Water and U-235 don’t mix really well without uncomfortably critical results, and that’s why casting operations with bomb-grade uranium were shut down for a brief period last month at the Y-12 nuclear weapons plant.
According to a report by staff of the Defense Nuclear Facilities Board, the casting operations in Y-12’s 9212 complex were “paused” last month because of a perceived “deficiency” in nuclear criticality safety.
The issue was reportedly in the area around Stack 110, which is the primary ventilation system that supports uranium casting operations in Building 9212.
Uranium casting is an important function at Y-12, of course, involving the melting of uranium to form shapes for multiple purposes — ranging from weapons components to cylinders or buttons for shipment and storage.
The newly released report by the DNFSB staff for the week of Jan. 8 said that nuclear criticality safety engineers documented a safety deficiency after production personnel reported that about 2 feet of water had been found in the “discharge tube” below Stack 110’s dust collector.
The discharge tube, which collects uranium dust that falls from the stack filters, reportedly has a geometry that is nuclear criticality safe.
“However, the criticality safety evaluation for the Stack 110 system requires the dust collector to limit water ingress such that water cannot accumulate to the cartridge filter housings above the discharge tubes,” the safety board report stated.
In this situation, the water level apparently did not approach the filter housings, but the DNFSB report noted that it still represented an “off-normal condition” that necessitated nuclear criticality safety guidance “on the actions to be taken for recovery.”
Casting operations inside 9212 were reportedly paused while the nuclear safety and systems engineers determined the location where water was entering the tubes and developed actions for recovery.
Y-12 spokeswoman Ellen Boatner said the operations were only suspended for a “brief time” while the situation was investigated. They have resumed since then, she said.
Boatner said the water did not pose a safety issue, “but was considered an unusual condition.”
The spokeswoman further noted, “Additional efforts have been made to protect the tube from precipitation.”
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