The safety design of the Toshiba Boiling Water Reactor (TOSBWR) was created ∼8 yr ago. The design concept is intermediate between conventional boiling water reactors (BWRs) and the advanced BWR (ABWR). It utilizes internal pumps and fine motion control rod drive, but the emergency core cooling system (ECCS) configuration is different from both conventional BWRs and the ABWR. The plant output is 1350 MW(electric). The design is based on two important philosophies: the positive cost reduction philosophy and the constant risk philosophy. The former aims to improve the cost-effectiveness of safety design; the latter seeks a uniform distribution of plant risk. To implement these two philosophies, the TOSBWR safety design utilized system subdividing and probabilistic risk assessment insights. Because of these philosophies, the TOSBWR safety design has combined large cost reductions with safety improvements. The core damage frequency due to multiple failures is reduced about one order of magnitude compared with conventional BWRs, while the capacity of the low-pressure ECCS is reduced to ∼60% of that of the conventional BWR5.