Until now, scientists and disaster experts thought cesium-137 fallout from the Fukushima reactor meltdown was in this soluble form. That guided their cleanup efforts, like removing and washing topsoil, and helped them map where radiation might spread.
It turns out that wasn’t entirely true. Satoshi Utsunomiya, a geochemist at Kyushu University in Japan, announced over the weekend that he had found cesium-137 in a new form: trapped inside tiny glass particles that spewed from the damaged reactors. These particles are not water soluble, meaning we know very little about how they behave in the environment—or in our bodies. He found the particles in air filters placed around Tokyo at the time of the disaster.
According to Utsunomiya, high temperatures inside the malfunctioning reactors at the Fukushima plant melted and broke down the concrete and metal in the buildings. Silica, zinc, iron, oxygen and cesium-137 fused into millimeter-wide glass microparticles, each about the size of a pin’s head. Lifted into the atmosphere by the fires raging at the plant, they then blew about 240 kilometers southwest to Tokyo.
“As much as 89% of all of the cesium [in Tokyo] was in fact in these particles. It’s profound,” says Daniel Kaplan, a geochemist at Savannah River National Laboratory in South Carolina. He attended Utsunomiya’s lecture describing the findings at the ongoing Goldschmidt Conference in Yokohama, Japan.
Kaplan says similar particles were observed near the Chernobyl reactors after the explosion there in 1986. But they were only seen within about 30 kilometers; beyond that, cesium-137 was only observed in rain.
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