Increasing the Fuel Utilization in Gen-II BWR with Reduced-Moderation Square Lattice Fuel Assemblies - 14145

Current uranium fueled Gen-II light water reactors (LWR) have an unsatisfying resource utilization of only around 1 % because of a conversion ratio below 0.6. This disadvantage can be decreased by a reduction of the neutron moderation. Most currently investigated high-conversion light water reactors (HCLWR) are quite innovative and still far from being licensed. Therefore, a less ambitious concept based on well-known square lattice fuel assemblies was suggested in the past as intermediate, more feasible step. In this paper investigations for an evolutionary low moderated boiling water reactor (BWR) fuel assembly design with square fuel rod lattice and improved fuel utilization are presented. Starting from a conventional ATRIUM^TM 10XM fuel assembly, changes were applied to fuel rod size, fuel rod pitch, lattice dimension, average enrichment and internal water structures. Additionally, the influence of different fuel compositions on the corresponding results was analyzed. For the investigations, the deterministic SCALE6.1 / TRITON lattice physics sequence was used, utilizing the NEWT transport solver, cross-section processing based on CENTRM, and user-defined Dancoff factors obtained with the module MCDancoff. ENDF/B-VII cross-sections were used for all investigations. Investigated performance parameters include the multiplication factor, the conversion ratio (CR), plutonium quality and reactivity coefficients, such as the void coefficient (VC). For one representative reduced-moderation lattice, Monte Carlo investigations with KENO-VI have been done to verify the deterministic approach and to assess the results especially for cases with high void contents. (authors)