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UC San Diego researchers concluded that 400 billion neutrons were released per square meter surface of the cooling pools at Fukushima Daiichi

The 9.0-magnitude earthquake that shook Japan and crippled the reactor at Fukushima Daiichi nuclear plant back in March caused quite a bit of havoc with the release of radioactive water, contamination of crops and of course, the thousands of lives lost. At the same time, news networks like CNN and MSNBC sensationalized reports, causing unnecessary nuclear-related fear. U.S. senators even demanded the Nuclear Regulatory Commission to repeat an expensive inspection of U.S. nuclear plants.

In an attempt to clear some confusion and understand exactly how much radiation actually leaked from the damaged nuclear reactor at the Fukushima Daiichi nuclear plant in Japan on March 11, atmospheric chemists at the University of California, San Diego, have produced the first quantitative estimate of how much radiation actually leaked from the reactor.

Mark Thiemens, study leader and Dean of the Division of Physical Sciences at UC San Diego, along with post-doctoral researcher Antra Priyadarshi, and a team of researchers, observed the amount of radioactive sulfur in the air soon after the earthquake in Japan and was able to report a quantitative measurement of the amount of radiation leaked.

When fuel rods melt, products like neutrons leak from the fuel rods. Seawater is used to cool the hot reactors, and absorbs the leaked neutrons. These neutrons "collide" with chloride ions in the seawater, which results in the loss of a proton out of the nucleus of a chloride atom and turns the atom into a radioactive form of sulfur. Most of this vaporizes into steam when the saltwater comes into contact with the hot reactors, and to avoid explosions due to the collection of hydrogen, operators vent the steam into the atmosphere. Once in the air, the sulfur reacts with oxygen to create sulfur dioxide gas and eventually sulfate particles.

On the other side of the Pacific Ocean in La Jolla, California on March 28, 2011, Thiemens and his team noticed an "unprecedented spike" in radioactive sulfur in the air. They used a model, which was based on the NOAA's observations of atmospheric conditions, to determine the path the air took to get to California over the previous 10 days, and found that it had come from Fukushima Daiichi.

The next step was to calculate how much radiation had leaked from the reactor based on the path over the Pacific Ocean. They took into account that some sulfate particles had fallen into the ocean or decayed along the way, and concluded that 400 billion neutrons were released per square meter surface of the cooling pools. They predicted that this occurred between March 13, 2011 and March 20, 2011. March 13 was when operators began flooding the reactor with seawater.

"You know how much seawater they used, how far neutrons will penetrate into the seawater and the size of the chloride ion," said Priyadarshi. "From that, you can calculate how many neutrons must have reacted with chlorine to make radioactive sulfur."

To achieve the levels observed in California, the team said the concentrations a kilometer above the ocean close to Fukushima must have been 365 times above normal levels. Over the four days that the team took measurements, which ended March 28, Thiemens measured 1501 atoms of radioactive sulfur in sulfate particles per cubic meter of air. They mentioned that this was the highest they had seen in two years of observations and recordings.

According to the researchers, the radioactive sulfur observed was produced by partially melted nuclear fuel in the storage ponds or reactors. While cosmic rays can produce radioactive sulfur, the team noted that these rays rarely mix into the layer of air right above the ocean.

Despite the high levels of radioactive sulfur recorded in California, Thiemens and his team said these levels were not dangerous to human health.

"Although the spike that we measured was very high compared to background levels of radioactive sulfur, the absolute amount of radiation that reached California was small," said Thiemens. "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."

This study was published in Proceedings of the National Academy of Sciences.

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RE: Sensationalized?
By goodsyntax on 8/17/2011 10:08:33 AM , Rating: 2
You should get your facts straight before you spout off like this.

- Nuclear power has one of the lowest total death rates of any power generation method (Reference:

- Radiation comes in numerous forms, some, such as Alpha radiation can't even penetrate a sheet of paper. Others are only dangerous if ingested.

- There is a branch of healthcare (Nuclear Medicine) which utilizes and introduces radiation into the human body for the treatment, imaging and diagnosis of numerous ailments. This is certainly not dangerous, and much to the contrary has saved countless lives.

- Radiation occurs naturally and is everywhere, from cosmic rays, to natural sources like C-14 (which is used in radio-carbon dating), K-40 (or potassium, which is found in many foods), Radon Gas (another naturally occurring source). In fact, a nuclear fission reaction occurred naturally in Oklo, Gabon, Africa 1.5 billion years ago - long before men and their evil nuclear reactors.

- Coal based power plants release more radioactivity into the atmosphere than nuclear power plants, especially older ones that do not have an effective fly ash recapture program.

- Fly ash (a byproduct of coal based power plants) is a major contributor of background radiation exposure to humans and is currently a major source material for sheet rock production.

Finally, how do you propose generating over 84,000 MegaWatts per day to replace the capacity generated at all US nuclear power plants?

- Are you willing to dedicate an area of 300 square miles to wind turbines for each nuclear reactor site you want to replace?

- Maybe you are willing to sacrifice 200 square miles to solar farms for each nuclear reactor site?

The fact is that the energy density in a nuclear powerplant is unrivaled. A nuclear site encompassing about 7 square miles produces the same energy output as hundreds of square miles of alternative energy sources. Add in the fact that high voltage transmission infrastructure is already in place at these sites and the alternatives do not, makes the decommissioning all nuclear powerplants an expensive proposition monetarily and ecologically as well.

Finally, I'm not sure where you get your facts regarding death rates due to Nuclear power. The fact is that the safety records at nuclear powerplants are unrivaled, even given Chernobyl and Fukushima. Consider for a moment that not a single nuclear powerplant worker has died in any of the 104 nuclear sites, spread over 40 years of service. More people have died from dog bites this year alone than in the entire history of US nuclear power.

Just some food for thought...

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