Radioactive Chemicals in California Tracked to Fukushima Meltdown
Radioactive sulphur signal adds to evidence of catastrophe.
Radioactive Chemicals in California Tracked to Fukushima Meltdown
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By Geoff Brumfiel of Nature magazine
Scientists in California are reporting raised levels of radioactive chemicals in the atmosphere in the weeks following the disaster at Japan's Fukushima Daiichi nuclear power plant. The measurements are the latest evidence that the reactors melted down catastrophically.
Researchers at the University of California, San Diego (UCSD), say that radioactive sulfur from the stricken power plant reached California in late March, two weeks after the crisis at Fukushima began. The sulfur is a by-product of emergency procedures taken immediately after the accident. The work is published in the Proceedings of the National Academy of Sciences.
On 11 March, the Fukushima Daiichi plant was shaken by a magnitude-9 earthquake and slammed with a 13-metre-high tsunami. The disaster knocked out emergency generators designed to back up systems that cooled the plant's three operating reactors.
In a desperate attempt to slow heating and avert a total meltdown, operators flooded the reactor cores with boric acid and sea water. But it didn't work: in May, the Tokyo Electric Power Company, which oversees the plant, announced that despite their best efforts, the reactors at Fukushima Daiichi had melted down completely.
Chemical corroboration
The latest measurements seem to confirm that. For several years, Mark Thiemens, a chemist at UCSD, and his group have been measuring atmospheric levels of a radioactive isotope of sulfur, 35S, which is usually generated by cosmic rays striking argon atoms in the atmosphere. On 28 March, the team detected levels of radioactive sulfur dioxide gas (35SO2) and sulphate aerosols (35SO4-2) that were well above the natural background.
The chemicals posed "no risk" to residents in San Diego, says Thiemens. In fact, it took a year to even develop equipment sensitive enough to measure levels as low as these, he says.
Thiemens and his colleagues believe that the radioactive sulfur was produced from chlorine in the sea water used to flood the reactors. The chlorine atoms probably absorbed neutrons from the ruined nuclear fuel, and were transmuted into 35S. They then escaped the reactor in both gas and aerosol form and were spread across the ocean by strong westerly winds.
Although 400 billion may sound like a lot, it's tiny in comparison with the normal flux of neutrons inside a reactor, says Patrick Regan, a nuclear physicist at the University of Surrey in Guildford, UK. Regan says that the neutrons do not indicate that the melted reactors restarted after the emergency began, but are a clear by-product of sea water inside the reactors.On the basis of models, the team estimates that around 400 billion neutrons per square metre 'leaked' from the reactor cores at the time of the meltdowns.
Thiemens says that the most significant contribution of the measurement may be in helping researchers to better understand how sulphates and other aerosols travel through the atmosphere after a nuclear accident. Fukushima provided a single, well defined source of traceable radiation, he says. Follow-up studies with Japanese colleagues "will be very significant in uniquely addressing how, and how fast, radioactivity spreads".
This article is reproduced with permission from the magazine Nature. The article was first published on August 15, 2011.
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17 Comments
Add CommentSlow news day, eh?
Reply | Report Abuse | Link to thisAnother nail in the tomb of the nuclear power industry, eh?
Reply | Report Abuse | Link to this"Another nail in the tomb of the nuclear power industry, eh?"
Reply | Report Abuse | Link to this-Read the article stupid person. The levels are negligable as stated. We have extremely sensitive instruments at this stage of our developement, therefore a detection does not indicate a danger. If you were to compare the cancer caused by this minute amount of radiation to the cancer caused by the pollution around San Diego, on of the most polluted cities on the planet, there would be no comoparison. The air pollution kills far more people, far more by multiple orders of magnitude. Therefore, shouldn't you be pointing the figure at fossil fuels and not nuclear? If not, explain your logic please.
Well, whatever your evidence, you have to admit that the Fukushima disaster has been the worst PR incident for the nuclear industry since Chernobyl. People are rethinking whether they want new reactors to be built or whether they want the old ones to continue operating or not. Regulators are realizing how natural disasters can affect reactors and are adjusting their safety requirements (somewhat) accordingly. These new safety requirements are adding to the already extremely high cost of reactor construction. Already, reactors in San Antonio, TX and Ontario Canada have had such huge cost overruns that the utilities financing the construction have walked away from the deal.
Reply | Report Abuse | Link to thisThe fact that we're seeing meltdowns every 20 years (or 1 reactor meltdown per decade on average) isn't the issue. The damage to health and property that Chernobyl, Fukushima or any future disaster isn't really the issue either. Those disasters are bad enough, but designing a reactor that can prevent future Fukushima-style incidents looks to be way too expensive, will take way too long to build and present too high a probability of cost overruns for any utility to handle. The DoE forecasted a 50% default rate for their Nuclear Power Loan Guarantee program. Defaulting or cancelling a single(!) reactor has caused economic hardship for utilities and ratepayers in the past. Many utilities had to go bankrupt or go through painful reorganization. Now that reactors will be even more expensive to build in the wake of Fukushima, the future for nuclear power looks even worse.
