Fukushima disaster summary

Japan is an island nation lying off the eastern coast of the Asian continent. The archipelago consists of four main islands Hokkaido, Honshu, Shikoku, and Kyushu, as well as thousands of adjacent smaller islands. Its total land area is 377,818 sq km, which is about 4% of that of the United States and slightly bigger than Germany. Japan occupies about 0.3% of the earth's total land area.

The country is situated in a volcanic zone along the Pacific deeps, which causes about 1,500 earth tremors every year and destructive earthquakes occur several times a century. Volcanic activity is occasional, due to the large number of dormant and active volcanoes. Because of close proximity to human populations they are being constantly monitored. Tsunamis and typhoons are also among the natural hazards.

Sounds like quite active place to live in, but what happens when two natural hazards occur simultaneously? A disaster of enormous magnitude resulting in numerous lost lives, hundreds of injured people and a nuclear peril for the entire region.

Fukushima nuclear powerplant was hit by tsunami
On March 11, 2011, an undersea 9.0 magnitude earthquake hit Japan. With the epicenter approximately 70 km east of the Oshika Peninsula of Tōhoku a tsunami following the earthquake had a devastating effect on the nearby coast. It was the most powerful known earthquake to have hit Japan, and one of the five most powerful earthquakes in the world overall since modern record-keeping began in 1900.

The massive tsunami crippled the cooling systems at the Tokyo Electric Power Company's (TEPCO) nuclear plant in Fukushima. It also led to hydrogen explosions and reactor meltdowns that forced evacuations of those living within a 20km radius of the plant.

The plant was designed to withstand an earthquake of 8.2 on the Richter scale but the earthquake was a 9.0, which in combination with tsunami proved fatal. Experts consider it to be the largest nuclear accident since the Chernobyl disaster, because more complex multiple reactors are involved. The entire plant was flooded, including low-lying generators and electrical switchgear in reactor basements and external pumps for supplying cooling seawater.

Nuclear reactor problems
The connection to the electrical grid was broken as the tsunami destroyed the power lines. All power for cooling was lost and reactors started to overheat, owing to natural decay of the fission products created before shutdown. The flooding and earthquake damage hindered external assistance.

In attempt to cool down the nuclear reactors and fuel cores TEPCO has been spraying water and sea water on the Fukushima plant. Their actions led to even greater problems, such as radiation being emitted into the air in steam and evaporated sea water. Another problem was generating hundreds of thousands of tons of highly radioactive sea water that has to be disposed of in the process of cooling down the reactors.

In the hours and days that followed, reactors 1, 2 and 3 experienced full meltdown. Hydrogen explosions destroyed the upper cladding of the buildings housing reactors 1, 3, and 4. An explosion damaged the containment of reactor 2 and multiple fires broke out at reactor 4. Current situation in the Fukushima plant is stable, with TEPCO and the Japanese government struggling to keep the reactors under control. However, the effects of the incident will probably be felt in Japan for decades.

Next: Fukushima disaster radiation effects