Boiling water reactor loading pattern optimization using simple linear perturbation and modified Tabu search methods

An automated system for designing a loading pattern (LP) for boiling water reactors (BWRs) given a reference LP and control rod (CR) sequence has been developed. This system employs the advanced nodal code SIMULATE-3 and a BW R LP optimization code FINELOAD-3, which uses a simple linear perturbation method and a modified Tabu search method to select potential optimized LP c andidates. Both of these unique methods of FINELOAD-3 were developed to ach ieve an effective BWR LP optimization strategy and to have high computation al efficiency. FINELOAD-3 also adjusts deep CR positions to compensate for the core reactivity deviation caused by fuel shuffling. The objective funct ion is to maximize the end-of-cycle core reactivity while satisfying the sp ecified thermal margins and cold shutdown margin constraints. This optimiza tion system realized the practical application for real BWR LP design. Comp uter time needed to obtain an optimized LP for a typical BWR/5 octant core with 15 depletion steps is similar to4 h using an engineering workstation. This system was extensively tested for real BWR reload core designs and sho wed that the developed LPs using this system are equivalent or better than the manually optimized LPs.