[en] A statistical model of a fuel element cluster considering the laws of channel flow section distribution obtained in experiments at the BN-600 reactor fuel assembly mock-up is suggested. Technique for calculating the fuel assembly temperature field based on the sequential calculation of a set of fuel assembly versions taking into account the interchannel heat and mass transfer is described. Variants of channel flow section distribution formed by fuel elements are realized using the Monte-Carlo method according to the given function of channel flow section probability density. As a result of the calculations statistical distributions of temperature increase in channels without account for the interchannel heat and mass transfer and with it are obtained. The effect of interchannel transfer on the reduction of maximum nonuniformity in coolant temperature increase caused by dispersion of channel flow sections is shown. The conclusion is made that if heat and mass transfer is not taken into account the value of coolant temperature increase in separate channels coincides with limited value obtained by the dispersion method