Light Water Reactors with Thorium–Uranium Heterogeneous Fuel in a Nuclear Energy System.

The fuel of modern light water reactors contains a large amount of 238U. On one hand, it makes it possible to breed a certain amount of fuel even in a thermal reactor. On the other hand, it absorbs neutrons and is a source of minor actinide generation. This work is focused on the concept of heterogeneous fuel. According to this concept, fissile and fertile materials are put into different fuel pellets which are arranged inside the same fuel pin of a conventional water-moderated water-cooled reactor. In this approach, a large amount of fuel nuclides will be concentrated in the fuel pellets of high enrichment. When using the fuel pellets containing microfuel in the graphite matrix, it will be possible to achieve high burnups, which will allow them to be unloaded from the core and sent for direct disposal without reprocessing and fission product extraction. At the same time, the amount of fission products will be reduced in the pellets with fertile materials, which will facilitate the process of their reprocessing. On one hand, this approach will allow producing a certain amount of fissile material and using a simplified reprocessing technology for its extraction. On the other hand, in terms of this concept, it is possible to significantly reduce the risks of radiation impact to the environment owing to nearly complete burning of fissile material in the fuel pellets and the refusal to reprocess them. This work presents the nuclide balances for the fuel pin lifetime in the uranium-plutonium and thorium-uranium fuel cycles of a light water reactor with heterogeneous fuel. [ABSTRACT FROM AUTHOR]

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