Operations at a Holden Gas Furnace used for uranium recycling at the Y-12 nuclear weapons plant in Tennessee were temporarily delayed because of concerns earlier this spring about the amount of enriched uranium that had accumulated in duct systems associated with the furnace inside the 9212 uranium-processing complex.
The holdup of uranium particles in those ducts reportedly exceeded the nuclear criticality safety limits for fissile materials in that system.
The issues were revealed in a newly released May 23 report by staff of the Defense Nuclear Facilities Safety Board assigned to Y-12.
According to the report, Y-12 contractor Consolidated Nuclear Security discovered the issue while preparing for “production-scale processing” of briquettes containing enriched uranium.
The management team at the facility asked personnel to conduct additional surveys to confirm the amount of “hold-up fissile material” in the furnace’s ventilation exhaust ducts.
Those surveys showed the uranium particulates exceeded the administrative limits for nuclear safety, the report said.
Y-12 spokeswoman Ellen Boatner said the contractor was aware there was some buildup of uranium in the ducts associated with the furnace and other equipment and had monitored them over time.
The safety board report indicated that the ventilation duct tied to the furnace and other operations have uranium holdup from “roughly 50 years of (furnace) operations” and “are not known to have required cleaning to reduce loading” until the recent measurements were taken.
The exact amount of uranium contained in the ducts was not reported.
The DNFSB report said the 9212 shift manager made the decision to suspend operations of the Holden Gas Furnace while various contractor organizations worked “to determine a path forward.” The report noted that maintenance personnel at the facility “cleaned a flame arrester-type filter” to reduce the amount of fissionable material. “But that effort was only partially successful in restoring the system to below (nuclear criticality) limits,” the report stated.
The safety board staff indicated that other measures, near term and long term, were being evaluated to deal with the buildup of materials.
Those efforts apparently were successful, because Boatner on Thursday said the furnace operations had restarted.
Boatner said the holdup of enriched uranium in the ducts was known previously, noting that additional maintenance is being planned during a future outage at the facility.
The furnace is not operated on a continuing basis, but rather as needed to help recover enriched uranium from plant wastes. It has required some significant maintenance and repairs in years past.
Asked for more information about the briquettes, Boatner provided this description: “A briquette is material that has been compacted into a small brick-like shape. It is placed in the furnace as part of the recovery process that captures enriched uranium for reuse.”