Commenting on this issue would be redundant after reading the prior comments so I opt to ask these distinguished commenter’s a question(s). What is the effect of this atmospheric damage on the time table science has given our dying earth? and : San Diego and LA air pollution, why don't I see articles on health threats & clean-up tactic's etc...?
Reply | Report Abuse | Link to thisCommenting on this issue would be redundant after reading the prior comments so I opt to ask these distinguished commenter’s a question(s). What is the effect of this atmospheric damage on the time table science has given our dying earth? and : San Diego and LA air pollution, why don't I see articles on health threats & clean-up tactic's etc...?
Reply | Report Abuse | Link to thisCommenting on this issue would be redundant after reading the prior comments so I opt to ask these distinguished commenter’s a question(s). What is the effect of this atmospheric damage on the time table science has given our dying earth? and : San Diego and LA air pollution, why don't I see articles on health threats & clean-up tactic's etc...?
Reply | Report Abuse | Link to thisTurn on the news once in awhile. You will get the smog alert for LA/San Diego every day. There are no immediate cleanup tactics, because there is nothing practical that can be done about it. People have grown to accept it.
Reply | Report Abuse | Link to thisThe same goes for radiation. We are exposed to it everyday. There is nothing you can do about that except stop living. Even when you die your body gives off radiation! People need to stop being sheep and look at the facts. The facts of this article, "The chemicals posed "no risk" Everything else is just filler.
Oh my goodness. The absorption of a neutron by Cl35 produces Cl36, not S35. The only way to get S35 from Cl34 (76%abundance) is..well you can't. If you start with Cl37 (24%abundance) you would need to knock a deuterium particle out to produce S35. If you start with Cl34 and absorb a neutron it produces Cl35 with a 10^5 year half-life. oh my goodness.
Reply | Report Abuse | Link to thisThe element sulfur is comprised of four stable isotopes, one of which is S34 (4% abundance). The cross-section for thermal neutron absorption of S34 is marginal, but if we ignore that, it is possible to produce S35 by neutron activation of S34. Please think this stuff out before you put it in print.
Reply | Report Abuse | Link to thisdrmarton: The chemistry is great and impressive but it doesn’t answer my questions: What I want to know is how these catastrophes effect global warming and the current perceived time table we have to reverse these problems and replenish the earth to a healthy state?
Reply | Report Abuse | Link to thisUnder neutron bombardment, 35Cl is transmuted to 35S via an (n, p) reaction. Look it up. The latter isotope has an 87-day half-life, making it both long-lived enough and radioactive enough to measure in the miniscule amounts detected.
Reply | Report Abuse | Link to thisdrmorton20: The chemistry is all well and good but doesn't answer my question. Perhasp no one really knows as yet how this castastrophe will effect our earths current eco systems rate of decline?
Reply | Report Abuse | Link to thisH Edward: I did try to look it up and what I have surmised is that science doesn't know yet what the actual outcome will be, and I couldn't find anyone willing to give me an educated guess either?
Reply | Report Abuse | Link to thisLoriG -- I was trying to dispel drmortin20's doubt as to the nucleons involved. That's physics. As to the chemical effect of the sulfur -- the amounts they detected are so tiny -- a handful of atoms, more or less --that there essentially are no effects. Outside of the immediate area (well, if several thousand square miles can be called "immediate area") the ecological damage is likely to be small compared to the other things we're doing to Earth's ecosystem.
Reply | Report Abuse | Link to thisDear LoriG,
Reply | Report Abuse | Link to thisThe effect of the rapidly increasing human population on the Planet , now over 7 Billion and heading rapidly towards 8 Billion, will be much,much more devastating that the Fukashima plant problem
If you care to check on the IAEA website and do more checking you will find that not one , repeat not one person has died or has even received radiation over that of internationally accepted safe limit of exposure.
The hysteria generating mis-information generated by the mass media is going to kill a lot of people .
PS - Have a look at the back page of September edition of Scientific American , and you will find some reliable information about what kills thousands of Americans every year.
This article is interesting in that demonstrates the ability of radioacive particles to disperse, and illuminates the patterns of dispersal. This should not be taken as evidence that uncontrolled release of radiation to the environment is 'safe' or not cause for concern. In the US, Fukushima should be less of a concern than the radioactive plume of contaminated groundwater making its way to the Columbia river.
Reply | Report Abuse | Link to thisStill, good to see the pro nuke loby well represented online.