Contamination and resultant health-hazard problems exist at uranium milling sites throughout the U.S. Concern about this contamination was sufficient to result in the passage of the Uranium Mill Tailings Remediation and Control Act of 1978, which required cleanup at all current and former U.S. milling sites. 134
This mill tailings law contains two sections. The first regulates the operation and cleanup of mill sites that are currently under NRC or state licenses, the cost of which is to be paid for by the company which produced the tailings. The second section put the DOE in charge of cleaning up abandoned sites, the cost of which is to be split between the federal government and the affected state government, at a rate of 90 percent/10 percent. These sites are subject to cleanup under DOE's Uranium Mill Tailings Remedial Action Program (UMTRAP).
Under provisions of the law, the EPA was to set general environmental standards for long-term tailings control, and the NRC was to establish licensing requirements for active milling operations.135
In 1983, on two separate dates, the EPA issued its standards for cleanup of mill tailings at active and abandoned sites.136 These standards establish criteria for tailings isolation in lined impoundments which limit radon emission, include groundwater protection requirements, and limit radium concentration in contaminated soils. These standards extend for a time frame of 200 to 1,000 years after the closure of the site.
As of 1985, estimates indicated that the cost of the cleanup at the 28 currently licensed U.S. mills under EPA's minimum national standards would range from $1 billion to $4 billion.137 Over the last several years, little progress has been made, and at least 13 out of the 25 licensed uranium milling sites which have operated remain unstabilized or only partially stabilized.138
As is apparent from the 1,000 year time frame in the regulations, none of the remedial programs contain provisions for protecting future generations for time frames compatible with or longer than the radium-226 half-life (1,600 years) and most certainly not the thorium-230 half-life of 80,000 years. Putting tailings in lined impoundments may prevent leakage in the near term, and perhaps even for the 1,000-ear period which the regulations cover. However, it provides little assurance for the great majority of the hazardous life of the principal radionuclides of concern, radium-226 and thorium-230.
We note that the main radioactive hazards from mill tailings, thorium-230 and radium-226, can, in principle, be separated from the tailings and treated as repository-bound long-lived wastes. We here make a preliminary estimate of what this would entail.
The actual costs of separation would vary from site to site and depend on the concentration of these elements in the tailings. Such separation need not be as expensive as might first seem, since there is no need for the "product" (i.e. the separated thorium and radium) to be pure, as is the case for the initial uranium separation or as was the case for the radium industry in the early part of this century. The principal requirement is that substantially all of the radium and thorium be removed from the tailings, and be in a much smaller volume so that they can be disposed of along with other highly radioactive long-lived wastes.
There are on the order of 200,000 curies each of radium-226 and thorium-230 in the roughly 250 million metric tons of uranium mill tailings in this country.139 The respective weights of these elements are about 200 kilograms and 10,000 kilograms.140 If the mill tailings are processed so that the radium and thorium content in the "product" is about one part in a hundred by weight, the total weight to be disposed of as long-lived, repository-bound waste would be about 1,000 metric tons. This is less than one percent of the weight of encapsulated reactor spent fuel, and would therefore be expected to affect only negligibly the size of a repository.
We should note, however, that there are potential drawbacks to this approach, and the idea needs to be considered carefully. For example, the resulting repository-bound radium and thorium concentrates would of course be quite radioactive, with concentrations of about 640 curies per cubic meter, based on the above assumptions.141 Thus, issues of the risks from waste handling and potential worker exposures would need to be carefully weighed.
Since the total weight of radium and thorium waste in a mixture containing just one part in a hundred of radium-226 and thorium-230 is not huge, it indicates that extraction of these radionuclides is technologically feasible for repository disposal, and therefore should be considered.
Return to Publications Main Page
Return to IEER Home Page
Institute for Energy and Environmental Research
Comments to Outreach Coordinator, ieer@ieer.org
Takoma Park, Maryland, USA
Last Updated October, 1996
134. Public Law 95-604, cited in NAS 1986, p. 17.
135. The genesis of these regulations is discussed in SRIC 1985, pp. 110-113.
136. The standards for inactive sites (40 CFR 192, Subpart A) were published in EPA 1983c; active site standards (40 CFR 192, Subpart D) were published in EPA 1983a.>
137. SRIC 1985, p. 108.
138. DOE 1990d, pp. 130-131. The status of these mills is apparently unchanged since the issuance of a similar report in 1988 (DOE 1988c).
139. Assuming that radium-226 and thorium-230 each exist in the tailings at concentrations of about 800 picocuries per gram. Based on EPA 1983b, Table 3-1, p. 3-6, this is probably an overestimate and therefore conservative. The source lists radium concentrations at licensed mill tailing piles in the U.S. which range from about 200 to 850 picocuries per gram, with many in the range of 400 to 500 picocuries per gram.
140. Based on specific activities of 1 curie per gram for radium, and 0.02 curies per gram for thorium-230.
141. Based on an assumed density similar to that of the mill tailings themselves, i.e. 1.6 metric tons per cubic meter (DOE 1990d, p. 131).