The government’s revised strategy for the Uranium Processing Facility at the Y-12 nuclear weapons plant depends not only on construction of a cluster of new facilities to process bomb-grade uranium but also leans heavily on extending the life of some existing production buildings — notably 9215 and Beta-2E — to continue their weapons-related roles and also to accept some new missions.
The Defense Nuclear Facilities Safety Board has started taking a close look at those plans and has provided the National Nuclear Security Administration with results of a staff review that draws attention to and analyzes some inherent challenges to keeping these buildings functional and safe — especially under possible earthquake scenarios.
In a cover letter to NNSA Production Manager Steve Erhart, DNFSB Vice Chairman Jessie Roberson noted, “Building 9204-2E (Beta-2E) and the 9215 Complex have known structural performance deficiencies and do not meet modern structural design requirements.
“These deficiencies result in an increased potential for structural collapse and release of radiological material following certain seismic events,” Roberson wrote.
She noted that the NNSA previously had accepted this risk for near-term mission work at Y-12 with the intent to replace Beta-2E and 9215 when the Uranium Processing Facility — initially designed as a single facility to consolidate virtually all of the Oak Ridge plant’s uranium operation — was completed.
“However, following an evaluation of alternative approaches for the UPF project in early 2014, NNSA removed the capabilities of Building 9204-2E and the 9215 Complex from the UPF project scope,” Roberson stated.
The latest DNFSB review of those facilities was designed to get the safety board up to speed on the potential concerns in the future and to provide the NNSA with information as the federal staff reevaluates the facilities “for possible life extension and mission capability additions.”
The report analyzes structural concerns and discusses, in some detail, how those issues are being addressed or might be addressed to deal with the building weaknesses.
Here, for example, is an excerpt regarding ductility issues:
“The designs of the 9215 Complex and Building 9204-2E do not include the ductile design concepts that are used in modern structural design, and thus lack seismic margin to collapse compared to a contemporary structure. This weakness was acknowledged by B&W (the former contractor at Y-12) engineers, who used full elastic demands to qualify non-ductile structural components. Should seismic demands exceed the elastic capacities of certain structural members, undesirable failure modes may be triggered such as column or joint failures that can rapidly lead to progressive collapse.”
In another section dealing directly with Beta-2E, the report stated, “In addition to the potential for structural damage to some concrete columns near the x-ray vault, the review team found that ductile detailing of the 9204-2E facility is lacking, which prevents the structure from adequately performing during large earthquakes beyond the (design basis earthquake).”
In the report’s conclusion, the safety board staff members note again that the NNSA currently plans to extend the life of the two buildings well beyond the time that was originally projected under the original plan for UPF. “In addition, new processing capabilities are being considered for deployment in these existing facilities,” the safety report states.
The remaining operational life of the two buildings is now approaching the life assumed for new designs, and therefore the board staff is recommending that NNSA consider an updated analysis of the buildings using more accurate modeling techniques.
“The current evaluations of the 9215 Complex and Building 9204-2E do not consider the large extension of their operational lifespans and fail to explicitly acknowledge the impact of the lack of structural ductility on each building’s design margin, particularly for the 9215 Complex,” the report stated.
The safety board staff said site personnel at Y-12 stated their intention to reevaluate the risk reviews for the facilities, but that work is not scheduled to be completed until the middle of 2015 — at the earliest, according to the report.
Those risks at 9215 and Beta-2 have gained a look-see on other occasions, even before the change in UPF plans.
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