Decommissioning of Elliot Lake Tailings

(last updated 15 Sep 1996)


> View Rio Algom Quirke Tailings (water covered): Schematic profile · Aerial view Aug. 1999 (BHP Billiton)

Uranium Tailings in Elliot Lake


(reprinted here with permission from Nuclear Awareness Project)

The majority of uranium tailings in Canada -- about 200 million tonnes -- are located in Elliot Lake. However, neither the federal or provincial governments can confirm exact locations and quantities. There are about 60 million tonnes of tailings at Rio Algom's Quirke and Panel mines, and about 70 million tonnes at Denison's Stanrock and Denison mines. In addition, Rio's Stanleigh mine is still operating in Elliot Lake until 1996 and has produced over 15 million tonnes of tailings. Former Rio Algom mines in the Elliot Lake area include Nordic, Lacnor, Spanish American and Pronto. There are also a number of areas where tailings have spilled accidentally over the years. The Agnew Lake site near Espanola, while not in the Elliot Lake basin, also has an impact on the regional environment.

Waste from uranium mining takes the form of both waste rock and tailings. In the mill, uranium ore is crushed and chemically treated to remove uranium. The grade of ore in Elliot Lake is typically 0.1% U3O8 (uranium concentrate, known as yellowcake). Thus every tonne of ore mined in Elliot Lake yielded a tonne of tailings, as well as about two tonnes of process liquid. The leach residue still contains most of the radioactive decay products of uranium. The solids are known as tailings. About two thirds of the tailings are similar to course sand, although the finer remainder (known as slimes) contain a higher concentration of radionuclides. The tailings are normally transferred in a slurry and historically were simply dumped into nearby depressions or lakes, depending on nature to do its best to cope with the environmental devastation.

The uranium ore of Elliot Lake contains the sulphide mineral pyrite, which can oxidize into sulphuric acid. Acidic drainage is a major environmental problem with uranium tailings in Elliot Lake. Acidity also mobilizes some metals such as radium, copper, zinc, nickel and lead.

In addition to the problem of acidic drainage, uranium wastes have the problem of radiological contamination. Thorium-230 is the uranium decay product with the longest lifetime -- it has a "half life" of 76,000 years, thorium-230 turns into radium-226, one of the radionuclides of most concern in uranium tailings. Radium is chemically similar to calcium, and thus if ingested, concentrates in the bones, teeth and breast milk of mammals (including humans), where it increases the risk of cancer. Radium in turn produces radon gas (radon-222), which is known to cause lung cancer when inhaled. Because thorium-230 is so long-lived, radium and radon are being constantly produced and released from tailings over an extremely long period of time. The amount of any radioactive element decreases by a factor 1,000 in ten half lives. Thus, in 760,000 years, one gram of thorium-230 will be reduced to a milligram. For human purposes, radiological contamination from uranium tailings is a problem forever.

It was only following public attention in the 1960s that regulatory attention began to be paid to uranium tailings in the 1970s, looking at long-term radiological and acidification impacts. The theoretical objective is to reduce the flow of water through the tailings, and to eliminate the flow of contaminants from the tailings piles. In the 1970s, rudimentary treatment processes were implemented that can be best described as a form of modified dumping. This remains the current practice. After the settling of solid materials, waste water flows into holding ponds, where barium chloride is added to precipitate out radium-226, which is left in a sludge on the bottom of the holding ponds. The tailings are also neutralized to reduce acid in surrounding waters. Although there are gates on some roads to tailings sites in Elliot Lake, sites are readily accessible, being neither fenced nor guarded.

There are a number of possible remedial actions for uranium tailings, including waste rock or earth cover; water cover; pyrite removal; removal of harmful radioactive substances; and the use of various types of impervious covers or liners. Tailings treatment for new mines is entirely different from historic sites, where tailings were generally dumped in the nearest lake or ground depression. Various options may involve the moving of existing tailings sites. In the current environmental assessment, both Denison and Rio Algom want to cover most of their tailings with a few feet of water, as a means of preventing acid formation and reducing radiological emissions. The water cover option also happens to be the cheapest option. However, in the long run, the method is dependent on engineered structures such as dams to maintain water levels. It is highly unlikely that these structures will be able to survive for the thousands of years during which the tailings will remain dangerous.

Spill Charge Against Rio Algom -- In August 1993, two million litres of contaminated water spilled from a tailings site at Rio Algom's Stanleigh mine in Elliot Lake. The spill took place as a result of a power failure. Rio Algom has been charged by the Atomic Energy Control Board with one count of failure to provide appropriate training for its employees, and one count of failure to prevent the spill under "reasonably foreseeable circumstances". The radiologically and chemically contaminated water spilled into McCabe Lake.

