It is the largest nuclear generating station in the world by net electrical power rating. It was approximately 15 miles from the epicenter of the second strongest earthquake to ever occur at a nuclear plant, the Mw 6.6 July 2007 Chūetsu offshore earthquake. This shook the plant beyond design basis and initiated an extended shutdown for inspection, which indicated that greater earthquake-proofing was needed before operation could be resumed.
The plant was completely shut down for 21 months following the earthquake. On May 9, 2009, one unit (Unit 7) was restarted, after seismic upgrades. Units 6, 1, and 5 have since been restarted as well.
Reactor attributes
| KK - 1 | KK - 2 | KK - 3 | KK - 4 | KK - 5 | KK - 6 | KK - 7 |
|---|
| Reactor Type | BWR | BWR | BWR | BWR | BWR | ABWR | ABWR |
| Net Power (MW) | 1,067 | 1,067 | 1,067 | 1,067 | 1,067 | 1,315 | 1,315 |
| Gross Power (MW) | 1,100 | 1,100 | 1,100 | 1,100 | 1,100 | 1,356 | 1,356 |
| Start of Construction | 6/5/1980 | 11/18/1985 | 3/7/1989 | 3/5/1990 | 6/20/1985 | 11/3/1992 | 7/1/1993 |
| First Criticality | 12/12/1984 | 11/30/1989 | 10/19/1992 | 11/01/1993 | 7/20/1989 | 12/18/1995 | 11/01/1996 |
| Commission date | 9/18/1985 | 9/28/1990 | 8/11/1993 | 8/11/1994 | 4/10/1990 | 11/7/1996 | 7/2/1997 |
| Installation Costs (1,000 yen/kW) | 330 | 360 | 310 | 310 | 420 | 310 | 280 |
| Reactor/NSSS Supplier | Toshiba | Toshiba | Toshiba | Hitachi | Hitachi | Hitachi/Toshiba/GE | Hitachi/Toshiba/GE
|
Fuel
All reactors continue to use low-enriched uranium as the nuclear fuel; however, there have been plans drafted by Tepco to use MOX fuel in some of the reactors by the permission of the Japanese Atomic Energy Commission (JAEC).
