Like the United Kingdom, the United States has accumulated a nuclear legacy from over 60 years of research, production, use and storage of nuclear mate­rials. Over this time frame, nuclear material was produced for use in both civilian power plants and in military weapons. The Department of Energy (DOE)’s 120 sites contain 40 million cubic meters of contaminated soil and debris and 1.7 trillion gallons of contaminated groundwater. Of this, at least 50% is contaminated with radionuclides, including caesium-137, plutonium — 239, strontium-90, technetium-99, uranium-238, and uranium-235, as well as heavy metal contamination including chromium, lead and mercury.23 The associated cleanup cost has been estimated to be in excess of a trillion dollars.24 Contaminated sites include former uranium ore processing facilities such as Rifle, Colorado and Moab, Utah. The clean-up of these sites was tasked to the DOE under the Uranium Mill Tailings Remedial Action (UMTRA). During the years of operation of the Moab site, approximately 10.5 million tons of tailings and contaminated soils accumulated in an unlined pile 750 feet from the Colorado River.25 In 2005, the DOE finalised the remediation strategy to be undertaken at Moab which included active groundwater remediation and off­site disposal of the tailings pile and other contaminated materials at the Crescent Junction disposal site.26 The Rifle site consists of two old uranium processing plants: Rifle Old Processing Site and Rifle New Processing Site. Tailings and tailings-contaminated material from Rifle were transferred to the Rifle disposal site approximately six miles north of the Rifle New Processing Site and surface remediation was completed in October 1996. Contaminants of concern in the groundwater at both sites include arsenic, molybdenum, selenium, nitrate, uranium and vanadium, with contamination at New Rifle extending approximately three miles west of the site. Groundwater remediation is being achieved through natural flushing of the groundwater in conjunction with contaminant monitoring.27 The in situ remediation of uranium was examined in a field scale study in 2003 in which acetate was injected into the subsurface over a three month period in order to stimulate microbial reduction of soluble U(vi) to insoluble U(iv) (ref. 28) and is discussed in detail later in this chapter. The Savannah River Nuclear Facility, South Carolina, was used to refine nuclear material for use in the United States defence program. The site used a system of canals and reservoirs to disperse heat from the reactors and consequently, various ponds connected to this system received cooling water discharges from the reactors. One such pond, Pond B, received discharges containing fission products such as Cs, Sr and Pu. Radionuclide input peaked in 1963 and 1964, believed to be caused by the leakage of fuel elements stored in a water-filled basin in the reactor.29 The vast majority of both 137Cs (98%) and 90Sr (85%) were found to be in the pond sediments.29

A number of other sites located in the United States have a more complicated environmental legacy left by the nuclear industry and are discussed below in more detail.