Molten Salt Nuclear Reactors: A Comparative Assessment of the Resource Requirements and Proliferation-Risk Attributes of Single-Fluid and Dual-Fluid Denatured Designs

Abstract

Molten salt reactors were first proposed as an alternative to solid-fueled light water reactors at Oak Ridge National Laboratory (ORNL) in the 1950's. Although the designs showed promising features such as greatly reduced uranium requirements and waste production, and did not suffer from any fundamentally prohibitive technology barrier, the program was canceled due to lack of Government funding. This paper reconsiders the use of denatured molten salt reactors (DMSRs) as a source of clean, carbon-free electricity in the future. Monte Carlo and nuclear burn-up codes are used to evaluate two different DMSR designs as candidates to be widely deployed around the world as small modular reactors. ORNL's single-fluid DMSR design is benchmarked and evaluated using modern neutron cross section libraries. Characteristics such as fuel requirements, waste production, and proliferation risk are assessed. A new, two- fluid DMSR is designed as an alternative to the single-fluid DMSR with the hopes of determining whether the improved fuel effciency of the two-fluid design is worth the added complexity and proliferation risk. Both the single-fluid and two- fluid DMSR designs were found to offer superior performance to traditional light water reactors. Although the two- fluid DMSR designed here does offer superior fissile-effciency when compared to the single- fluid design, much work remains to be done to determine whether its problems, particularly the problem of uranium saturation in the fuel salt, could be overcome. The single-fluid DMSR design is particularly well suited for the role of small modular reactor due to its low fuel consumption and high level of proliferation resistance. It is recommended that serious research resume on molten salt reactors since they have the potential to greatly improve upon the negative attributes of traditional light water reactors and could become a valuable source of carbon-free electricity in the future.