The nuclear fuel cycle is a multistage industrial process revolving around the utilization of uranium to produce electricity. The front-end of the fuel cycle begins with mining uranium out of the ground, milling it into a more concentrated form (e.g., U3O8), converting it either into a useable form for enrichment for light water reactors (LWR, i.e., UF6) or into a reactor-grade form for CANDUs (i.e., UO2), enrichment of uranium to increase fissile content in LWR fuel, fabrication of the fuel into assemblies, and the service period in-reactor. The back end of the fuel cycle may take two different paths: (1) an open fuel cycle, whereby irradiated fuel discharged from the reactor is put into temporary wet storage and then dry-storage with the ultimate hope of permanent disposal or (2) a closed fuel cycle, whereby irradiated fuel discharged from the reactor undergoes a reprocessing stage to extract useable components from the used fuel (i.e., uranium and/or plutonium), recycling usable components from the reprocessing stage to fabricate new fuel (e.g., MOX), whereby nonrecyclable components are disposed of as waste. This chapter describes the mining and milling stages of the uranium fuel cycle with a focus on fuel chemistry.
