Uranium–uranium dating
U, with a half-life of about 4.5 billion years, decays to U through emission of an alpha particle to thorium-234 (Th), which is comparatively unstable with a half-life of just 24 days. Th then decays through beta particle emission to protactinium-234 (Pa)). This decays with a half-life of 6.7 hours, again through emission of a beta particle, to U. This isotope has a half-life of about 245,000 years. The next decay product, thorium-230 (Th), has a half-life of about 75,000 years and is used in the uranium-thorium technique. Although analytically simpler, in practice U/U requires knowledge of the ratio at the time the material under study was formed and is generally used only for samples older than the ca. 450,000 year upper limit of the Th/U technique. For those materials (principally marine carbonates) for which these conditions apply, it remains a superior technique.
Peak uranium
Various agencies have tried to estimate how long these resources will last.The European Commission said in 2001 that at the current level of uranium consumption, known uranium resources would last 42 years. When added to military and secondary sources, the resources could be stretched to 72 years. Yet this rate of usage assumes that nuclear power continues to provide only a fraction of the world’s energy supply. If electric capacity were increased six-fold, then the 72-year supply would last just 12 years.The world's present measured resources of uranium, economically recoverable at a price of US$130/kg according to the industry groups OECD, NEA and IAEA, are enough to last for 100 years at current consumption.According to the Australian Uranium Association, yet another industry group, assuming the world's current rate of consumption at 66,500 tonnes of uranium per year and the world's present measured resources of uranium (4.7 Mt) are enough to last for 70 years.