Core Design Study of Small Transportable Long-life Lead-bismuth Cooled Fast Reactor

In order to meet the demand of power supply in remote areas, a conceptual core design of a small transportable long-life lead-bismuth cooled fast reactor (STLFR) with rated power of 20 MW was proposed to operate for 18 EFPY (effective full power years) without refueling. In order to reduce core volume, the tube-in-duct (TID) fuel was proposed with coolant inside the tubes and fuel outside, which achieved a high fuel volume fraction in the core. For radial power flattening, the active core was divided into three regions radially with different sizes of coolant tubes. In order to reduce core height, a liquid absorber control system was implemented using ⁶Li enriched liquid lithium as the neutron absorber. In order to lower the initial excess reactivity, replaceable fixed absorbers were installed in the control and scram assemblies, and then replaced by fixed reflectors at the 1/3 and 2/3 core lifetime. The thermal design constraints are satisfied during the whole life. The control system and safety system can independently provide sufficient shutdown margin. Five typical anticipated transients without scram were analyzed with the quasi-static reactive balance method, and the inherent safety characteristics of the core are demonstrated preliminarily.