Abstract

Although uranium was known in Wyoming in the 1910s, very little attention was given to the element until the procurement programs of the U.S. Atomic Energy Commission (AEC) commenced in the early 1950s. In October, 1951, uranium was discovered in the Wasatch Formation of the Powder River Basin, and in May, 1952 deposits were located in Lower Cretaceous rocks of the Black Hills in Crook County. The Powder River Basin discovery soon led to similar discoveries in Tertiary rocks in the Wind River, Great Divide, Washakie, and Shirley basins. Initial ore production was shipped to mills and/ or ore buying stations out of state.

Beginning in early 1955, the AEC established an ore buying station at Riverton, Wyoming. This was followed by another station at Crooks Gap in late 1956. By 1956, companies had developed substantial reserves and contracts were signed with the AEC to produce uranium concentrates at mills to be built at Crooks Gap and in the Gas Hills. Additional mills were later built at Riverton, in the Gas Hills, and in the Shirley Basin. By 1962, six mills were producing uranium concentrates for sale to the AEC. During that year, a record 6,110,000 pounds U₃0₈ were sold to the AEC. Production declined after 1962 due to AEC procurement limitations. When the AEC's procurement program ended on December 31, 1970, the agency had purchased 51,046,013 pounds U₃0₈ from Wyoming mills at a cost of $405,976,300.

A second boom occurred in the late 1970s and early 1980s as the need for uranium for nuclear power plants increased. Four new mills were constructed, one each in the Shirley and Great Divide basins, and two in the Powder River Basin. Solution mining technology was found to be applicable to deposits in Tertiary sandstones in the basins. The boom was short lived, due to overproduction and the lack of acceptance of nuclear power by the general public, especially following the Three Mile Island reactor incident in 1980. Since 1980, when an all-time record of 12,072,000 pounds U₃0₈, in concentrate, were produced, uranium production has been declining. Currently (March, 1991), there are only one openpit mine mill complex and one commercial solution mining project operating in Wyoming. Since 1957, mills and solution mining operations in Wyoming have produced nearly 188 million pounds U₃0₈, which accounts for 22 percent of the total domestic production. Developed ore reserves remain at many properties and the potential to discover additional deposits is good. Higher uranium prices and a strong market are needed for uranium production to increase in Wyoming.