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The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end , which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end , which are necessary to safely ...
Natural uranium (NU or U nat [1]) is uranium with the same isotopic ratio as found in nature. It contains 0.711% uranium-235 , 99.284% uranium-238 , and a trace of uranium-234 by weight (0.0055%). Approximately 2.2% of its radioactivity comes from uranium-235, 48.6% from uranium-238, and 49.2% from uranium-234.
While the thorium cycle may be proliferation-resistant with regard to uranium-233 extraction from fuel (because of the presence of uranium-232), it poses a proliferation risk from an alternate route of uranium-233 extraction, which involves chemically extracting protactinium-233 and allowing it to decay to pure uranium-233 outside of the reactor.
Uranium alloys that have been used include uranium aluminum, uranium zirconium, uranium silicon, uranium molybdenum, uranium zirconium hydride (UZrH), and uranium zirconium carbonitride. [3] Any of the aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle.
Because of this, a light-water reactor will require that the 235 U isotope be concentrated in its uranium fuel, as enriched uranium, generally between 3% and 5% 235 U by weight (the by-product from this process enrichment process is known as depleted uranium, and so consisting mainly of 238 U, chemically pure).
Change of content of Uranium-235 in natural uranium; the content was 3.65% 2 billion years ago. A key factor that made the reaction possible was that, at the time the reactor went critical 1.7 billion years ago, the fissile isotope 235 U made up about 3.1% of the natural uranium, which is comparable to the amount used in some of today's reactors.
The advanced reprocessing of spent nuclear fuel is a potential key to achieve a sustainable nuclear fuel cycle and to tackle the heavy burden of nuclear waste management. In particular, the development of such advanced reprocessing systems may save natural resources, reduce waste inventory and enhance the public acceptance of nuclear energy.
Uranium-233 is a fissile isotope that is bred from thorium-232 as part of the thorium fuel cycle. 233 U was investigated for use in nuclear weapons and as a reactor fuel. It was occasionally tested but never deployed in nuclear weapons and has not been used commercially as a nuclear fuel. [27]