vent some of the steam (which contained a small amount of radioactive material) into the air. 05:50: Fresh water injection into reactor 1 is started. 06:50: Although unknown at the time, the core of reactor 1 has now completely melted and falls to the bottom of the reactor pressure vessel. 10:09: TEPCO confirms that a small amount of vapor has been released into the air to release pressure in reactor unit 1 at Fukushima I. 10:58: Pressure still remains too high inside reactor unit 2 at Fukushima I. In order to alleviate some of this pressure, a consensus is reached to vent radioactive vapor into the air. 14:00: Operators open the containment venting line of unit 1 and receive confirmation of steam release to the atmosphere at 14:30. 14:50: Fresh water injection into reactor 1 is halted. 15:30: Evacuation of residents within 3 km of Fukushima II and within 10 km of Fukushima I are underway. 15:36: There is a massive hydrogen explosion in the reactor building of unit 1. The primary containment is not damaged, but there is extensive damage to the secondary containment (the reactor building). Five workers are injured. 19:00: Seawater injection into reactor 1 is started. TEPCO orders Daiichi to cease seawater injection at 19:25, but Daiichi plant boss Masao Yoshida orders workers to continue with the seawater injection. 21:40: The evacuation zone around Fukushima I is extended to 20 km, while the evacuation zone around Fukushima II is extended to 10 km. To release pressure within reactor unit 1 at Fukushima I, steam is released out of the unit into the air. This steam contains water vapor, hydrogen, oxygen and some radioactive material. TEPCO engineers decided to directly inject seawater inside the pressure vessel of the reactors by means of the mobile trucks of the firemen. The pressure relief was also necessary to allow the firemen to inject seawater into the reactors vessels. Sunday, 13 March 02:42: The high pressure coolant injection system for reactor 3 stops and, shortly thereafter, the water level within the reactor starts falling. 05:10: Fukushima I Unit 1 is declared as an INES Level-4 "accident with local consequences" event. 07:00 (approximate): The water level in reactor 3 reaches the top of the fuel. 09:00: Core damage starts occurring in reactor 3. A partial meltdown was reported to be possible at unit 3. At 13:00 JST reactors 1 and 3 are