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http://news.sciencemag.org/sciencenow/2011/08/fukushima-reactor-damage-picked-.html?ref=em&elq=4923d143721040cea1de0b92f74deea1

 Fukushima Reactor Damage Picked Up in California Winds
by Daniel Strain<http://news.sciencemag.org/sciencenow/author/daniel-strain/index.html>
 on 15 August 2011, 4:23 PM | 1
Comments<http://news.sciencemag.org/sciencenow/2011/08/fukushima-reactor-damage-picked-.html#sci-comments>

ENLARGE IMAGE<http://news.sciencemag.org/sciencenow/assets/2011/08/15/sn-fukushima.jpg>
[image: sn-fukushima.jpg]<http://news.sciencemag.org/sciencenow/assets_c/2011/08/sn-fukushima-thumb-autox600-10781.jpg>
*Dousing Fukushima's reactors.* Air laden with radioactive material that was
formed after emergency teams soaked cores at an imperiled nuclear power
plant in Japan (shown) blew into San Diego, California, about 2 weeks later.
 Credit: Self Defence Force Nuclear Biological Chemical Weapon Defense
Unit/Reuters TV

On 28 March, scientists got a whiff of something strange in the air off a
pier in San Diego, California. The atmosphere had suddenly become flush with
radioactive sulfur atoms. That sulfur, it turns out, had traveled across the
Pacific from a nuclear power plant in Fukushima, Japan, that was shaken by
the 11 March earthquake and the
tsunami<http://news.sciencemag.org/cgi-bin/mt/mt-search.cgi?blog_id=8&tag=Japan%20Quake%202011&limit=20&IncludeBlogs=8>
and
aftershocks that followed. Now the same team has studied those radioactive
winds to come up with the first estimate of damage to the plant's cores at
the height of the disaster.

To cool fuel rods and spent fuel while stanching a total meltdown,
responders pumped several hundred tons of seawater into three reactors at
the Fukushima Dai-ichi nuclear power plant. The white-hot rods fizzled off
steam, which had to go somewhere. So workers vented it into the air.

Meanwhile, across the Pacific, atmospheric scientist Antra Priyadarshi of
the University of California, San Diego (UCSD), remembered a study she had
read a while back: Following underwater nuclear bomb tests in the 1950s and
'60s, physicists noticed that a heavy form of sulfur—sulfur-35—had
mushroomed. Nuclear reactions spit out lots of fast and therefore "hot"
particles called neutrons, which can then bang into abundant chloride ions
in saltwater, converting them to sulfur-35. Priyadarshi and her colleagues
were already tracking tiny traces of radioactive sulfur to study how layers
of air mix in the atmosphere, so all they had to do was wait.

They didn't have to wait long. The sulfur was already swirling over
Fukushima, where it had combined with oxygen to form sulfur dioxide gases
and fine particles of sulfates called aerosols. Soon, strong winds pushed
them east. Sulfur-35 does occur naturally—cosmic rays zap argon atoms in the
upper atmosphere, or stratosphere, to make radioactive sulfur. But little of
it makes its way down to the lowest slice of atmosphere, called the marine
boundary layer. On a normal day, Priyadarshi sees between 180 and 475
sulfur-35 atoms as sulfates per cubic meter of air, but on the 28th, her
team recorded about 1500. "No one has ever seen such a high percentage of
the stratospheric air coming into the marine-bound layer," she says.

The UCSD team ran a computer simulation to trace the path of the gases and
aerosols from Fukushima to the West Coast. Most sulfur-35 atoms likely
dispersed or rained down into the sea before hitting San Diego, but
Priyadarshi estimates that about 0.7% completed the trip, too few to become
harmful. Based on the simulation, about 365 times the normal levels of
radioactive sulfates had gathered over Fukushima during the
disaster<http://www.pnas.org/cgi/doi/10.1073/pnas.1109449108>,
Priyadarshi and colleagues report online today in the *Proceedings of the
National Academy of Sciences *(*PNAS*).

And because the researchers knew how many neutrons it would take to make
that much sulfur, they could estimate how many were expelled during the
disaster: For each square meter of reactor space doused by saltwater, the
nuclear material ejected 400 billion neutrons before 20 March. And that, in
turn, may give scientists a good look at the damage done to the cores during
the disaster, says study co-author Mark Thiemens, an atmospheric scientist
who is also at UCSD. If unchecked, these particles can heat up fuel rods and
stores of spent fuel to the point of causing disastrous meltdowns like the
one that rocked Chernobyl in 1986.

But Andreas Stohl, a scientist at the Norwegian Institute for Air Research
in Kjeller, isn't convinced. Trying to figure out what happened to
Fukushima's sulfur-35 as it was buffeted by haphazard winds on its nearly
10,000 kilometer journey to San Diego requires a lot of guesswork, he says:
"The uncertainties must be huge."

Karl Turekian, an atmospheric geochemist at Yale University who edited
Priyadarshi's paper for *PNAS*, agrees. But he adds the San Diego
researchers did their best to account for that atmospheric chaos. And
scientists haven't yet come up with any other way to estimate neutron
"leaks" from nuclear fuel. "Somebody didn't have a neutron thermometer in
Fukushima," he says.

Now that Fukushima's reactors have cooled back down, the biggest challenge
facing scientists will be to contain radioactive elements that escaped
during the disaster. Thiemens will be working with Japanese researchers to
follow sulfur-35's path through soil and streams near Fukushima to find
where even more harmful elements may have hidden.

*Correction:** A previous version of this article stated that winds pushed
sulfur over Fukushima west. It has been corrected to say east.*
-- 
******************************************
Michael Balter
Contributing Correspondent, Science
Adjunct Professor of Journalism,
New York University

Email:  [log in to unmask]
Web:    michaelbalter.com
NYU:    journalism.nyu.edu/faculty/michael-balter/
******************************************

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