Generation III reactors, or Gen III reactors, are a class of nuclear reactors designed to succeed Generation II reactors, incorporating evolutionary improvements in design. These include improved fuel technology, higher thermal efficiency, significantly enhanced safety systems (including passive nuclear safety), and standardized designs intended to reduce maintenance and capital costs. They are promoted by the Generation IV International Forum (GIF).
The first Generation III reactors to begin operation were Kashiwazaki 6 and 7 advanced boiling water reactors (ABWRs) in 1996 and 1997. From 2012, both have been shut down due to a less permissive political environment in the wake of the Fukushima nuclear accident. Due to the prolonged period of stagnation in the construction of new reactors and the continued (albeit declining) popularity of Generation II/II+ designs in new construction, relatively few third generation reactors have been built.