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The Difference for Proliferation Resistant and Physical Protection (PRPP) Concept for Liquid-Fueled Reactor
Molten salt reactor (MSR) has a unique characteristic using liquid fuel and/or coolant salt among six type of GEN IV reactors. Liquid fuels and on-site processing are fundamentally different from a solid fuel reactor where separate facilities produce the fresh solid fuel and process the Spent Nuclear Fuel. Because the choice of fuel cycle affects the safeguards and non-proliferation characteristics of the reactor system, different MSR concepts may have different proliferation resistance and physical protection characteristics. For example, MSR design variants that use solid fuel but are cooled with liquid salts such as FHR are very close to the Very High Temperature Reactor design concept. The composition of various fuel salts is a representative factor that makes it difficult to generalize the PRPP evaluation principle of MSR. In addition, the flow of molten salts containing fissile materials is also complex depending on the design of the reactor. The path through which radioactive materials travel not only inside the reactor but also to nuclear fuel cycle facilities can act as a difficult factor in measuring nuclear materials. As a further complication, some of the plants include fuel salt drain tanks intended to provide decay heat removal while others are designed to provide decay heat removal while the salt is maintained within the reactor vessel. Some lessons learned from the prior molten salt breeder reactor program are reflected in all of the new designs. Interior reflectors/shielding are frequently employed to reduce the radiation damage to the reactor vessel, and fuel salt chemistry control is employed to substantially limit oxidizing the container alloy constituents. However, even with the vessel interior shielding, the containment environment around both solid and liquid fueled MSRs during operation is likely to have substantially higher dose rates than at LWRs due to the fission process and fission products in the case of circulating liquid fueled reactors, and the shortlived activation products of fluorine (16N, 20F, and 19O) in the case of FHRs. Consequentially due to insufficient shielding from the coolant and the vessel wall, MSR containments will be remote access only for liquid fueled systems and remote access only during operation for FHRs.
