Savannah River Site facilities and waste disposal are being threatened by heightened levels of mercury found in the site’s H-Area Tank Farm, according to liquid waste contractor Savannah River Remediation (SRR). The entire SRS liquid waste system contains about 60 metric tons of mercury that originated from decades of canyon processing when the material was used to aid in the dissolution of reactor fuel. That amount primarily includes mercury in the liquid waste storage tanks and a minute amount in other facilities. Site officials have historically monitored the mercury due to the threat it poses to humans and the environment, including a potential hazard if it comes in contact with the skin. The potential danger comes from an organic mercury compound, monomethylmercury, which was found during testing conducted by Savannah River National Laboratory. The issue was first observed in May following a system-wide evaluation of mercury levels that began in February.
SRR officials reported last week that while the mercury issue is nothing new, the problem is changing. The company received the green light last year to look for mercury accumulation in the site’s Defense Waste Processing Facility (DWPF). The facility removes all of the water, which includes some mercury, from its waste feed material, but about 43 percent of the material is being recycled back to the water during waste processing rather than being removed. Also, SRR is only able to remove 60 percent of the mercury instead of the intended 75 percent. The issue is extending the amount of time it takes to complete waste remediation and tank grouting, said SRR official Richard Edwards. "We have to have a way to purge it out of the system and collect it," Edwards said.
To combat the issue, the Department of Energy and SRR have already said at least one 55-gallon drum of mercury must be removed from the liquid waste system every year for the remainder of the liquid waste program. SRR will also need to conduct additional sampling to determine concentrations and gain a better understanding of the chemical forms of mercury. So far, more than 40 samples have been analyzed. Other tasks include increased removal of mercury from the evaporators and further studying how the mercury problem will impact site facilities.
The mercury issue may start impacting DWPF canister production because the mercury removal step may take longer. To combat the problem, SRR has chartered a mercury expert advisory panel and has initiated a system-wide evaluation of mercury behavior to determine inventory, processing behavior, and potential impacts of mercury to the liquid waste system, worker safety, and equipment degradation. A long-term action plan for addressing the problem is being developed. In the meantime, conservative actions are being to uphold environmental and worker safety. Based on medical testing results, there has been no mercury exposure to date.
