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Nuclear Fuel |
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Nuclear fuel is loaded into new nuclear reactors in the form of fuel assemblies, long, thin zirconium tubes containing pellets of uranium. These will stay in the reactor for about 3 years until the reactivity declines to the extent that replacement is warranted. LWRs, comprising 90% of today’s reactors, were traditionally shut down once per year (an “outage”) when one third of the fuel would be replaced, but many reactors today have longer operating cycles, with outages only every 18 or 24 months. After discharge from the reactor, used nuclear fuel is cooled for several years in large ponds of water. Thereafter there are essentially two options – either reprocessing the used fuel, to separate uranium and plutonium which may be re-introduced into the nuclear fuel cycle, or storing the used fuel for longer before sending it to a deep geological repository.
The “front end” of the nuclear fuel cycle comprises the stages up to fuel fabrication, where the fuel assemblies are prepared. The “back end” is the route followed by the used fuel, which can include reprocessed uranium and plutonium re-entering the front end. Uranium production is the starting point of the front end and it goes through stage of conversion and enrichment (at least for LWRs – PHWRs run on natural uranium) before fuel fabrication.
Uranium is not scarce in any geological sense and over 2 million tonnes have been mined since the dawn of the nuclear age in the 1940s. Identified resources exist in many politically stable countries, more than adequate to fuel any conceivable expansion of nuclear power this century. The world uranium market has been characterized by periods of extreme boom and bust, caused initially by the demands of military programs and latterly by the on-off civil nuclear plans. The period from the 1980s to 2003 saw a long depression in uranium, with prices at levels insufficient to allow any but the most efficient producers to survive. In many years, 40% of reactor requirements were fulfilled by secondary supplies rather than primary production, sourced from either commercial inventories built up in previous boom periods or former military uranium reaching the civil market. Since 2003, however, uranium prices have risen sharply, encouraging an upsurge in exploration by up to 400 junior uranium companies, adding to the established market participants such as Cameco, Rio Tinto, Areva, BHP Billiton and Kazatomprom. Few of these will ever enter the production phase, but some such as Paladin and Uranium One are already doing so and will participate in a likely production boom over the next few years.
Conversion is an intermediate step in the nuclear fuel cycle, where uranium is converted from oxide to fluoride form for the enrichment stage (which requires uranium to be in a gaseous form). It is carried out in a few specialist plants throughout the world. LWRs require the U-235 isotope of uranium to be increased from the natural 0.7% to 3-5%. This is a major, technically complex, step in the cycle and has historically accounted for slightly more of the fuel cost than uranium supply itself. Large gaseous diffusion enrichment plants owned by USEC in the United States and by Areva in France are now gradually been replaced by new centrifuge enrichment facilities, a technology mastered by Urenco in Europe and by the Russians. This is much less energy intensive than gas diffusion and capacity can be added on a modular basis. Upwards of $10 billion will be invested in new centrifuge facilities over the next 5-10 years.
Fuel fabrication is a specialized service to reactor operators, rather than a homogeneous commodity like uranium, conversion and enrichment. As such, it takes place at a greater number of suppliers worldwide, in many cases national suppliers close to the reactor location.
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