Nuclear Fuel Cycle
The nuclear fuel cycle comprises a set of industrial processes for producing electricity from uranium. These processes are carried out in nuclear fuel-cycle facilities, as illustrated in Figure S.1. Facilities comprising the front end of the nuclear fuel cycle are involved in the extraction of uranium from the environment and its fabrication into fuel for nuclear reactors. The uranium fuel is utilized in nuclear power reactors to produce electricity. Modern reactors typically generate on the order of 3000 megawatts of thermal power and produce about 1000 megawatts of electrical power. Facilities comprising the back end of the nuclear fuel cycle are involved in managing this fuel after it has been utilized in reactors; fuel management activities can involve recycling, storage, and/or disposal. The only civilian back-end facilities currently in operation in the United States are interim storage facilities for managing used fuel, most of which are located at commercial nuclear power plants. In the United States, almost all of these fuel storage facilities are co-located with nuclear plants.
The USNRC regulates five types of front-end fuel-cycle facilities:
Mining facilities: Facilities that are used to extract uranium from the environment. Currently, uranium is extracted using either conventional mining or leaching methods. The former method involves the physical removal of uranium-bearing ores from the subsurface in underground and open-pit mines. The latter method includes in situ leaching, in which solutions are pumped into the subsurface to extract uranium, and heap leaching, in which solutions are sprayed onto piles of mined rock to extract uranium. This study is concerned only with in situ leaching facilities. (The USNRC did not ask the NAS to examine conventional mining facilities because these facilities are not regulated by that agency.)
Milling facilities: Facilities that are used to process uranium ore or leach solutions to produce uranium oxide (U3O8) powder, or yellowcake. Mills can be standalone facilities, or they can be integrated into a uranium extraction operation. The former type of facility is used for conventional mining operations, where a single mill can service several mines, whereas the latter type of facility is used for in situ leaching operations.
Conversion facilities: Facilities that are used to convert yellowcake into a solid hexafluoride form (uranium hexafluoride, UF6). This compound sublimes to form a gas at about 56°C at standard atmospheric pressures. The gaseous form of this material is used in subsequent processing steps.
Enrichment facilities: Facilities that are used to increase the concentration of
of countywide data made it difficult to discern local effects around nuclear facilities, especially in geographically extensive counties. The investigation also focused primarily on cancer mortality, because good-quality cancer incidence data were largely unavailable at the time the study was conducted. (Incidence may be a better indicator of risk than mortality because advances in cancer treatments have lowered mortality rates for many types of cancer, including leukemia.)