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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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By letmepicyou on 8/16/2011 3:07:17 PM , Rating: -1
If there's anything I'm tired of is government agencies (and any 'private' agency funded either by the government or any private company that has a vested interest, including various universities that take payola) telling us there is "no public health risk". Lets look at a few knowns.

1: We KNOW radiation exists naturally. However, this fact is not mutually exclusive to the following:

2: We KNOW there is NO SAFE AMOUNT of radiation exposure. If you could eliminate it completely, you'd be better off.

3: We KNOW that governments lie to us any chance they get, sometimes seemingly just for the fun of it.

So when are we going to stop ALLOWING these parrots to repeat the same "no public health concern" propaganda speak? Every time these ridiculous words should spring forth from some pundit's big yap, we should punch then square in their lips and DEMAND they tell us the real truth. Truth such as, what percentage of a cancer increase of various types will we expect with the increase in radiation from various sources, be they cesium, sulfur, iodine, plutonium, or any of the host of others. And where in the demographic will we most likely see the result of this new radiation in our environment? In children? In unborn infants? In the elderly?

It's time for LESS parrot-speak and MORE truth-speak.

By boobo on 8/16/2011 3:51:46 PM , Rating: 2
2: We KNOW there is NO SAFE AMOUNT of radiation exposure. If you could eliminate it completely, you'd be better off.

I thought that if we eliminated all radiation completely, we would instantly freeze to death... no?

By MrTeal on 8/16/2011 4:08:39 PM , Rating: 2
Well, not instantly.

By letmepicyou on 8/16/2011 4:10:01 PM , Rating: 1
When posting at a site called "dailytech", one could hope for a modicum of intelligence in the posts. To infer that no one here knows the difference between the infrared radiation from the sun which provides our planet with heat, and ionizing radiation from beta and gamma sources locally within our environment, is ludicrous. If this is some kind of "joke", it's a poor one.

By Master Kenobi on 8/16/2011 7:05:22 PM , Rating: 2
The average DailyTech poster would most likely know the difference and it goes without saying. However, there are plenty of exceptions to that rule. The internet is a strange and terrifying place filled with people that probably shouldn't be allowed to exist, let alone vote and drive. All those warnings about thing not to do with a product came from people doing exactly that and someone sued over it. Just think, since the late 90's and early 00's all of those people are now on the internet posting stuff on websites just like this one. Scary shit isnt it?

By Dr of crap on 8/17/2011 8:54:28 AM , Rating: 2
And the problem that you list is -

They Do vote,
and they DO drive,
and they DO expect things to be handed to them and not work for them. And our society just caters to these people and doesn't stand up to them, and tell them NO.

By FITCamaro on 8/16/2011 7:41:51 PM , Rating: 1
If you eliminated all radiation other than output from the sun, you wouldn't know.

Why? Because it doesn't affect you in small amounts. The skin absorbs most of it.

By Hieyeck on 8/19/2011 11:51:03 AM , Rating: 2
Go Google the radioactivity of coal ash, a byproduct of burning coal for power.

Also bananas. Do us all a favor and stay away from your grocery store and starve.

By sleepeeg3 on 8/16/2011 7:41:41 PM , Rating: 2
More truth speak...
"these levels were not dangerous to human health"
All you need to know.

By zozzlhandler on 8/16/2011 8:23:12 PM , Rating: 3
Its not what you don't know that gets you, its the things you do know that just aint so.

I would not be nearly so sure that no radiation is healthy. There is evidence that a small level of radiation is beneficial to health. This would certainly make sense from an evolutionary point of view, since we evolved in a medium that included radiation.

By nmrahde on 8/17/2011 8:43:45 PM , Rating: 2
Some radiation is not just healthy, it's damn near necessary.

Our skin uses UV radiation to manufacture Vitamin D. There's actually a bunch of recent studies claiming that kids aren't getting ENOUGH radiation as nobody goes outside anymore.

Granted in a higher dose it can and will kill you. However this is true for pretty much everything from water to a 57 Studebaker.

Interesting side note for those not in the know - did you know the human body is naturally radioactive itself? Most of this comes from Potassium-40 (if I recall correctly). Apparently Potassium sometimes breaks down into this radioactive isotope.

Fun science experiment - fill your suitcase with bananas (or better yet, Brazil nuts) the next time you fly. The amount of Potassium-40 contained in a whole suitcase full should be enough to set off the airport's radiation detectors... :D

By Schrag4 on 8/17/2011 9:47:40 AM , Rating: 1
2: We KNOW there is NO SAFE AMOUNT of radiation exposure. If you could eliminate it completely, you'd be better off.

I'm not sure exactly what you mean by this. Since we all know that you cannot avoid radiation exposure, you must acknowledge that there's a certain level of radiation exposure that you personally will accept for yourself, right? Would you not get a chest x-ray or a CT-scan if your doctor said you needed one? Should women not get mammograms, especially those in families prone to breast cancer?

And if radiation exposure due to this accident turns out to be lower doses than these other forms of radiation that we willingly expose ourselves to, can't you see how this is a non-issue?

Or are you really, truely saying that you'd rather die of some undiagnosed illness than get an x-ray or CT-scan?

By nmrahde on 8/17/2011 9:03:36 PM , Rating: 1
Here's some more truth speak for you...

1. We KNOW radiation exists naturally. In all of us. Mostly in the form of Potassium-40.

2. We KNOW that UV radiation is necessary for the production of Vitamin D. If you could eliminate it completely you'd be like any number of fat kids who don't go outside anymore and have a Vitamin D deficiency.

3. Okay I don't really have an argument against this one.

As for the types of cancer increase from various sources, from what I understand there's a bit too many variables to make a simple chart for that. If you are truly concerned, stock up on iodine tablets. Your body will readily absorb iodine (radioactive or not) up to a certain point. If you're fully stocked on non-radioactive iodine your body will excrete the rest.

Many other radioactive materials aren't readily used in bodily processes so you only have to work about the radioactive particles themselves. Here what matters is the energy of the particle.

If I recall correctly (and I could easily be wrong lol) the heavier the particle the less energy it typically has. In most cases heavy alpha particles won't have enough energy to pierce the skin. Beta and gamma radiation have the potential to be more harmful as they can penetrate deeper.

------------------------------------------------- ----------
Perhaps more useful information for you (and all of us), would have been if the study provided the data in the form of Sieverts.

Straight from Wiki:
The sievert (symbol: Sv) is the International System of Units (SI) SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to the physical aspects, whichgray. are characterised by the absorbed dose, measured in that would have been far more useful in determining if this amount of radiation was actually harmful. It also would have been far less sensational.

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