Fukushima Nuclear Facility: What Happened

Here's some data on what happened at each of the six nuclear reactors at Fukushima Dai-ichi (Big One) plant, and at four of the reactors at Fukushima Dai-ni (Big Two) plant.
After the pumping of seawater to cool the nuclear rods (active and spent), check out THIS blog entry posted earlier today.
For more data on the inner mechanisms of a nuclear plant, read THIS entry.

Fukushima No. 1 plant

• Reactor No. 1

1. Power operation suspended after earthquake;
2. Cooling failure due to lack of electricity to power cooling generators;
3. Partial meltdown of nuclear core;
4. Radioactive vapour vented;
5. Building containing the reactor is damaged by hydrogen explosion;
6. Seawater is pumped in to cool reactor cores to avoid explosion/meltdown.

• Reactor No. 2

1. Power operation suspended after earthquake; 
2. Cooling failure due to lack of electricity to power cooling generators;
3. Seawater pumped in to try and cool already exposed nuclear fuel rods;
4. Partial meltdown of fuels rods and thus core;
5. Radioactive vapour vented; 
6. Building containing the reactor damaged by an blast at Reactor No. 3;
7. Damage to containment vessel surrounding nuclear reactor core feared;
8. Potential meltdown feared;
9. Containment vessel may have a crack leaking out radioactive water and other contaminants.

• Reactor No. 3 

1. Power operation suspended after earthquake
2. Cooling failure due to lack of electricity to power cooling generators;
3. Radioactive vapour vented;
4. Seawater pumped in to try and cool already exposed nuclear fuel rods;
5. Building containing the reactor damaged by hydrogen explosion;
6. High-levels of radiation measured nearby
7. Smoke arising from reactor  - perhaps from spent-fuel storage pool;
8. Severe damage to containment vessel seems unlikely
9. Seawater dumped over pool by helicopter and water sprayed from ground.

• Reactor No. 4

1. Under maintenance when earthquake struck;
2. Fire within facility may have been caused by hydrogen explosion at a pool holding spent fuel rods;
3. Very high temperatures rise in spent-fuel storage pool;
4. Fire within the the building housing the reactor;
5. Cooling pool water level may be receding;
6. Renewed nuclear chain reaction feared.

• Reactors No. 5 & 6

1. Under maintenance when earthquake struck;
2. Cooling water temperatures in spent-fuel storage pools increased to about 64 C; 

•   Spent-fuel storage pools at all reactors

1. Cooling functions lost;
2. Cooling water temperatures or levels unobservable at reactors No. 1 to 4.

Fukushima No. 2 plant

• Reactors No. 1, 2, & 4

1. Power operation suspended after earthquake;
2. Cooling generator failure within reactors;
3. Cold shutdown initiated.

• Reactor No. 3

1. Operation suspended after quake;
2. Cold shutdown initiated.

Andrew Joseph