March 11, 2011 — The magnitude 9 earthquake and subsequent tsunami cause a station blackout at the Fukushima No. 1 power plant, crippling reactors 1 through 4. The government declares an emergency and orders residents living within 3 km of the plant to evacuate.
March 12 — Prime Minister Naoto Kan inspects the plant. A hydrogen explosion rips through the No. 1 reactor building. The evacuation zone is expanded to a 10-km radius and later to 20 km.
March 14 — The No. 3 reactor building suffers a hydrogen explosion.
March 15 — A hydrogen explosion occurs in the No. 4 reactor building.
March 17 — Ground Self-Defense Force helicopters drop water to cool off spent fuel rods in the No. 3 reactor’s storage pool. Fire engines spray water from the ground.
March 20 — Reactors 5 and 6 achieve cold shutdown.
April 2 — Highly radioactive water is confirmed flowing into the sea from reactor 2.
April 12 — The government raises the crisis severity level to 7, the highest on the international scale, bringing it on par with the 1986 Chernobyl disaster.
April 17 — The government and Tokyo Electric Power Co. announce a two-phase road map to bring the crisis under control.
April 22 — The government designates a 20-km radius around the plant as a no-go zone, while setting a ring 20 km to 30 km from the plant as an area that will have to be evacuated if further emergencies develop. In addition, evacuation is advised but not mandatory for an area beginning at the 20-km line and stretching beyond 30 km.
June 7 — The government admits meltdowns occurred in the cores of reactors 1, 2 and 3.
June 27 — Tepco starts cooling the damaged reactors using water decontaminated through a newly installed water treatment system.
July 19 — The government and Tepco say “Step 1” of the road map is largely completed and revise the conditions for completing the second phase and containing the crisis.
Sept. 8 — New Prime Minister Yoshihiko Noda visits the crippled plant for the first time.
Sept. 19 — Nuclear disaster minister Goshi Hosono announces a plan at a meeting of the International Atomic Energy Agency to move the deadline for cold shutdown forward to the yearend instead of mid-January.
Sept. 28 — Temperatures at the bottom of the pressure vessels for reactors 1, 2 and 3 fall below 100 degrees.
Sept. 30 — The evacuation preparation zones are lifted.
Nov. 4 — The government decides to provide Tepco with ¥891 billion to help pay its massive compensation bills.
Dec. 2 — Tepco unveils an interim report on an in-house investigation blaming the accident on a tsunami of unprecedented scope, though other disclosures show it was warned in advance.
Dec. 16 — The government declares the remaining reactors are in cold shutdown, completing the road map’s second phase.
Dec. 21 — The government and Tepco announce a plan to scrap reactors 1 through 4 in the next 30 to 40 years.
Dec. 26 — The government decides to reclassify the Fukushima evacuation zones into three categories, depending on radiation levels. The government’s accident investigation panel says in an interim report that the government and Tepco responded poorly to the crisis.
Jan. 26 — The government announces a plan to complete decontamination work in some evacuation areas by March 2014.
Feb. 13 — The government decides to offer Tepco an additional ¥689.4 billion for compensation payments.
Feb. 28 — A private-sector panel says Kan’s response to the crisis created unnecessary confusion. He made sure Tepco’s staff didn’t flee.