The Savannah River Site's liquid-waste contractor inadvertently transferred 6,600 gallons of high-level liquid tank waste into the incorrect tank because of degrading infrastructure, according to the Department of Energy.
In addition, the contractor also noticed a higher-than-expected level of mercury in the tank waste salt streams at SRS. There were no reported exposures to workers or injuries as a result of the incidents.
Both incidents were reported by Savannah River Remediation, the contractor, to the Energy Department.
The contractor on March 11 and 25 transferred the waste to a tank containing similar waste, but not the designated tank. On both occasions, transfers were ongoing from Tank 37 to Tank 23, and both times some of the waste instead transferred to Tank 32.
The first incident occurred when a degraded valve actuator did not fully close because of a malfunction, officials wrote. The failure made a position indicator unreliable, officials wrote. After the failed actuator was eliminated and the valve successfully closed, the waste transfer valve failed again because of a degraded valve seat, which is inside the valve, and allowed waste to slip through.
Corrective actions are ongoing and include flushing the drain lines in the area of the valve and better understanding the failure modes and replacing degraded valves and seven other valves.
"Waste transfers that have been leak checked and/or have double-valve isolation are back in service. All other transfers require facility management approval prior to being performed," the Energy Department wrote in an email.
With the mercury issue, the Department reported that no disposal permit limits have been exceeded; however, levels were higher than internal safety controls allow, resulting in SRR conducting a system-wide evaluation of mercury in February.
Tests conducted by the Savannah River National Laboratory showed unexpected trace levels of an organic mercury compound, monomethyl mercury. The compound is a potential worker hazard if it comes in contact with the skin, leading the site to take further action.
"While standard personnel protection clothing worn in radiological areas provides an adequate level of protection, workers are now required to wear nitrile gloves for added protection," the Energy Department wrote.
Based on work practices and results from prior medical testing of SRR employees, there is no indication of mercury exposure. Voluntary medical testing, however, is being offered to workers.
Derrek Asberry is the SRS reporter for the Aiken Standard.