Performance optimization of the CANDLE reactor for nuclear energy sustainability

Constant axial shape of neutron flux, nuclide densities and power shape during life of energy producing (CANDLE) fast reactors show the following outstanding merits: (1) simple and safe, (2) high performance to nuclear nonproliferation and safeguard, (3) small volume of waste, (4) efficient fuel use. However, CANDLE reactor has two inherent problems: (1) destruction of cladding integrity caused by high fast neutron dose and high accumulated FP gas pressure and (2) longer core height caused by the shape of burning region and shift of the region along burning. In the present paper cladding integrity is tried to be kept by employing recladding and the core height is tried to be shorten by employing multi-channel once-through-then-out (MOTTO) cycle. MOTTO cycle adjusts the amount of discharged fuel for each pin to make the axial power peak align perpendicular to the core axis at the beginning of each cycle operation. We selected a LBE cooled fast reactor with nitride fuel for the present study. Thermal power rate is 1540 MW. The core-plus-blanket diameter is 4 m, and the height is minimized to be 1.6 m. It is similar to familiar pancake-type fast reactor designs and considered to be economically feasible together with other many cost effective characteristics.