CHEYENNE, Wyo. (AP) — Six workers at a Wyoming uranium mine inhaled the radioactive element while cleaning up a spill inside a processing building just days before the mine delivered its first shipment last year, according to the Nuclear Regulatory Commission.
The workers' urine tested positive for uranium at close to seven times the federal agency's permissible level, the federal agency alleges in a Nov. 14 violation notice against Lost Creek LLC ISR, a subsidiary of Littleton, Colorado-based Ur-Energy.
The spill happened Nov. 28, 2013, at the Lost Creek in-situ uranium mine in south-central Wyoming. In-situ mining involves pumping fluids underground to release uranium into a solution that is pumped to the surface. No shafts or tunnels are dug.
Some 1,500 pounds of yellowcake, a precursor of enriched uranium, surged onto the floor of a processing building while a worker was filling a 55-gallon drum with the dry, powdery substance, according to the notice.
Uranium exposure can cause kidney damage. Uranium in the workers' urine afterward tested between 24 and 102.5 micrograms per liter; the NRC limit is 15.
The employees involved in the cleanup had no ill effects, and their exposure remained well below the maximum allowable annual limit, Ur-Energy President Wayne Heili said Friday.
He said he believed the workers were wearing respirators at the time.
The NRC cited the company for failing to issue a radiation work permit for cleaning up yellowcake. The radiation safety officer who would have done so took part in the cleanup, Heili said.
"He didn't stop to do some required paperwork," said Heili, who noted the violation notice was not for the spill or worker exposure.
None of the yellowcake escaped the building, he said, and the company has taken steps to prevent another spill.
The alleged violation ranked in the least severe of the NRC's four categories of violations.
The Wyoming workplace safety enforcement office wasn't aware of the accident but contacted Ur-Energy about it following a reporter's inquiry, Wyoming Department of Workforce Services spokeswoman Hayley McKee said Friday.
As of Friday, the NRC had not received a response from Ur-Energy that would be publicly available, agency spokeswoman Maureen Conley said. She declined further comment.
Heili said Ur-Energy would file a response to the NRC.
Lost Creek is among Wyoming's newest in-situ uranium mines. Production began in August 2013, and the mine's first yellowcake shipped within a week after the spill.
Wyoming produced 54 percent of the more than 5 million pounds of yellowcake produced nationwide last year, according to the Wyoming State Geological Survey.