What sulfur particles in California can tell us about Fukushima

During the early weeks of the Japan 3/11 crisis, after a tsunami critically damaged the Fukushima Daiichi nuclear power plant, we talked on Boing Boing about why Americans on the West Coast didn't need to worry about exposure to radioactive fallout. Shorter version: The levels of radiation that made it across the Pacific were far too low to cause a serious health concern.

Now here's something really interesting: The levels of fallout that made it across, while too low to pose a risk to humans, were detectable by extremely sensitive scientific equipment. And those measurements are now being used to document what happened at the site of the disaster.

In the process of trying to cool down the overheating reactors, officials in Japan dumped sea water and reaction-slowing boric acid into the reactor cores. The resulting chemical reaction—chloride ions in salt water combining with fast-moving neutrons from the reactor—produced a form of radioactive sulfur. Meanwhile, scientists at the University of California, San Diego, were already measuring sulfur particles in the air as part of climate research. Days after the crisis began, their instruments picked up the radioactive sulfur that had crossed the ocean.

Now, using modeling and some basic knowledge about how particles behave, they've been able to use the information they gathered in California to estimate how high radiation levels were in Fukushima in the early days of the crisis. A couple of things they've found: Further evidence that at least one of the reactor cores suffered a meltdown, and evidence suggesting that the damaged reactors didn't re-start after the emergency began—a possibility that has been pointed out by other scientists. I'll have a more in-depth look at this study later this week. For now, check out the write ups at Nature News and USA Today.

The full research paper is at The Proceedings of the National Academy of Sciences.

(Thanks, Miles O'Brien + Jenny Marder of PBS NewsHour)

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