Neutronic-thermal hydraulic coupling analysis of the fuel channel of a new generation of the small modular pressurized water reactor including hexagonal and square fuel assemblies using MCNP and CFX

The maximum temperature of fuel centerline in both types of the proposed SMRs is much lower than that of large PWRs (e.g., 2156 K for hot rod in VVER-1000). Between hexagonal and square fuel assemblies, the hexagonal FAs are preferred because of the two reasons; first, the axial fuel centerline temperature in the hottest hexagonal channel is lower than that of hottest square channel, so it is a good feature with respect of safety margins. Second, the outlet temperatures of the channels in the SMR core with hexagonal FAs are higher than the outlet temperature of the channels in the SMR core with square FAs. Thus the thermal efficiency of the reactor core with hexagonal FAs is more than that of the core with square FAs.