A problem with the criticality alarm system at the nation’s primary storehouse for weapon-grade uranium brought a manager to the scene on a weekend in late April. The situation turned out to be concerning but not threatening.
The incident was revealed in a recently released activity report by Defense Nuclear Facilities Safety Board staff assigned to the Y-12 nuclear weapons plant in Oak Ridge, Tenn.
According to the report, the plant shift superintendent’s office at Y-12 “received an alarm indicating a problem” at the uranium storage facility on Saturday, April 23.
The superintendent contacted the shift manager who was on call for the Highly Enriched Uranium Facility – which was constructed at a cost of about $600 million and loaded with the stocks of fissionable materials around 2010-2011. After arriving at the scene and investigating the situation, the shift manager discovered that a CAAS (Criticality Accident Alarm System) equipment cabinet had experienced a rise in temperature that was higher than the “alarm set point.”
The safety board report said Consolidated Nuclear Security, the government’s managing contractor at Y-12, had planned a number of on-site utility outages for that April weekend. However, the somewhat-reduced ventilation flow in the plant’s high-security uranium storehouse should not have created a problem because “the cooling ventilation for the room with the (alarm system’s equipment cabinet) remained operational,” the report said.
Additional reviews revealed that the temperature switch for the criticality alarm system had been inadvertently set to the same value as the temperature switch for the cabinet’s cooling fan. The DNFSB report also said it should be noted that the equipment cabinet’s cooling fan had been set to activate below what was considered the maximum operating temperature recommended by the vendor.
When asked how the situation was resolved, Y-12 spokeswoman Ellen Boatner said the temperature alarm was reset to the manufacturer’s specifications.
