Katsumasa Haikawa

Improvements in boiling water reactor uranium utilization and operating experience with burnup increase

A boiling water reactor (BWR) core design for better uranium utilization is presented, and its validity is demonstrated through simulation and operation data. Together with the axial power flattening obtained by an axially zoned enrichment core, uranium utilization improvement techniques such as an axial blanket for neutron leakage reduction, a low leakage loading pattern, an improved local enrichment distribution in the fuel bundle, and spectral shift operation method are promising design features to be applied to the BWR core. Quantitative studies for the amount of burnup increase and power peaking rise are made to estimate a level of effective uranium utilization. The improvements in uranium utilization are confirmed not only in the computational core design study, but also in empirical data from a commercial BWR. Operating experience proves the adequacy of the core design. A uranium utilization improvement of >10% is obtained without a loss of load factor.