Thorium fuel cycle economics

Abstract

This thesis examines potential of thorium as a nuclear fuel for High Temperature Reactors (HTRs). It aims to analyse fuel cycle based on specific mixture of thorium and the additional fissile material. Two important contributors to the fuel cycle costs are: uranium ore price and enrichment which contribute to 75 % over the total fuel cycle costs. Reduction of U235 enrichment requirements, improved fissile fuel utilization (high conversion ratio) and enlargement of fissile resources (breeding U233 from Th) can be achieved by application of thorium fuel cycle. The need for reactors with better proliferation-resistance, longer fuel cycles, higher burn up, improved waste form characteristics, and reduction of plutonium inventories and the possibility of in-situ use of bred fissile material has led to renewed interest in thorium - based reactors. In a pebble - bed HTR the different fuel particles, Plutonium (Pu) on the one hand and Thorium (Th) and Uranium (U) on the other hand can be loaded also into different fuel elements, which are continuously loaded and disloaded. In this thesis the following fuel cycle mixtures were examined: Th-U, Th-Pu, and pure U. ThO2 and PuO2 for a pebble - bed High Temperature Reactor are in general intended to incinerate plutonium and minor actinides provided by discharged and reprocessed fuel of Light Water Reactors and to breed the new suitable fissionable material U233. I have made a comparison between the once - through and closed thorium - uranium fuel cycles. For assessment I have used a standard Present Worth Cost method. The previous fuel cycle studies conducted by E. Teuchert have shown that there are no significant differences between thorium and uranium fuel cycles costs. My calculations have shown similar results. The parameters can be optimized in the reactor design favourably for both fuel cycles pure uranium and thorium mixed with uranium or plutonium