PF-4 quake analysis continues

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DNFSB > DOE officials promise seismic reports by year’s end

By The Staff

The Department of Energy this week updated the Defense Nuclear Facilities Safety board on its schedule for completion of the Los Alamos National Laboratory Plutonium Facility (PF-4) Alternate Seismic Analysis.

Deputy Energy Secretary Dan Poneman, in a letter to DNFSB chair Peter Winokur said the NNSA has completed two major analysis efforts, a dynamic linear analysis and a static nonlinear pushover analysis.

“In my September 28, 2012, letter to the Defense Nuclear Facilities Safety Board (DNFSB), I committed NNSA to conducting a modal loading analysis, the alternate analysis, of the PF-4 facility to augment the previous analyses. 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.
Poneman’s letter indicated the timetable for completion of the upgrades would be in by December although he gave some wiggle room on the schedule.

“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. If the schedule changes for any reason, NNSA will promptly communicate that to the DNFSB,” Poneman wrote.

This is the plan the NNSA submitted to the DNFSB in regard to PF-4.
• Review documents and prior analysis
•Identify structural components and key parameters
• Prepare analysis and evaluation criteria
• Characterize structural component behavior and establish component-level analysis procedures
• Perform individual component non-pushover analyses, and develop and validate component-level models for pushover
• Validate the adaptive nonlinear modal pushover analysis methodology
• Develop modal pushover model and perform UB and LB, and sensitivity study cases to failure
• Identify structural elements requiring upgrades to meet PC-3 requirements and recommend modifications.
• Perform fragility analyses. Present results, incorporate reviewer’s comments, and finalize the report.

The structural upgrades come on the heels of seismic concerns brought up by DNFSB, watchdog groups and other agencies.

There is concern PF-4 may collapse in the event of a major earthquake.

The Nuclear Weapons and Materials Monitor reported the concern is centered on round columns that support the facility.

Similar round columns collapsed elevated highways in San Francisco during the 1989 earthquake.

The trade publication quoted DNFSB member Jack Mansfield, who detailed the board’s concerns.

The facility, built in the late 1970s, is “brittle,” Mansfield told the trade publication. “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.”

The trade publication reported that 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.”