The Nuclear Regulatory Commission revealed the incident in a new report to Congress published Friday in the Federal Register.
“Criticality,” or a sustained nuclear chain reaction that releases radiation, was possible as the uranium pooled in both the box and the elevator pit, the NRC said.
“If a criticality accident had occurred in the filtered glovebox or the elevator pit, it is likely that at least one worker would have received an exposure high enough to cause acute health effects or death,” the NRC report said.
NFS, which makes fuel for the Navy at its plant here, was not fined, but NRC spokesman David McIntyre said NFS has to change where its operations are configured, and it has agreed to undertake a safety conscious workplace environmental assessment.
Company Chief Executive Officer Dwight Ferguson said NFS agreed to the measures. He said employees have already undergone extensive training because of last year’s strike by the NFS union.
“No employee was injured during the spill, and no employee was found to have received excessive radiation exposure,” NFS spokesman Tony Treadway said in a statement. “No adverse impact to the general public or the environment resulted from this matter. The issue was resolved through a significant investment in personnel, redundant safety measures and consultation with a variety of nuclear safety experts.”
The incident might never have been disclosed publicly if not for laws requiring the NRC to annually report “abnormal occurrences” of its license-holders to Congress.
The document said NFS planned to move an unused filter glovebox. Workers opened and drained the filters but did not reseal the system tightly afterward. When HEU was next sent through the line, the substance leaked into the glovebox.
According to Ferguson, the glovebox, which had never been put into service, had drains in it but was not approved for use.
“On several occasions before the event, workers had reported signs of a yellowish liquid in the filter glovebox,” the report said.
“Supervisors had failed to fully investigate the reports because they assumed the yellowish liquid was natural uranium solution which had been used to initially test the process.”
Ferguson called the incident an oversight. He said he would classify this incident as more of a spill than NFS normally would have.
This leak could have caused a criticality because of the glovebox’s size and shape and lack of controls to prevent the solution from accumulating.
According to the report, the solution leaked through uncontrolled drains to the floor. McIntyre said the problem was there was a dumbwaiter in that area with a pit underneath where the solution might have gone and caused a criticality. Ferguson said the company mopped up the substance with cheesecloth and made certain it was disposed of “in a safe geometry.”
Ferguson said NFS reported the incident and has not had any more spills of that size since.