An autoradiograph image of a radioactive cesium microparticle, which shows the relatively high levels of radioactivity contained in the particle. Credit: Dr. Satoshi Utsunomiya
March 11, 2019
The microscopic particles unleashed by the plant’s explosions are also a potential environmental and health concern
On March 14 and 15, 2011, explosions unleashed invisible radioactive plumes from the Fukushima Daiichi Nuclear Power Plant, crippled three days earlier when the strongest recorded earthquake in Japan’s history triggered a massive tsunami. As the plumes drifted over the neighboring countryside, their contents—including radioactive cesium, a by-product of the plant’s fission reactions—fell to the ground and over the ocean.
What no one knew or expected was the fallout also contained bacteria-size glassy beads, with concentrations of radioactive cesium that were far higher than those in similar-size motes of tainted dust or dirt.
Since these particles were discovered in 2013, scientists have plucked them from soil samples and air filters throughout the contamination zone, including filters as far away as Tokyo. The beads could pose an under-recognized heath risk, researchers say, because they are tiny enough to be inhaled deep into the lungs—and their glassy makeup means they may not easily dissolve or erode. They also present an opportunity to conduct what one researcher called “nuclear forensics”: By analyzing the particles’ composition, scientists can piece together a clearer image of what happened during the white-hot violence inside the plant itself, and of the current condition of the debris in the three reactors that experienced meltdowns. This could help inform the strategy for cleaning up the ruins of the plant.
Researchers say a picture of the unusual beads is coming into focus against a backdrop of the Japanese public’s general nuclear wariness, and the government’s desire to put the Fukushima incident behind it—particularly with Tokyo poised to host the 2020 Olympics. “I think, unfortunately, the reaction to this discovery [of the beads] has been not very welcomed in Japan,” says Rod Ewing, a mineralogist and nuclear materials expert who co-directs the Center for International Security and Cooperation at Stanford University.
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