The present study exposes a feasibility analysis for a nuclear reactor shutdown system by means of a liquid neutron absorber. The presented system has been designed for single-fluid Molten Salt Fast Reactors (MSFR) but can be easily extended to other Molten Salt Reactor (MSR) designs and even to liquid metals (LM) reactors.

Most of the safety shutdown concepts for MSRs designs rely on their intrinsic negative temperature coefficient to make the reactor subcritical. In case of emergency, most MSRs concepts make use of the widely accepted drainage system by means of frozen plugs or other passively activated mechanisms that drive the fuel to an also passively cooled set of containers below the reactor. In this study, an alternative shutdown system is described, consisting of filling a set of pipes inside the reactor with a liquid neutron absorbing material. The system may be used as the main shutdown system, but in the present work it is studied as a complementary system to a central shutdown/control rod.

A simplified single fluid external indirect cooling MSFR model with axial and central reflectors has been used to test the system. The only purpose of this model is to check the feasibility of the system and not to show an actual working system in a reactor design. Therefore, a pre-conceptual design is presented. Several representative analyses including neutronics, hydraulics and a mechanical assessment, have been carried out to evaluate the feasibility of the concept.

This feasibility study aims to be a decided step towards a safe passive shutdown system for Generation IV (GenIV) reactors with special focus on MSRs.

本研究揭示了利用液体中子吸收器对核反应堆停堆系统进行​​可行性分析的方法。提出的系统是为单流体熔盐快堆（MSFR）设计的，但可以轻松扩展到其他熔盐反应堆（MSR）设计，甚至是液态金属（LM）反应堆。

MSR设计的大多数安全停机概念都依赖于其固有的负温度系数，使反应堆处于亚临界状态。在紧急情况下，大多数MSR概念通过冻结的塞子或其他被动激活的机制利用被广泛接受的排水系统，该机制将燃料驱动到反应堆下方的一组被动冷却的容器中。在这项研究中，描述了一种替代性的停机系统，该系统包括在反应堆内部的一组管道中填充液态中子吸收材料。该系统可以用作主要的停机系统，但在当前工作中，它是作为中央停机/控制杆的补充系统而研究的。

具有轴向和中央反射器的简化的单流体外部间接冷却MSFR模型已用于测试系统。该模型的唯一目的是检查系统的可行性，而不是在反应堆设计中显示实际的工作系统。因此，提出了前概念设计。已经进行了包括中子学，液压学和机械评估在内的几种代表性分析，以评估该概念的可行性。

这项可行性研究旨在朝着第四代（GenIV）反应堆的安全被动关闭系统迈出决定性的一步，该系统特别关注MSR。