BWR and PWR
All commercial nuclear reactors in Japan are LWRs, which are further categorized into two types, the boiling water reactor (BWR) and the pressurized water reactor (PWR), according to differences in the steam generating mechanism.
The advanced BWR is the result of the continuing evolution of the BWR, incorporating state-of-the-art technologies and many new improvements based on an extensive accumulation of world wide experience through design, construction, and operation of BWRs.
ABWR adopted Reactor Internal Pump(RIP),instead of Reactor Coolant Re-circulation Pump in conventional BWRs. This RIP eliminates re-circulation piping outside Reactor Pressure Vessel (RPV), resulting in improvement in operability and safety.
This also enables the center of gravity of the reactor building to be lowered, making the building more resistant against earthquakes.
The integration of the Reinforced Concrete and Containment Vessel (RCCV) and reactor building has increased resistance against deformation.