Workers suffered exposure to “yellowcake” after an incident at Uranium One USA Inc.’s Irigaray and Christensen Ranch in-situ uranium mine in northeast Wyoming.
That means the U.S. Nuclear Regulatory Commission (NRC) launched a “special investigation” to find out what happened.
Two workers were in the vicinity of a “dryer” containing yellowcake — yellow uranium oxide powder — on Sunday when they heard an alarm and the dryer automatically shut down, the NRC said.
The yellowcake dryer is inside an enclosed building.
“It appears that a seal on the dryer may have broken, causing the yellowcake powder to escape,” the NRC said. “Current information indicates there were no major safety impacts or release to the environment as the dryer is housed inside a pressurized sealed room within a building.”
A NRC inspector traveled to the Wyoming uranium mine to determine whether workers suffered exposure to yellowcake, and to evaluate the operator’s corrective actions already in the works.
It appears the workers were wearing proper protective clothing to avoid exposure to the uranium material, said NRC spokeswoman Lara Uselding. To determine whether there was an exposure, officials will analyze air samples. Also, the workers underwent urinalysis testing.
“We got results back today, and uranium was non-detectable … So they had no intake of uranium,” said Donna Wichers, Uranium One senior vice president of in-situ operations.
Uselding and Wichers said radiation from yellowcake is low enough to be a secondary human health concern compared to ingesting the uranium ore. “Because it’s a heavy metal,” said Wichers. “It would be just like if you ingested lead or any other heavy metal.”
Wichers described the entire incident as a “non-event,” and said the NRC inspector going to visit the mine anyway. She said once the NRC decided to launch a special investigation, part of the agency’s protocol is to issue a press release, “Which we tried to talk them out of,” Wichers said.
The NRC will issue a public report of the investigation within 45 days.
The Irigarary and Christensen Ranch in-situ uranium facilities ceased production in 2000 while reclamation activities continued for several years. The mine changed ownership, and after several years of state and federal permitting, the mine resumed production in January.