Thorium Fuel Cycle for a Molten Salt Reactor: State of Missouri Feasibility Study

Abstract

This paper was generated as part of a course on advanced nuclear fuel cycles supported through a curriculum development grant from the Nuclear Regulatory Comission. The course was graduate level and required a research component. The students in the course chose the topic of “Thorium Fuel Cycle for a Molten Salt Reactor: State of Missouri Feasibility Study.” The study consisted of developing a primer to be shared with interested parties in the nuclear community and the state. This paper was generated from this research study and the approach students took towards synthesizing the primer are annotated throughout. The thorium fueled molten salt reactor concept is one of the most promising nuclear reactor designs currently being studied, but mostly outside of the United States. Thorium reactors are desirable due to the high availability of naturally occurring fuel. However, in order for thorium fuel to be a viable alternative to uranium, a harmonious relationship between the reactor physics and molten fluoride salt transport medium must be fully understood. Chief among these technological hurdles is the use of continuous processing of spent fuel to remove fission products while the reactor is online [1] . The voluminous literature on molten salt reactors mostly dates to the 1960s era. Notably, in the U.S. the Molten Salt Reactor Experiment at Oak Ridge National Laboratory was an 8 MW(th) reactor that was designed primarily to study the technical feasibility and safety of using a molten salt based fuel and coolant. In addition to demonstrating the practicality of a molten salt reactor, the Molten Salt Reactor Experiment also addressed issues of on-line refueling, fuel makeup, and salt chemistry. Towards the end of the Molten Salt Reactor Experiment, and continuing after its shutdown, research efforts focused on techniques for separation of waste products, namely protactinium [2] . Given the prevalence of uranium based technology in the military at the time and as a matter of politics, there was little desire in the U.S. to fund nuclear research that did not provide a direct defense-related benefit. Today, as we aspire as an industry to reduce nuclear proliferation and build safer reactors, research efforts have shifted towards reducing the amount of 235 U available, particularly highlyenriched uranium. Current power reactors use low-enriched uranium ( 235 U content of less than 4.95%). In addition to the benefits of avoiding uranium enrichment, thorium for nuclear power production is also supported by a growing demand for clean energy both in the U.S. and abroad. Internationally, research in thorium fuels and molten salt reactors is underway in Japan, India, China, France and to a lesser extent, the United States. Presently, international research is needed in the development of molten salt reprocessing technology to allow for the active removal of wastes from the fuel stream, while simultaneously replenishing the fuel supply. This online fuel recycling technology could lead to a significant advantage over uranium based reactors such that a fluid fuel stream allows the reactor to be continuously re-fueled, thereby significantly reducing reactor shutdown time. Given the future economic aspirations of the nation, and in particular the state of Missouri, it is difficult to ignore the potentially huge impact of a new thorium based economy. The expansion of current mining facilities in Missouri to extract thorium could easily be achieved as thorium is present in the waste products of several mining operations already throughout the region. Moreover, the central and strategic location of the state of Missouri along the Mississippi River naturally postures the state into being a major shipping point and railway center for mineral exports. Intrastate mining, utilities, engineering, and construction companies could benefit significantly from an establishment of a thorium industry. Missouri is perfectly poised geographically, economically and academically to nurture next generation technologies for energy independence of the state and the nation as a whole.