NNSA will promptly communicate that to the DNFSB.” —Todd Jacobson