Study on the critical mass and neutron flux distribution of coupled-core with a light-water moderator and reflector in the KUCA

A study on a light-water moderated and reflected coupled-core was carried out to investigate the critical mass and neutron flux distribution as a function of the separation distance between the two cores. The critical mass reached the minimum value in a coupled-core with an approximately 1 cm wide water gap, and the peak value of neutron flux in the water gap region became the maximum when the separation distance is around 5 cm. These data were analyzed with the SRAC system. The calculated critical mass agreed well with those of experiments within an accuracy of ∼1%. To calculate the neuron flux distribution, it was confirmed that attention should be paid to the number of energy groups and the method employed in the generation process of homogenized cross sections. It was found that the calculation can approximately reproduce the measured neutron flux distribution. (author)