MERCURY IN THE DOE COMPLEX

摘要

A principal function of the Department of Energy and its predecessors during the past 50 years has been the development and production of nuclear weapons. Many of those processes produced hazardous waste and/or mixed waste, which contains both hazardous and radioactive constituents. This legacy waste is currently stored in permitted storage facilities or in shallow land burial sites. Also, high-level waste, resulting from dissolution of spent nuclear fuel contains significant quantities of mercury. Finally, environmental remediation, and decontamination and decommissioning activities will generate additional waste during the next 20 to 30 years. A significant fraction of the waste (both legacy and future) is suspected of containing mercury and other hazardous metals. Most of the waste must be treated in some fashion before final disposal. DOE's treatment processes range from simple stabilization to prevent leaching of hazardous constituents, to complex processes, such as incineration and vitrification. Other facilities will coming on line during the next 5 to 10 years. The fate of mercury in any of these processes is an important consideration. The mercury can end up in the offgas, liquid effluent, or in residuals. The speciation will depend upon the type of treatment used. A high-temperature oxidation process, such as incineration, will tend to produce elemental mercury and mercuric chloride (if there is chlorine in the feed). Low-temperature, aqueous-based processes could produce organic forms of mercury in liquid effluents. While few of the problems with mercury emissions are unique to the DOE, we are unusual in the variety of waste forms and the variety of waste treatment processes being used. One factor is unique to DOE, and complicates the issue considerably; that is the presence of radionuclides. DOE has a policy, known as ALARA, or As Low As Reasonably Achievable, that seeks to limit the exposure to personnel by radionuclides and radioactivity to the lowest reasonable level. This must be a consideration in everything DOE does.