The commercial development of uranium production facilities in the United States is influenced principally by demand for uranium, and not the available supply, as given by the estimated ore reserves. Uranium is unique in that it is used primarily for one purpose: nuclear fuel. If National Defense requirements are ignored, the principal demand for uranium stems from its use in nuclear power plants to generate electricity. The uranium market has never been what economists term "pure competition," that is, a marketplace with many buyers and sellers, each of whom operates independently. Three principal types of expenditures are of concern to most uranium producers: exploration costs; mining costs; and milling costs. While it is difficult to obtain specific cost estimates for a particular uranium property, there are some general cost estimates available. These cost estimates apply to two types of expenditures: capital investment and operating expenses.