Use of thorium in light water reactors

Thorium-based fuels can be used to reduce concerns related to the proliferation potential and waste disposal of the conventional light water reactor (LWR) uranium fuel cycle. The main sources of proliferation potential and radiotoxicity are the plutonium and higher actinides generated during the burnup of standard LWR fuel. A significant reduction in the quantity and quality of the generated Pu can be achieved by replacing the ²³⁸U fertile component of conventional low-enriched uranium fuel by ²³²Th. Thorium can also be used as a way to manage the growth of plutonium stockpiles by burning plutonium, or achieving a net-zero transuranic production, sustainable recycle scenario. This paper summarizes some of the results of recent studies of the performance of thorium-based fuels. It is concluded that the use of heterogeneous U-Th fuel provides higher neutronic potential than a homogeneous fuel. However, in the former case, the uranium portion of the fuel operates at a higher power density, and care is needed to meet the thermal margins and address the higher-burnup implications. In macroheterogeneous designs, the U-Th fuel can yield reduced spent-fuel volume, toxicity, and decay heat. The main advantage of Pu-Th oxide over mixed oxide is better void reactivity behavior even for undermoderated designs, and increased burnup of Pu.