Informative Research on the 2011 Fukushima Daiichi Disaster
The Fukushima Daiichi accident began on 11 March 2011 and lasted three days. Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident. The Great East Japan Earthquake of a magnitude 9.0 did considerable damage. The large tsunami created from this caused even more. The earthquake was centred 130km offshore the city of Sendai in Miyagi prefecture on the eastern coast of Honshu Island (the main part of Japan). It was a rare and complex double quake giving a severe duration of about 3 minutes. An area of the seafloor extending 650 km north-south moved typically 10-20 metres horizontally. Japan moved a few metres east and the local coastline subsided half a metre. The tsunami inundated about 560km² and resulted in a human death toll of at least 20,000, and much damage to coastal ports and towns, with over a million buildings destroyed or partly collapsed.
The tsunami waves that were generated by the main shock of the Japan earthquake (March 11,2011), damaged the backup generators at the Fukushima Daiichi plant. Although all three of the reactors that were operating were successfully shut down, the loss of power caused cooling systems to fail in each of them within the first few days of the disaster. Rising residual heat within each reactor’s core caused the fuel rods in reactors 1, 2 and 3 to overheat and partially melt down, leading to the release of radiation. Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and burnt sizeable holes in the floor of each vessel. These holes partially exposed the nuclear material in the cores. Explosions resulting from the build-up of pressurized hydrogen gas occurred in the outer containment buildings enclosing reactors 1 and 3 on March 12 and March 14. Workers attempted to cool and stabilize the three cores by pumping seawater and boric acid into them. Because of the concerns over possible radiation exposure at the time, government officials established a 30km no fly zone around the facility, and a land area of 20km radius around the plant, which covered nearly 600 square km that was evacuated.
A third explosion occurred on March 15 in the building surrounding reactor 2. At the time the explosion was thought to have damaged the containment vessel housing the fuel rods. In actuality, the explosion punched a second hole in the containment vessel, the first hole had been created earlier by melted nuclear that passed through the bottom of the vessel. In response, government officials designated a wider zone, extending to a radius of 30km around the plant, within which residents were asked to remain indoors. The explosion, along with a fire touched off by rising temperatures in spent fuel rods stored in reactor 4, led to the release of higher levels of radiation from the plant.
In the days that followed, 47,000 residents left their homes, many people in areas near to the 20km evacuation warning zone also prepared to leave. Workers at the plant made several attempts to cool the reactors using truck-mounted water cannons and water dropped from helicopters. Those efforts met with some success, which temporarily slowed the release od radiation, however, they were suspended several times after rising steam or smoke signalled an increased risk of radiation exposure. As workers continued their attempts of cooling down the reactors, the appearance of increased levels of radiation in some local food and water supplies, which caused the Japanese and international officials to issue warnings about their consumption.
At the end of March, the evacuation zone was expanded to 30km around the plant, and the ocean water near the plant was discovered to have been contaminated with high levels of iodine-131, which resulted from leakage of radioactive water through cracks in trenches and tunnels between the plant and the ocean. On April 6 plant officials announced that those cracks had been sealed, and later that month workers began to pump the irradiated water to an on-site storage building until it could be properly treated.
Months after the accident, radiation levels remained high in the evacuation zone, and government officials remarked that the area might be uninhabitable for decades. They also announced that radiation levels had declined enough in some towns located just beyond the original 20km evacuation warning zone that residents could return to their homes there. Beginning in July 2013, evacuation orders were lifted in some areas characterised by lower levels of radiation both within and beyond the 20km evacuation warning zone. By March 2017, all evacuation orders in the area outside the difficult to return zone had been lifted. A 2016 study on the effects of the accident on fish and marine products showed that the contamination level had decreased dramatically over time, though the radioactivity of some species, especially sedentary rockfish, remained elevated within the exclusion zone.
More on the Tsunami
The sudden horizontal and vertical thrusting of the Pacific Plate, which has been slowly advancing under the Eurasian Plate near Japan, displaced the water above and spawned a series of highly destructive tsunami waves. A wave measuring about 33 feet high inundated the coast and flooded parts of the city of Sendai, including its airport and the surrounding countryside. According to some reports, one wave penetrated roughly 6 miles inland after causing the Natori River, (which separates Sendai from the city of Natori to the south) to overflow. Damaging tsunami waves struck the coasts of Iwate prefecture, just north of Miyagi prefecture, and Fukushima, Ibaraki, and Chiba, the prefectures extending along the Pacific coast south of Miyagi. In addition to Sendai, other communities hard-hit by the tsunami included Kamaishi and Miyako in Iwate; Ishinomaki, Kesennuma, and Shiogama in Miyagi; and Kitaibaraki and Hitachinaka in Ibaraki.
The earthquake triggered tsunami warnings throughout the Pacific basin. The tsunami raced outward from the epicentre at speeds that approached about 500 miles (800 km) per hour. It generated waves 11 to 12 feet high along the coasts of Kauai and Hawaii, and 5-foot waves along the island of Shemya in the Aleutian Islands. Several hours later a 9-foot tsunami waves struck the coasts of California and Oregon in North America. Finally, about 18 hours after the quake, waves roughly 1 foot high reached the coast of Antarctica and caused a portion of the Sulzberger Ice Shelf to break off its outer edge.
Deaths (total) – 20,000 +
Deaths by the earthquake and tsunami– 19, 500
Evacuees – 47,000
Death from stress factors of evacuation – 2,202
Injured – 4,100.
Death from radiation exposure – 1 cancer death of a man who worked at the plant at the time of the accident was attributed to radiation exposure by a Japanese government panel.
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