![]() ![]() When radiation is at the 400-millisievert-an-hour level, the nuclear plant workers are at risk of radiation sickness, depending on the length of exposure.įor example, a total dose of a thousand millisieverts in a day-say from two brief exposures to 500 millisieverts-can cause temporary radiation sickness, leading to nausea and decreased blood count but not death.Ī few minutes of 5,000 millisieverts would likely kill about half those receiving it within a month, unless aggressive medical intervention was provided. ![]() People get radiation sickness-technically known as acute radiation syndrome-when they receive high doses of radiation over the course of minutes or hours. (Related: 20 "unforgettable" pictures of the Japan tsunami and its aftermath.) "You saw radiation levels around the plant shoot up, although those appeared to have dropped off" soon afterward, added Higley, head of nuclear engineering and radiation health physics at Oregon State University.Īt times on Tuesday, exposure levels at the nuclear plant reached up to 400 millisieverts of radiation an hour before plunging to 0.6 millisievert an hour, according to the International Atomic Energy Agency (IAEA).Ī millisievert is the internationally accepted measure of radiation dose based on biological effects in humans, according to the IAEA.įour hundred millisieverts an hour is "a lot-you certainly don't wish to be hanging around there for any period of time," Higley said.īy contrast, the average person receives about one to two millisieverts a year from natural sources in their environments, and one chest x-ray yields about 0.2 millisievert.įifty millisieverts is the lowest cumulative annual dose for which there is evidence of radiation-related cancer in adults, according to the World Nuclear Association. On Tuesday, for example, an apparent crack in one of the nuclear plant's four compromised reactors likely resulted in "a puff release, perhaps of radioactive steam," said health physicist Kathryn Higley. The Fukushima Daiichi crisis is so tense in part because of its unpredictable, seesawing radiation levels. (See "Japan Battles to Avert Nuclear Power Plant Disaster.") What level of radiation exposure are the Fukushima workers-and everyday people-facing? Is the situation worse than Three Mile Island-or Chernobyl? ![]() As an emergency crew attempts to prevent a catastrophic meltdown at Japan's Fukushima Daiichi nuclear power plant, dangerous radiation levels have prompted local evacuations and trepidation across the country, which is already reeling from the massive March 11 earthquake and tsunami. ![]()
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