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Water levels in reactor 1 drop to top of fuel rods, reactor heating begins. -
Water level in reactor 1 drops, fully exposing fuel rods. Temp of rods reached 2800 c, melt down begins. -
Nuclear emergency declared, initially listed as a level 4 event. Later it would be upgraded to a level 7. -
46 ft tsunami hits Daiichi nuclear plant, overcoming the 19ft seawall. Eight minutes later a second wave hits.
Reactors 1,2 and 3 are flooded.
Diesel generators are damaged, power is lost in 1 and 2. and cooling systems offline except old steam powered cooling system not tested in 40 yrs.
3 still has battery back-up. -
Great East Japan Earthquake hits. Magnitude 9.0 earthquake lasting 3 minutes hits off the coast of mainland Japan. Reactors 1, 2 and 3 automatically shutdown power as designed. All 6 external back up power sources are damaged and offline. Diesel generators in turbine basements come online -
Reactor 3 main water-cooling system fails as backup battery power runs out. Steam cooling system comes online. -
Reactor 1 pressure venting begins, but due to poor design of ducting and lack of power, gases backflow to service floor at top of reactor. -
Seawater injection via firehoses begins to cool reactor 1. -
Hydrogen explosion occurred at top floor of reactor 1, blowing off the roof. -
Reactor 3 Steam cooling system fails, water levels dropped quickly. Core meltdown begins. -
Seawater injection cooling begins in reactor 3.
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During pressure venting of reactor 3, gases backflow to service floor at top of reactor.
Reactor 3 suffers explosion of service floor blowing roof and walls off, demolishing the top of the building. Debris was very radioactive. -
Seawater injection cooling begins in reactor 2.
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Reactor 2 core meltdown begins. -
Reactor 2 steam cooling system fails. Reactor water levels begin dropping rapidly. -
After having to manually vent reactor 2, suddenly pressure drops, making venting unnecessary. It was later was discovered that a leak had developed in the primary containment chamber, releasing radioactive material into the air. – most radioactive releases came from reactor 2. -
Reactor 4 suffers an explosion from hydrogen gas backflowing from reactor 3 into reactor 4 through shared ducts. Explosion damages both reactor 4 and the main structure of reactor 3. -
After the last explosion of reactor 4, no other major events occurred. The days, months and years that followed were focused on containment and clean up.