OPTIMIZATION OF MOX ENRICHMENT DISTRIBUTIONS IN TYPICAL LWR ASSEMBLIES USING A SIMPLEX METHOD-BASED ALGORITHM

摘要

The enrichment distributions within Light Water Reactor (LWR) fuel assemblies are optimizedrnusing a modified linear programming (SIMPLEX Method) technique initiated from a flatrnenrichment distribution until a target, maximum local power peaking factor is achieved. Thernoptimum rod enrichment distribution when each rod is allowed to have its own individualrnenrichment (for this case the target, maximum local power peaking factor is 1.0) is obtained at anrnintermediate point of the optimization procedure. Later, the optimal locations and values for arnreduced number of rod enrichments (groups) are obtained for an input target maximum localrnpower peaking factor by applying sensitivity to change techniques. After an initial set ofrnenrichment groups have been defined, interchanges of rods among neighboring groups are carriedrnout to obtain the final assembly enrichment distribution. The optimization procedure isrndemonstrated by presenting results for both Boiling Water Reactor (BWR) and PressurizedrnWater Reactor (PWR) fuel assembly designs. Reactor-grade plutonium (with a fissile Pu fractionrnof 59.6%) and weapons-grade plutonium (with a fissile Pu fraction of 94.0%) were assumed to bernthe feed Pu material for the MOX fuel rods in the BWR and PWR examples, respectively. Hotfull-rnpower-temperature and beginning-of-life conditions were also assumed in the examplernproblems.