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

世界上几乎所有运行的反应堆（包括民用和军用）都是基于20世纪50年代首次开发的轻水冷却系统。虽然在这段期间，这些措施已得到优化，但人们认识到，进一步改进的余地有限。因此，最近对可以在安全性、经济性和可持续性方面提供显著改进的系统（所谓的第四代系统）的研究集中在替代反应堆设计上。与此同时，对海洋来源的温室气体排放的关切重新引起了人们对商业航运使用核推进的兴趣。对于这种应用特别感兴趣的系统是熔盐反应堆，尤其是因为它采用了低压流体系统，该系统可以提供更高的安全性，同时降低设备的资本成本和重量。然而，对这种系统的分析是具有挑战性的，尤其是因为在它们的“常规”形式中，燃料包括含有裂变材料的多组分盐，该裂变材料循环通过反应堆堆芯并且随后在再次进入堆芯之前通过热交换器。对这种系统的分析要求进行反应堆物理和热工水力耦合分析，而这一点迄今难以实现。该项目将以燃料和反应堆研究小组以前在这一领域开展的工作为基础，并将侧重于进一步开发分析模型，以探索两种“常规”MSR的性能（即流体燃料）和“简化”的MSR（例如，分离的燃料和冷却剂盐），包括反应性控制系统的设计（棒、可移动的BP等），研究了连续和间歇裂变产物排出对堆芯性能的影响。如果时间允许，研究采用HTR设计的固定燃料元件（即嵌入压块中的TRISO颗粒）的混合MSR设计的相对性能，并比较两种系统在船舶推进应用中的相对优点，也将是有趣的。预计在初步研究阶段之后将确定具体的研究目标。

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.