Uranium is the key to the exploitation of nuclear energy. As such, it has developed an exotic reputation, but it is in fact a very common element as common as tin. It is present in rock and soil, and in water in trace amounts and, in much the same way as other minerals like tin, is found in various concentrations in different types of deposit. Rocks such as uraninite, autunite, uranophane, pitchblende or coffinite can be as much as 2 per cent uranium, but it also exists at a few parts per million in granite and many other rocks and at much greater concentration in deposits mined for uranium fuel. Uranium oxide was used to give colour to ceramic glazes as far back as the first century AD, but it was not until the 18th century that it was isolated and named. It was separated from pitchblende (the so-called black mineral) in 1789, by a German chemist named Martin Klaproth, and named after the recently discovered planet Uranus, which in turn had been named after Urania, the muse of astronomy and geometry. Uranium metal was first produced from uranium oxide by Eugene-Melchior Peligot in 1841. It is a silver-white metal, denser than lead. The metal that had been so little known for so many centuries was the centre, over the next few decades, of a frenzy of scientific research and discovery that revealed that the atom had a complex internal structure and, moreover, one that was not unchangeable. Along the way, it also confirmed Albert Einstein's theories on mass and energy and laid the foundations for the exploitation of the power of the nucleus.

Nuclear reactor safety requires that three functions should be fulfilled at all times: 1) The chain reaction must be controlled and so must the power generated. 2) The fuel must be cooled during and after operation, including after the chain reaction has stopped, as residual heat remains in the reactor core caused by continued radioactive disintegrations and fissions. 3) Radioactive products must be retained and controlled. The safety philosophy relies upon two main principles: three protective barriers and so-called defence in depth. The three protective barriers are intended to contain radioactivity in all circum stances. The first barrier is the fuel, inside which most of the radioactive products are already trapped. The fuel is contained within a metal cladding (magnox, steel or zircaloy) which presents a barrier to stop the products escaping. The second barrier is the reactor coolant system, housed within a containment enclosure which includes the reactor vessel containing the core constituted by the fuel within its cladding. For the third barrier the reactor coolant system is also enclosed in a containment including a biological shield made of very thick concrete. For the European PWR now under construction in Finland, for example, this construction is a double shell resting upon a thick basemat, whose inner wall is covered with a leak-tight metal liner.

This chapter presents a discussion on the use of uranium fission reactor fuel. The discussion proceeds from uranium mining to its conversion and enrichment and eventually to fuel fabrication, cladding, and fuel pin construction. Uranium sources are also included as well as management of spent nuclear fuel and fuel life cycle analysis.

The UK currently has a stake in two reactor designs but is in the process of disposing of its interest. One is the Pebble-Bed reactor, whose design and development are now being spearheaded by Eskom in South Africa, which already has one nuclear power plant at Keoberg. The Pebble-Bed reactor is very closely based on high-temperature gas reactor designs, with small spherical fuel elements made of graphite and uranium. The Pebble Bed is at the detailed design phase and as such is unlikely to be on the drawing board for a new reactor in the UK. The UK's second stake in anew reactor is via BNFL's Westinghouse subsidiary, in the form of the AP600 and its larger variant the AP1000.

In the Generation IV programme the potential uses of these reactors may be broader than the production of electricity. They may also be sited on an industrial site (and sized very differently from current reactors) so that the 60 per cent or more of heat production that is currently vented into air or otherwise wasted can be used to provide process heat for industry. In some designs the reactor is directly linked to a hydrogen production process, anticipating a shift towards using hydrogen, instead of oil, as an energy transfer medium for vehicles and other uses. Finally, the new reactor designs are intended to 'burn' a broader range of fissile substances so that the problem of disposing of plutonium and other long-lived wastes is reduced as they can be transmuted in the reactor. There are six reactors in the programme at present; the U S is expected to focus on three for further development. The following summarises the reactor system descriptions in the Technology Roadmap for Generation IV Nuclear Energy Systems and its assessment of research and development needs and other issues associated with each design.