Parametrisation for optimisation of reload patterns for boiling water reactors

Parametrisation of reload patterns for BWRs is attempted for the purpose of optimising them. This is done in two stages. The first stage involves an algorithm for constitution of a reload pattern out of a given set of fuel bundles. It is designed to constitute patterns with features of Low Leakage Loading (LLL) and checker board arrangement of fresh and exposed fuel bundles in the central region. The characteristics of the Reload Patterns can be manipulated by means of only two input parameters. The idea of the dependence the Haling power peaking and the cycle energy of the ''Biparametric Reload Patterns (BRP)'' on the two input parameters is presented through case studies. The idea of the ranges of these characteristic quantities and their mutual relation is given by the case studies both for general as well as the optimum BRPs. A preliminary optimization procedure for biparametric reload patterns is presented. This method is augmented by a multi-parametric algorithm to reshuffling the radial exposure distribution interactively so as to exhaust any possibility of improvement in a given reload pattern. When tested against this procedure, the optimum biparametric reload patterns are seen to provide only a limited scope for improvement showing that they are very close to the optimum reload patterns. The extent of possible improvement is illustrated. The entire procedure is incorporated in a 2-dimensional code CORECOOK. The computer time needed for this task of optimisation of reload pattern is comparable to that required for one routine 3-D core follow-up calculation. This algorithm has been used for obtaining the reload patterns for all the five cores loaded in BWRs at Tarapur (India) since 1988. (author). 25 refs, 5 figs, 2 tabs