Next generation nuclear plant (NGNP) project - Preliminary assessment of two possible designs

The analytical evaluations of a prismatic fuel type helium gas-cooled reactor and a pebble-bed fuel helium gas reactor, the versions of Next Generation Nuclear Plant (NGNP) project were presented. Sensitivity calculations to determine the power to determine the power that could be obtained for different core heights, were performed. It was estimated with a coolant inlet temperature of 490 °C and 10% nominal core bypass flow that the peak power for a 10-block-high core is 686 MWt, for a 12-block-high core is 786 MWt, and for a 14-block core is 889 MWt. It was observed by the core neutronics calculations that the NGNP exhibit strongly negative Doppler and isothermal temperature coefficients of reactivity over the burnup cycle.