It seems there’s been a recent trend of problems at Stack 110, a key emissions point in the old uranium-processing complex known as Building 9212. Significant improvements were made at the site a few years ago, combining two emission stacks as part of a risk-reduction program. But issues seem to keep cropping up there.
Early this year, casting operations with enriched uranium were paused at 9212 because a couple of feet of water had collected in a “discharge tube” below Stack 110’s dust collector. That raised questions about criticality safety that warranted a closer look.
More recently, according to a March 28 report by staff of the Defense Nuclear Facilities Safety Board, it was noted that particles of enriched uranium were collecting at a faster-than-expected rate in the filters associated with Stack 110.
Non-destructive measurements of the filters showed the accelerated loading of fissile material.
“These filters collect dust from the ventilation of the vacuum induction melt furnaces and other E-wing operations and were part of the upgrades that replaced the bag filter house in December 2013,” the weekly activity report stated.
“The system has backflow and internal air pulse features to remove built-up dust on the filters; however, this feature has not provided the expected reduction in filter loading since its installation,” the safety board staffers wrote.
The measurements are conducted on a periodic basis to “ensure nuclear criticality safety and security loading limits are not exceeded with the security limit being more restrictive,” the staff report said.
The report said engineers with Consolidated Nuclear Security, the government’s managing contractor at Y-12, had increased the frequency of measurements to more closely assess the loading of uranium dust.
The contractor also ordered replacement filters “in anticipation of the need to replace the filters in a few months.”
The CNS engineering group also is working with the manufacturer to come up with filters that will improve the “backflow feature” that is supposed to remove uranium dust if there’s a buildup on the filters.
It’s not yet clear if a new type of filter has since been installed there.
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