MSR system 400 includes dynamic neutron reflector assemblies 406. Operating temperatures of MSR system 400 may be high enough to liquefy a variety of suitable neutron reflector materials. For example, lead and lead-bismuth melt at approximately 327° C. and 200° C., respectively, temperatures within the operating range of the reactor. In an implementation, dynamic neutron reflector assemblies 406 are configured to contain a flowing and/or circulating fluid-phase of the selected neutron reflector materials (e.g., lead, lead-bismuth, etc.). In FIG. 4, solid tip arrows indicate the flow of neutron reflector material. Dynamic neutron reflector assemblies 406 may be formed from any suitable temperature and radiation resistant material, such as from one or more refractory alloys, including without limitation one or more nickel alloys, molybdenum alloys (e.g., a TZM alloy), tungsten alloys, tantalum alloys, niobium alloys, rhenium alloys, silicon carbide, or one or more other carbides. In an implementation, dynamic neutron reflector assemblies 406 are positioned on, and distributed across, the external surface of the reactor core section. In implementations, the dynamic neutron reflector assemblies 406 may be segmented, as explained above with reference to FIG. 3. In an implementation, dynamic neutron reflector assemblies 406 are arranged radially across the external surface of the reactor core section. Dynamic neutron reflector assemblies 406 may be arranged to form a contiguous volume of neutron reflector material around the reactor core section. Any geometrical arrangement and number of dynamic neutron reflector assemblies 406 is suitable for the technology described herein. For example, dynamic neutron reflector assemblies 406 may be arranged in a stacked ring configuration, with each module filled with a flow of neutron reflector material to form a cylindrical neutron reflecting volume around the reactor core section. Dynamic neutron reflector assemblies 406 may also be arranged above and below the reactor core section.
