Preliminary Design And Analysis Of Shim Rod Assembly For Lead Bismuth Eutectic Cooled Reactor

As an innovative reactor system, lead-based reactor use lead-based alloy as the coolant and have high neutron, high transmutation capability, high heat-transfer ability and high safety. These characteristics make lead-based reactor a promising concept for the future. In lead-based reactors, the shim rods deal with the majority reactivity and has a considerable impact on the reactor safety.Based on the high density and high buoyancy service condition caused by the Lead Bismuth Eutectic (LBE) and the international design experience of shim rods for LBE cooled reactor, the design requirements and criterions were discussed, which cover aspects such as reactivity control, structure stress and thermo hydraulics. A shim rod assembly scheme which satisfied the service condition and design requirements and criterions was proposed based on the former discussion. The scheme applies gravity scram which can assure the reactor can be shut down during loss of coolant accident. And the scheme applies airtight structure. The main components of the shim rod assembly includes absorber bundle, bundle tong, ballast, inner wrapper, dowel steel, inner wrapper cover and outer wrapper. The main structure parameters of the components in shim rod assembly were analyzed and studied through the neutronics analysis such as steady state critical calsulation, the burn up calculation both with the structural design and stress calculation. The optimal preliminary structure schemes of the components were carried out. And the feasibility of the shim rod assembly scheme was verified. The shim rod scheme can fairly well solve the impacts imposed by the ballast to the assembly and other componets. That means that the shim rod can effectively deal with the buoyancy while at the sametime keep its integrity and serve the intended task.The reaserch of the lead-based reactor shim rod design work may be referenced by the design of other two control rod, the safety rod and the regulating rod. The work in this paper provides foundation for the further work.