Minimum assembly reload system optimization for LWR's

The MARS (Minimum Assembly Reload System) concept minimizes the number of fresh fuel assemblies required at BOC (beginning of cycle) fuel reloading. The MARS concept determines the optimal reload batch size both during normal equilibrium cycle operation and after a perturbation to the equilibrium cycle. Therefore, MARS provides optimal system recovery after a cycle perturbation such as a coastdown derating. The MARS concept employs two principle modes of optimization. The first mode utilizes linear programming (LP) to minimize the reload batch size subject to ten system constraints covering material balances, reactivity, and power peaking. The LP algorithm therefore determines the value of the objective functional and the suggested region-wise fuel shuffling policy. The results of the LP optimization necessarily requires the exercise of a relatively high degree of engineering judgment in the placement of individual fuel assemblies. Therefore, the first mode is followed by the second mode of optimization which uses a form of direct search (DS) to discover the optimal fuel assembly placement that avoids excessive BOC power peaking and excessive EOC discharge burnup while maintaining system criticality. Although the LP model uses one-dimensional, one group neutron diffusion theory, the DS model uses two-dimensional, modified one group neutron diffusion theory. Consequently, the optimization terminates with the DS algorithm and provides the optimal X--Y coordinates of each fuel assembly