Magazine article Science News

Japan Nuke Accident Seen in Seattle: Clues to Events at Crippled Plant Found in Traces of Radiation

Magazine article Science News

Japan Nuke Accident Seen in Seattle: Clues to Events at Crippled Plant Found in Traces of Radiation

Article excerpt

Radioactive particles wafting from Japan to Seattle have been used as a window on recent events inside the crippled Fukushima Daiichi nuclear power plant. Working backward from trace nuclear by-products, physicists have confirmed that contaminated steam is the source of this radiation, not spent fuel rods or material ejected into the atmosphere directly from the reactor core.

"We haven't seen any of the heavier stuff that would come right from the core, which people saw 30 years ago during the Chernobyl accident," says Andreas Knecht, a nuclear and particle physicist at the University of Washington in Seattle who, along with colleagues, published the new data online March 24 at arXiv.org.

Starting March 16, Knecht's team saved and analyzed filters that clean 100 million liters of air every day in the ventilation system of the University of Washington's physics and astronomy building. With a detector originally designed to spot neutrinos coming from outer space, the researchers searched for gamma rays originating in the by-products of nuclear fission. The first such by-products from Japan were detected on March 18.

The mix of elements found in the filters drives home the differences between the Chernobyl and Fukushima disasters. The total meltdown of the Chernobyl reactor in 1986, which exposed the core, belched tons of radioactive material from fuel rods directly into the atmosphere. At the time, scientists in Paris detected 20 different isotopes. The partial meltdown of Fukushima, in contrast, released only five isotopes measurable by the Seattle team: iodine-131, iodine-132, tellurium-132, cesium-134 and cesium-137. …

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