is a shortened reference for the full titles shown in the previous footnote. Control Element(s): Object(s) employed to interact with an MSR's neutron population to adjust reactivity. Control elements can act through fuel displacement, neutron absorption, neutron reflection, neutron spectral adjustment, or a combination of these methods. Control elements can be solids, liquids, or gases, and they can be passively or actively positioned.
Emergency Cooling System:System that provides decay heat removal from the Reactor Fuel following an accident (e.g., a direct reactor auxiliary cooling system or a reactor vessel auxiliary cooling system).Fission Product Barrier: Portion of the Fuel System Boundary in contact with fission products only (e.g., the gas management system boundary).Fuel Barrier: Portion of the Fuel System Boundary in contact with the fuel salt (principally the Vessel, heat exchanger, control element thimbles, instrumentation thimbles, piping, tanks, and valves).Fuel System Boundary: All structures that prevent the release of fuel, fission gas, or other fission products. For an MSR, this includes the Vessel, waste-handling tank, pumps, valves, and piping. (Essentially includes the Fission Product Barrier and the Fuel Barrier.) Heat Dissipation System: Set of components or system(s) that interface with the Primary Cooling System to provide the principal means of transferring the heat from the core to the environment. The Heat Dissipation System might use a variety of coolants (e.g., salt, liquid metal, or water) but does not contain fuel.
Neutron Moderator:In an MSR, materials in or near the core that consist of light elements. Moderators are generally solid form.Primary Cooling System: Directly interfaces with the Fuel System Boundary at the fuel salt/primary cooling system heat exchanger(s) to provide the principal means of removing heat from the fuel salt by transferring the heat to the Heat Dissipation System. The Primary Cooling System typically contains a salt but does not contain fuel.Reactor Fuel: In an MSR, fuel salt which consists of fissionable and possibly fertile halide salts, fission products, and generally solvent halide salt(s).Vessel: For an MSR, structure containing the Active Reactor Core. Other components might reside in the Vessel but outside the Active Reactor Core, such as heat exchangers in certain design configurations.