Evaluation of nuclear core performance of the gas-cooled fast breeder reactors

Nuclear core performance of the gas-cooled fast breeder reactors with power 1000MWe, helium-cooled pin type fuel and coated particle fuel respectively, has been investigated mainly in breeding performance, also comparatively with the sodium-cooled fast reactor of relatively high breeding ratio designed in JAERI. Two-dimensional burnup code APOLLO based on diffusion approximation and JAERI-Fast 25 group neutron cross-section set were used for calculation. The pin type fuelled gas-cooled fast reactor has possibility of a short doubling time due to the high breeding ratio and long fuel dwelling, while there are some problems including large fissile inventory and comparatively low power density. The coated particle fuelled gas-cooled fast reactor is inferior in breeding performance to the pin type fuel gas-cooled or the sodium-cooled fast reactor, because of the low core conversion ratio. (auth.)