For the first time, the amount of radiation leaked from the Fukushima nuclear meltdown in March was measured by a team of researchers. And the results show that tiny amounts of radioactive sulfur reached California in the weeks following the meltdown.
The amount of radioactive sulfur that arrived on the wind in California between March 22 and April 1 was tiny, and in fact "almost nothing," according to Mark Thiemens, a professor of chemistry at the University of California, San Diego.
"It took me three years to figure out the chemistry, to be able to measure things that low," he said.
Thiemens and his team operate a device that uses sulfur to measure radioactivity in the environment and have been operating it since 2009, looking at climate patterns and emissions coming from Asia across the Pacific to the U.S.
Initially, Thiemens stressed that harmful radiation will not reach the West Coast.
"The tsunami came and we were measuring, but we didn't expect to see anything because reactors don't make sulfur," said Thiemens.
As the reactors in Fukushima started to heat up, however, sea water was used in order to cool down the reactors. This caused some of the chlorine atoms in the sea water to absorb neutrons from the reactor, turning them into a radioactive type of sulfur called Sulfur 35, which is usually generated by cosmic rays striking argon atoms in the atmosphere.
The sulfur then escaped the reactor in both gas and aerosol form, traveling across the ocean by strong westerly winds.
Around 400 billion neutrons per square meter was released from the reactor cores in the weeks following the meltdown, concluded the team.
While the amount of radioactive sulfur was higher than normal background levels, it remains harmless.
"The levels we recorded aren't a concern for human health. In fact, it took sensitive instruments, measuring radioactive decay for hours after lengthy collection of the particles to precisely measure the amount of radiation," said Thiemens.
The most significant contribution of the measurement is that it helps researchers to better understand how sulphates and other aerosols travel through the atmosphere after a nuclear accident, reports Nature News.
Fukushima disaster provided a single, well defined source of traceable radiation, said Thiemens.
Follow-up studies with Japanese colleagues "will be very significant in uniquely addressing how, and how fast, radioactivity spreads."
Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi nuclear power plant in Fukushima prefecture, Japan, was devastated by Tsunami waves in March, and has been spewing radiation in water, air and soil, threatening lives of many.