Safety Analysis of BWR-HD: An Optimized Boiling Water Reactor with High Power Density

An optimization search over all design parameters yields a boiling water reactor (BWR) with high power density (BWR-HD) at a power level of 5000 MW(thermal), equivalent to a 26% uprated Advanced BWR (ABWR), the latest version of operating BWR. This results in economic benefits, estimated to be [approximately]20% capital and operation and maintenance costs and similar total fuel cycle cost per unit electricity. A safety analysis of the BWR-HD was performed and compared with that of the ABWR. It covered a range of transients, involving a decrease in reactor coolant inventory or coolant system flow rate, changes in coolant temperature along with increase in reactor pressure, and a reactivity-initiated transient. The BWR-HD's different core flow velocity, feedwater flow rate, core inlet temperature, void coefficient of reactivity, pressure drop, core fuel loading, and volume of fluid in the core resulted in very different response to transients. In general, the 1.3-m-shorter core results in faster scram times and lower total positive reactivity insertions during the transients, which improves the BWR-HD's performance compared to that of the ABWR. The core remains covered and the pressure in the reactor pressure vessel never rises above the licensing limits during any of the simulated transients. The change in minimum critical power ratio for the BWR-HD was smaller than or equal to that of the reference ABWR in all of the six simulated transients. For the loss-of-coolant-inventory accidents and severe accidents, the BWR-HD qualitative performance was judged to be acceptable and could result in an improved response with the lower fuel and zirconium loading.