CALCULATION OF AXIAL FLUX DISTRIBUTION IN CANDU FUEL BUNDLES

摘要

A knowledge of axial flux distributions in various CANDU fuel bundle designs is necessary for their proper evaluation. In particular, the peaking of the flux near the ends of the elements is an important factor in the determination of a reactor's critical power ratio. The experimental procedure for measuring flux distributions is costly and time-consuming, so a reliable computational method should prove a valu-able design tool. In cases where a two-dimensional (2-D) representation is adequate to describe the bundle geometry, acceptable results could be expected from an application of the discrete-ordinates method. However, many designs will not allow so simple a geometrical model making it nec-essary to resort to a 3-D calculation. The application of Monte Carlo methods to the problem is not straightforward, because of an extremely high variance in the estimate of thermal-flux distribution. In the present report the discrete-ordinates method is compared with experiment for a fuel bundle which admits a 2-D representation, and a method is presented for dealing with designs requiring a 3-D calculation. The latter method is compared with experiment for a bundle with staggered plenums.