The Potential for Economic Recovery of Metals from the Sillamäe Site

Abstract

The Sillamäe tailings pond contains some 12 million tons of waste material from various industrial activities over the past 50 years. These activities included the production of electricity from local oil shales, the extraction of uranium from local and imported uranium ores, and the extraction of rare earth metals and chlorides from imported loparite ores.’ The process wastes were initially deposited on an unprepared surface, and later behind a wall constructed of this early deposited material, creating a sandy/muddy mass partially covered by a solution whose pH varies between 6 and 10. This formation is typically called a tailings dam or tailings pond. From the data in Ehdwall et al. [3], it appears that the Sillamäe tailings pond, which has a solids volume of 8 million m³ and covers an area of 330,000 m², consists of a lower layer of oil shale ash, a middle layer of uranium tails, and an upper layer of loparite tails mixed with oil shale ash, corresponding to the chronological sequence of industrial activity at Sillamäe. The tailings dam wall consists mainly of uranium tails, but includes some oil shale ash. According to [3], the total solids content of the tailings pond weighs some 12 million tons, although Silmet reports that the pond contains only 4 million tons of uranium tails, 1.5 million tons of oil shale ash, and 140,000 tons of loparite tails. Thus, there is some discrepancy as to the quantity of material within the pond.