Nuclear Awareness News is the newsletter of Nuclear Awareness Project, a non-profit environmental group based in Uxbridge, Ontario, Canada. We can be reached at Box 104, Uxbridge, Ontario, L9P 1M6, Canada, Tel/fax = +1-905-852-0571, e-mail = The editor of Nuclear Awareness News is Dave Martin. These articles may be reprinted with acknowledgement.

Hearings on Elliot Lake Decommissioning Proposals:

Northwatch attacks water cover concept for Elliot Lake uranium tailings decommissioning (Ontario, Canada)

Public hearings were held end of January 1996 on the decommissioning proposals for four giant uranium mill tailings sites located in the Elliot Lake area, Ontario, Canada: there are about 60 million tonnes of tailings at Rio Algom's Quirke and Panel mines, and about 70 million tonnes at Denison's Stanrock and Denison mines. The hearings were held with participation from provincial and national environmental groups and the local native group - the Serpent River Band. The non-binding recommendations of the Review Panel were released on 21 June 1996 (see above).

The main comments and recommendations presented by the provincial environmental group Northwatch are the following; they were prepared on behalf of Northwatch by Wm. Paul Robinson of Southwest Research and Information Center (Albuquerque, New Mexico, USA):

View full text of comments and recommendations (67k).

From a world uranium policy standpoint the Panel proceeding was the first large scale review of a soft, non-durable cover for a permanent uranium tailings repository; and the decisions here will have a powerful effect on other Canadian sites or site where Canadian consultants on climatic and geologic analogs come into play.

Northwatch, P.O. Box 282, North Bay, Ont. P1B 8H2, Canada
Tel. +1-705-497-0373, Fax: +1-705-476-7060, Email:

Environmental Impacts of Elliot Lake Mill Tailings

by R Leigh, M Resnikoff and A Vanrenterghem
Radioactive Waste Management Associates

March 30, 1992 (Updated November 14, 1995)

Radioactive Waste Management Associates
526 W. 26th Street Rm.517, New York, NY 10001, USA
Tel. +1-212-620-0526, Fax: +1-212-620-0518, E-Mail:


For each year's operation of a CANDU reactor, uranium must be mined and milled and the waste, the mill tailings, laid out on the earth's surface. An inert radioactive gas, radon, is released to the air from the tailings pile, and radioactive thorium, radium, polonium and lead are released to the water or suspended by wind into the air. The health effects resulting from these releases, both in contemporary populations and in succeeding generations is clearly the most important detrimental effect resulting directly from the mining of uranium.

In a series of detailed technical reports for the Atomic Energy Control Board , IEC Beak Consultants Ltd (Beak83) calculated the radiation doses to the local and global population due to one hypothetical Elliot Lake tailings site. In this report for Northwatch, we have used these results to project the dose due to all tailings at Elliot Lake. We then used two estimates of the expected fatal cancers resulting from unit doses to project low and high estimates of the resulting health effects. Following Beak, we have projected doses and consequent health effects both for the local population and for the globe as a whole. Also following Beak, we have broken these out according to the contributions of aquatic releases, radon gas and wind suspension of particulates. The results of these calculations are presented in Tables 1 through 3 and discussed in the Summary section immediately below.

We then provide a comparison of Beak's base case and ours and a derivation and assessment of our scaling factors. This is followed by a description of Beak's modelling of Aquatic Releases and then the derivation of our projections of doses and health impacts resulting from aquatic releases. The next four sections provide a similar analysis of Beak's modelling of atmospheric releases of radon and of particulates and our projections from them. We then offer our assessment of where their model may have omitted plausible chains of events leading to significant releases of radioactive material, indicating that the results we present, although uncertain, represent a low estimate of potential health impacts. Because of high concentrations of iron in Elliot Lake tailings and snow cover during part of the year, the average radon exhalation rate shown here are less than averages presented in UNSCEAR.

In a series of report since 1983, NUTP has improved the Beak model. Modelling of the uranium tailings pile has been refined, additional radionuclides and dose pathways incorporated, and in-growth of daughter products in downstream water bodies accounted for. The effect of these refinements has been to increase the projected doses. However, major episodic events, such as floods, dam breaks, and major erosion, continue to be ignored by the NUTP studies. For long time periods, the probability of such events approaches unity and could cause major environmental impacts. We discuss these events in qualitative terms. Since these subsequent NUTP studies pertain primarily to critical receptors and not to regional and global population groups, we did not quantitatively incorporate the results here.

Finally we discuss the impact of various alternative methods of containing the mill tailings, including both Beak's proposals and our own suggestions for long term containment with the smallest possible health effects. A section is devoted to the economic costs of remediation measures.

View Summary (15k)

View complete text (115k)

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