Japan's Latest Radiation Scare Was Caused by Nuclear Paint

Illustration for article titled Japan's Latest Radiation Scare Was Caused by Nuclear Paint

The elevated radiation levels discovered in Tokyo's Setagaya Ward have been confirmed—thankfully—as not having originated from the damaged Fukushima power plant. So what was causing the Geigers to jump? A stash of radium-226 under a home's floorboards.

The mystery, though, is how they got there.

Japan's Science Ministry discovered the cache Thursday which consisted of numerous bottles and vials containing a white, powdered substance believed to be radium. Some containers bore the label, Nihon Yako ("Luminous Japan")— radium-226 can be used as a luminous paint.


Radiation levels at the surface of the bottles measured 600 microsieverts per hour. The elderly owner of the home said she was unaware of the materials stored beneath her. She reportedly had lived in the home from 1953 until February of this year while receiving about 30 mSv of exposure annually. Radium, when inhaled or ingested, accumulates in the bones and for every 100 mSv of exposure, increases one's chances of dying from cancer by one half percent.

Authorities have removed the isotopes from the property and stored them at a radioactive isotope disposal agency for the duration of their 1,600-year half life. [Japan Times]

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Hopefully it's stored for longer than just one half life, as it would still be giving off 300 microsieverts per hour.

Also, the "For Reference" part is rather misleading. Fukishima was giving off 400 milli sieverts per hour, while this was giving off 600 microsieverts, or 0.6 milli sieverts. Further, the 400 mSv number is actually what was outside of the plant - near the surface of the plant, it was giving off more like 10 sieverts per hour (10000 mSv), which is more accurate compared to the level at the surface of the bottle. The 30 mSv annual exposure for the resident is probably more useful for comparison in general as it represents how much might actually make it to a person.