The mercury cleanup at the Y-12 nuclear weapons plant in Tennessee could cost up to $3 billion, according to an estimate in a newly released Department of Energy report.
The report, which is dated February 2016, focuses on the technology plans to address the extensive mercury challenges at DOE’s Oak Ridge Reservation and the Savannah River Site in South Carolina.
In the background information on mercury contamination in Oak Ridge, the report says the estimated cost for mercury remediation at Y-12 is between $1 billion and $3 billion. Y-12 used vast amounts of mercury for lithium separation in the 1950s and ‘60s during development of hydrogen bombs, and tons of the toxic metal were released into the environment or otherwise unaccounted for.
“The overarching challenges at Oak Ridge include remediation of the large quantity of residual elemental mercury still present in shallow source zones adjacent to and beneath former mercury use facilities, potential mobilization of mercury during planned deactivation and decommissioning of large mercury-contaminated facilities and associated infrastructure overlying potential mercury sources, potential mobilization of other contaminants, and the persistence and bioaccumulation of methylmercury (the most toxic form of mercury) in the East Fork Poplar Creek watershed despite remediation effort,” the report states.
There are different issues at Savannah River, where mercury has been used for decades as a catalyst in the dissolution of aluminum cladding from irradiated targets in nuclear separation activities and as a “precipitating agent” to remove chlorides. High-level nuclear waste containing significant amounts of mercury is being stored in waste tanks and managed in the liquid waste systems, where there have been higher-than-expected amounts of mercury in the evaporator systems.
There were no cost estimates available on the mercury cleanup-related work at Savannah River, but the two sites are working together to address technologies that may apply to multiple situations and they’re sharing expertise within DOE’s Environmental Management program.
In Oak Ridge, a number of technology plans are already underway, with design in the works for a new $148 million mercury-treatment facility at Y-12. The facility will be located near Outfall 200, where residual mercury in the storm sewer system at the plant continues to leak into the upper stretches of East Fork Poplar Creek. DOE is also looking to locate a research laboratory alongside East Fork Poplar Creek’s lower stretches to conduct field studies on how mercury is transformed in the environment to become methylmercury and to evaluate other mercury-related issues.
The report says mercury contamination “poses a unique, high-priority challenge” to the cleanup mission of DOE’s EM program, particularly at Oak Ridge and Savannah River.
DOE asked for the report to identify mercury-related research and technology development that needs to be done to resolve “key technical uncertainties” in some of the EM mission areas: environmental remediation, facility deactivation and decommissioning, and tank-waste processing.
- Recommendations for the first two areas include:
- Developing rapid screening methods, as well as sensitive, quantitative analyses for mercury in environmental and infrastructure samples.
- Assessing decontamination approaches for D&D.
- Developing in-situ stabilization for mercury-contaminated soil.
- Refining site-specific environmental mercury models.
- Mitigating mercury-in-creek ecosystems through source zone stabilization, water chemistry modification, and ecological management.
Recommendations for research related to tank waste include:
- Improving capabilities for mercury analysis in high-level waste liquids and sludges.
- Developing processes for controlled conversion of mercury from one species to another (between organics, inorganic, and elemental forms).
- Developing mercury sorbents for removing “organomercury” from alkaline waste solutions.
- Pursuing fundamental science to improve understanding of mercury speciation and reaction mechanisms in complex radioactive tank wastes.
