![]() ![]() On April 12 nuclear regulators elevated the severity level of the nuclear emergency from 5 to 7-the highest level on the scale created by the International Atomic Energy Agency-placing it in the same category as the Chernobyl accident, which had occurred in the Soviet Union in 1986. 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. At the end of March, the evacuation zone was expanded to 30 km around the plant, and 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. Those efforts met with some success, which temporarily slowed the release of radiation however, they were suspended several times after rising steam or smoke signaled an increased risk of radiation exposure.Īs workers continued their attempts to cool the reactors, the appearance of increased levels of radiation in some local food and water supplies prompted Japanese and international officials to issue warnings about their consumption. In the days that followed, some 47,000 residents left their homes, many people in areas adjacent to the 20-km evacuation warning zone also prepared to leave, and workers at the plant made several attempts to cool the reactors using truck-mounted water cannons and water dropped from helicopters. Because of concerns over possible radiation exposure, government officials established a 30-km (18-mile) no-fly zone around the facility, and a land area of 20-km (12.5-mile) radius around the plant-which covered nearly 600 square km (approximately 232 square miles)-was evacuated. ![]() Workers sought to cool and stabilize the three cores by pumping seawater and boric acid into them. Explosions resulting from the buildup of pressurized hydrogen gas occurred in the outer containment buildings enclosing reactors 1 and 3 on March 12 and March 14, respectively. Those holes partially exposed the nuclear material in the cores. Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and bored sizable holes in the floor of each vessel-a fact that emerged in late May. 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 at times to the release of radiation. 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. TEPCO officials reported that tsunami waves generated by the main shock of the Japan earthquake on March 11, 2011, damaged the backup generators at the Fukushima Daiichi plant. At the time of the accident, only reactors 1–3 were operational, and reactor 4 served as temporary storage for spent fuel rods. The facility, operated by the Tokyo Electric and Power Company (TEPCO), was made up of six boiling-water reactors constructed between 19. The site is on Japan’s Pacific coast, in northeastern Fukushima prefecture about 100 km (60 miles) south of Sendai. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!įukushima accident, also called Fukushima nuclear accident or Fukushima Daiichi nuclear accident, accident in 2011 at the Fukushima Daiichi (“Number One”) plant in northern Japan, the second worst nuclear accident in the history of nuclear power generation.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives. ![]()
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