Basic considerations are discussed in the area of LMFBR refueling optimization. The procedure of search for the optimum refueling scheme is based on a systematic enumeration algorithm embodying the heuristic rule "Elimination of Hopeless End States (EHES)". The optimization procedure thus developed reveals the global characteristics of the refueling scheme, on the basis of a macroscopic regression model which describes the burnup-dependent core performance.Sample numerical results are obtained on problems of optimizing the refueling scheme for the 4-zone zone-loaded and 2-zone scatter-loaded cores of a typical sodium cooled mixed-oxide fueled fast power reactor. Case studies are conducted on the effect of change in the elimination factor adopted in applying the EHES, in the upper or lower boundaries of constraints, in the performance criterion, and in various parameters governing the mode of reactor operation such as the duration of one cycle period. The study has revealed several notable characteristics particular to LMFBR core refueling, such as the common trait of optimized refueling schemes for 2-region cores of repeated identical refueling patterns, and incompatibility between radial power flattening and sustained useful life for the core.
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