Today, 31 countries operate ∼ 450 nuclear power reactors supplying electric power to ∼ 1 billion people, ∼ 15% of the world population. Nuclear reactors generate ∼ 17% of global electric power needs and a number of industrialized countries depend on nuclear power for at least half of their electricity. In addition, ∼ 30 nuclear power reactors are presently under construction worldwide (Macfarlane and Miller, 2007). A comprehensive summary of the principles, practices and prospects for nuclear energy may be found in Bodansky (1996). Concerns regarding energy resource availability, climate change, air quality and energy security imply a continuing demand for nuclear power in the world energy budget (Craig et al., 2001). However, to date no country has solved the problem of long-term disposal or storage of nuclear waste. Without a long-term solution, the viability of nuclear energy as an increasingly significant contributor to power generation in the long-range future remains unclear. There is broad consensus that geologic disposal is the safest feasible long-term solution to high-level waste and spent-fuel disposal. Although a number of countries have ongoing geologic repository research programs, there is presently no operational geologic repository for spent fuel or high-level waste on Earth. In the United States, where spent nuclear fuel and high-level waste amounts to ∼ 50 000 metric tons, ∼ 15% of the world total, implementation has proven to be challenging both technically and politically. Nuclear waste is currently stored on-site at existing nuclear power stations and at several temporary storage facilities.