Rethinking the Thorium Fuel Cycle: an Industrial Point of View

Abstract

The use of thorium as a fertile material in combination with a fissile material (either U233, U235 or plutonium) as an alternative to the uranium fuel cycle received a great deal of attention in many venues from the 1950s to the mid 70s. More recently, new studies have been carried out on this cycle for transmutation purposes and several countries such as India still continue to consider the thorium cycle as an attractive option within the framework of their national nuclear programs. The purpose of this paper is to provide an updated overview of the potential of the thorium cycle, taking into account the renewed interest in the development of nuclear energy as currently under consideration for future energy systems. In this paper many of the issues related to the use of thorium at each stage of the nuclear fuel cycle are reviewed from the standpoint of industrial feasibility and economy. First, past experience with using thorium as a fuel for prototype or commercial nuclear reactors, particularly in high temperature reactors, is examined. The neutronic and physic aspects of the thorium in various reactors will be overviewed. Second, updated data on world-wide thorium resources and supplies is presented. Then, the sustainability issues of nuclear energy development with regard to the future availability of natural resources (uranium and thorium) are addressed. After that follows a discussion of the pros and cons of radiological/ nuclear/chemical characteristics of thorium as it relates to the implementation of fuel cycle industrial processes and impacts on the wastes. In particular, the technical aspects of back end fuel cycle issues are examined for both open and closed fuel cycles including reprocessing and recycling technical issues. Also examined are proliferation issues related to the use of the thorium cycle. Accompanying this examination is a comprehensive analysis of the technical features of various thorium fuel cycle options from the standpoint of proliferation resistance. Finally, economical aspects of the thorium fuel cycle are addressed. In summary, these analyses permit the reader to draw some general conclusions regarding the use of the thorium cycle for the development of a sustainable nuclear energy system.