Burn up and neutronic evaluation of thorium-uranium fuel in heavy water research reactors using MCNPX code

One of the main characteristics of heavy water research reactors is their high production of plutonium. This work demonstrates the possibility of reduction of plutonium production and other actinides in heavy water research reactors. Among the many ways for reducing plutonium production in a heavy water reactor, in this research, changing the fuel from natural uranium to thorium-uranium mixed fuel was focused. For this purpose, different compositions of thorium-uranium fuel were used in our calculations. Natural uranium oxide was regarded as the reference fuel. Neutronic parameters for each fuel were calculated by MCNPX2.6 code linked to a fuel depletion code (CINDER90). The obtained results indicated that thorium-uranium fuels have some advantages compared to natural uranium fuel. Thorium-Uranium fuels could dramatically reduce plutonium production up to 90% in a year, compare to natural uranium fuels for heavy water moderated reactors. Also, the quality of produced nuclear wastes can be improved significantly compare to natural uranium fuel because they contain less minor actinides.