Investigation of different scenarios of thorium-uranium fuel distribution in the VVER-1200 first core

Thorium fuel gives some superiority from safeguards point of view and is now being considered as an option for nuclear fuel. It is found to achieve high proliferation resistance because it has significant lower production of plutonium and minor actinides as compared with uranium fuel. The effect of the insertion of thorium, as a part of the nuclear fuel, on the neutronic parameters of the VVER-1200 first core under normal operation was studied. Two different patterns, namely mixed thorium uranium fuel and seed-blanket fuel, were compared. In addition to the amount of the inserted thorium, it was found that the position of the thorium assemblies inside the reactor core plays an important role in determining the effective multiplication factor and hence the core cycle length. It was concluded that the best location of thorium is in the periphery of the reactor core. As the preparation of thorium fuel does not involve all the requirements imposed by the uranium fuel, it is therefore expected that the economical feedback of both uranium-thorium fuels will be also positive, especially for a country with high thorium abundance.