The McArthur River Project High Grade Uranium Mining

Abstract

The McArthur River deposit, discovered in 1988, is recognized as the world's largest, highest grade uranium deposit, with reserves and resources of 416 million lb U308 at an average grade of 15% U3O8. Underground diamond drilling along 300 metres of the 1.7Km strike length has proven more than six times the uranium expected from surface drilling interpretation. Hence, there is excellent potential for additional reserves. The deposit is in northern Saskatchewan, on the eastern edge of the Athabasca Basin, northeast of the Key Lake mine. The ore is approximately 550 metres underground, associated with a major thrust fault, which has caused fracturing of the footwall Athabasca sandstone and gives the potential for significant water flows near the ore body. Mining this high-grade ore body presents serious challenges in controlling radiation and in dealing with high water pressures. Experience from the underground exploration programme has provided the information needed to plan the safe mining of the massive Pelite ore zone, which represents the most significant source of ore discovered during the underground drilling programme, with 154 million pounds of U3O8 at an average grade in excess of 19%.Non-entry mining will be used in the high-grade ore zones. Raise boring will be the primary method to safely extract the ore, with all underground development in waste rock to provide radiation shielding. Water will be controlled by grouting and perimeter freezing. The ore cuttings from the raise boring will be crushed and ground underground and pumped to surface as a slurry, at an average daily production of 125 tonnes. The slurry will be transported to the Key Lake mill and diluted to 4% before processing. The annual production is projected to be 18 million lb U3O8.The environmental assessment panel recommended in February, 1997, that the project be approved. Both provincial and federal government approvals were received in May, 1997.The licensing of various details of the construction by the Atomic Energy Control Board and by the Province of Saskatchewan is proceeding. The presentation will focus on the activities undertaken since discovery, including the methods to be utilized to safely mine this high-grade ore body. Radiation protection,environmental protection and worker health and safety will be discussed in terms of both design and practical implementation.The project is estimated to cost C 450,000,000 and require two years of development. Production is anticipated to start in the fall of 1999.