| Date of accident |
11 March 2011 |
26 April 1986 |
| Accident details |
A magnitude-9.0 earthquake and resulting tsunami damaged the
plant's power systems, causing cooling systems to fail. A series of gas
explosions followed |
A sudden power output surge during a systems test caused a
reactor vessel to rupture, leading to a series of blasts. An intense
fire burned for 10 days |
| Severity rating |
Level 7 - major accident |
Level 7 - major accident |
| Number of reactors |
Six; but only three of concern, plus pools storing spent fuel |
Four; but only one reactor involved |
| Type of reactors |
Boiling-water reactors. Japanese authorities stress that
unlike at Chernobyl, the containment vessels at Fukushima remain intact.
Also, unlike Chernobyl, the reactors at Fukushima do not have a
combustible graphite core |
Graphite-moderated boiling water reactor. The graphite made
it highly combustible. The reactor also had no containment structure and
nothing stopped the trajectory of radioactive materials into the air |
| Radiation released |
370,000 terabecquerels* (as of 12 April) |
5.2 million terabecquerels* |
| Area affected |
Officials say areas extending more than 60km (36 miles) to
the north-west of the plant and about 40km to the south-southwest have
seen radiation levels exceed annual limits |
Contamination of an area as far as 500 km (300 miles) from
the plant, according to the UN. But animals and plants were also
affected much further away |
| Evacuation zone |
20km; 20-30km voluntary zone. Five communities beyond the existing evacuation zone have also been evacuated |
30km |
| People evacuated |
Tens of thousands |
The authorities evacuated, in 1986, about 115,000 people
from areas surrounding the reactor and subsequently relocated, after
1986, about 220,000 people from Belarus, the Russian Federation and
Ukraine |
| Related deaths |
No deaths so far due to radiation |
A UN report places the total confirmed deaths from radiation
at 64 as of 2008. Disputes continue about how many will eventually die |
| Long-term health damage |
Not yet known, but risks to human health are thought to be low |
Among the residents of Belarus, the Russian Federation and
Ukraine, there had been up to the year 2005 more than 6,000 cases of
thyroid cancer reported in children and adolescents who were exposed at
the time of the accident, and more cases can be expected during the next
decades |
| Current status |
Officials say radiation leaks are continuing and could
eventually exceed those at Chernobyl. The priority is restoring adequate
coolant to the fuel ponds and the reactors themselves |
The damaged reactor is now encased in a concrete shell. A new containment structure is due to be |
