July 25, 1966 — Japan Atomic Power Co.'s nuclear plant in Tokai, Ibaraki Prefecture, starts commercial operations.
March 14, 1970 — Reactor 1 at Japan Atomic Power Co.'s power plant in Tsuruga, Fukui Prefecture, starts up.
April 30 to May 4, 1970 — The two reactors halt for checks.
Dec. 8, 1995 — Japan Atomic Energy Agency's Monju prototype fast-breeder reactor has a sodium leak and fire.
March 31, 1998 — Tokai plant ends commercial operations.
Sept. 30, 1999 — Two workers, violating safety rules, die in Japan's first criticality accident at a nuclear fuel processing plant in Tokai.
Aug. 29, 2002 — Tepco is found to have hidden nuke plant defects.
Aug. 9, 2004 — A never-checked pipe bursts at reactor 3 of Kansai Electric's Mihama plant, scalding five workers to death.
March 15, 2006 — Hokuriku Electric Power Co. starts up reactor 2 at its Shika plant in Ishikawa Prefecture, bringing the number of commercial reactors in Japan to a record-high 55.
July 16, 2007 — Powerful earthquake halts Tepco's Kashiwazaki-Kariwa plant in Niigata Prefecture.
Jan. 30, 2009 — Reactors 1 and 2 at Chubu Electric Power Co.'s Hamaoka plant in Shizuoka Prefecture end commercial operations.
March 11, 2011 — Tohoku megaquake-triggered tsunami cripple Tepco's Fukushima No. 1 plant, leading to three meltdowns.
April 13, 2012 — The government pushes for the restart of reactors 3 and 4 at Kepco's Oi plant to prevent a power shortage.
April 20, 2012 — With the declaration that four reactors at Fukushima No. 1 are defunct, the nation's commercial reactor inventory drops to 50.
May 5, 2012 — Hokkaido Electric halts reactor 3 at its Tomari plant for regular checks, leaving Japan without atomic power output.