The generation of nuclear energy begins with uranium mining and milling. These activities are at the ‘‘front end’’ of the nuclear fuel cycle (Fig. 1). The cycle continues through conversion and enrichment and fuel fabrication for light water reactors (natural uranium is fuel for heavy water reactors),with each of these operations having associated costs (see Section 3.3.1). The ‘‘back end’’ of the cycle includes spent nuclear fuel (SNF) management, reprocessing, and high-level radioactive waste disposal. There are two types of back ends: once – through and closed cycle. Under the once-through fuel cycle, SNF is cooled at the NPP, stored or transported to a centralized facility, and finally shipped to a geologic repository, such as the one being planned in the United States at Yucca
Mountain, Nevada. The closed-cycle back end involves reprocessing SNF to recycle uranium and plutonium for fuel. SNF can only be recycled in current NPPs a few times before the buildup of unstable plutonium isotopes renders the fuel unusable. Eventually, recycled SNF is separated into waste streams, some of which are processed for geologic disposition.