AB1600—Progress of ABWR technology toward next generation ABWR

Advanced boiling water reactor (ABWR) plants have achieved an excellent operating performance since the first ABWR plant started its commercial operation in 1996. Based on the ABWR technology, progress has been made towards a next generation ABWR, AB1600 in Toshiba. The AB1600 plant aims at meeting the demand for the replacement of the current BWRs, which is expected to be realized by 2020 and beyond. In the AB1600 design, therefore, further improvements in economic and reliability aspects have been pursued by incorporating several new technologies. The reactor power is uprated to 1600 MWe from 1350 MWe of the first ABWR plant in order to benefit from economy of scale. A large fuel assembly with high power density is adopted in order to reduce both of the capital cost and maintenance cost associated with refueling by decreasing the number of fuel assemblies and control rod drives. The AB1600 safety system design employs a hybrid safety system, which consists of both active and passive systems for the design basis and the beyond-design basis accidents, to enhance the safety of the plant. As a countermeasure against severe accidents, the passive systems for the functions of decay heat removal, coolant injection and molten core debris cooling are incorporated.