A design study on Pb-208 cooled compact CANDLE burning reactor for future nuclear energy supply

A compact pool-type Pb-208 cooled CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy producing reactor) with a thermal power rating of 125 MWth is considered for the future nuclear energy supply. Natural Pb consists of Pb-204, Pb-206, Pb-207 and Pb-208. Pb-208 has a small capture and inelastic-scattering cross-section, which makes it possible to reduce neutron capture by coolant and to make neutron spectrum harder. In case of Pb-208 coolant instead of natural Pb, the core height and radius are reduced to 1.5 m and 1 m, respectively. The effective multiplication factor of the core, keff, could be increased from keff = 0.984 of natural Pb up to keff = 1.006. For increasing natural circulation head, coolant velocities in each core zone are adjusted by orifice at the core inlet position. The reactor vessel height is equal to that of a typical loop-type demonstration FBR vessel to obtain natural circulation head.