Reactor physics analysis of Molten Salt Reactor systems for application to civilian marine propulsion

Almost all operating reactors in the world (both civil and military) are based on light-water cooled systems that were first developed in the 1950s. Although these have been optimised over the intervening period, it is recognised that the scope for further improvements is limited. Consequently, recent research into systems that could offer significant improvements in safety, economics, and sustainability (so- called Generation-IV systems) has focused on alternative reactor designs. At the same time, concern over greenhouse gas emissions from maritime sources has renewed interest in the use of nuclear propulsion for commercial shipping. A system of particular interest for such applications is the Molten Salt Reactor, not least because it employs a low-pressure fluid system that could offer increased safety whilst reducing both the capital cost and the weight of the plant. However, the analysis of such systems is challenging, not least because in their "conventional" form, the fuel comprises a multi-component salt containing the fissile material that circulates through the reactor core and subsequently through heat exchangers before entering the core again. The analysis of such systems calls for coupled reactor physics and thermal-hydraulic analyses, which have hitherto been difficult to implement.

The project will build on previous work in this area conducted within the Fuels and Reactors Research Group, and will focus on further developing analytical models to explore the performance of both "conventional" MSRs (i.e. fluid fuel) and "simplified" MSRs (e.g. separate fuel and coolant salts) under both steady-state and off-normal conditions, including the design of reactivity control systems (rods, removable BPs, etc.), and an investigation into the effects on core performance of continuous and intermittent fission product removal. If time permits, it would also be interesting to investigate the relative performance of a hybrid MSR design that employs fixed fuel elements of the HTR design (i.e. TRISO particles embedded in compacts), and to compare the relative merits of the two systems for marine propulsion applications. It is expected that specific research goals will be set following the initial period of research.