Japanese infants are receiving far more radiation dose more than I have been expecting. I apologize for my earlier optimism.
According to a press release, http://mdn.mainichi.jp/mdnnews/news/20110324p2a00m0na037000c.html, "The Nuclear Safety Commission of Japan (NSC) has made its first announcement on the estimated amount of radiation exposure in areas located around 20 and 30 kilometers from a quake- and tsunami-crippled nuclear plant in Fukushima Prefecture. The commission concluded the accumulated amount of radiation exposure per person was 500 millisieverts in areas within the "indoor standby zone" between 20 and 30 kilometers from the Fukushima No. 1 Nuclear Power Plant -- where people have been instructed by the government to remain indoors to avoid radiation risks -- over the course of 12 days following the March 11 disaster."
That is 50 Rem, for U.S. readers. The U.S. limit for dose to the skin is also 50 Rem. But, most of this dose is to the thyroid gland in the neck. And the calculation is for infants.
So, what does this mean?
Fortunately, the data indicates that there is little risk of effects at this exposure level. Unfortunately, there is not enough data to be definite about that. Thyroid doses are less dangerous than whole body doses, by about a factor of 20. http://www.oecd-nea.org/rp/chernobyl/c04.html But, infant doses are more dangerous, partly because they are growing quickly, and partly because they will live long enough to develop cancer or other diseases.
I wish that I could be more optimistic.
Chernobyl area residents got about 1.4 gray of dose, or 140 Rem. So that is about three times as much as Japanese infants near the plants have gotten - and the total they are likely to get is about what Chernobyl residents got.
That is far more than I have been expecting. I apologize for my earlier optimism.
But, these doses are calculated for infants, and the dose is to the thyroid. As best I can tell, no one else will get doses that high.
Therefore, cancers will be fewer than were caused by Chernobyl.
And it is still true that U.S. residents will receive far less dose. Washington State has a web page for airborne radiation, showing that, even with the releases from Japan, dose rates here are below the average annual rates from last year. http://www.doh.wa.gov/Topics/japan/monitor.htm
Saturday, March 26, 2011
Sunday, March 20, 2011
What is Radioactivity?
Radioactivity may seem mysterious, but it has been part of our world at least since the Fall of Man.
When Marie Curie noted that uranium could make air conductive to electricity, she dubbed it "radioactive".
The more prosaic story that I was taught in grammar school was, a scientist found that uranium could make a radio click. Thus uranium made radio receivers active. Uranium is radio - active.
Many other naturally-occurring materials are radioactive as well.
When Marie Curie noted that uranium could make air conductive to electricity, she dubbed it "radioactive".
The more prosaic story that I was taught in grammar school was, a scientist found that uranium could make a radio click. Thus uranium made radio receivers active. Uranium is radio - active.
Many other naturally-occurring materials are radioactive as well.
Nuclear disaster and natural catastrophe
Science Daily http://www.sciencedaily.com/ has a linked article on the Japanese earthquake and the resulting nuclear disaster. http://www.newsdaily.com/stories/tre72g65z-us-japan-quake-meltdown-specialreport/
Except for one sentence, I agree with the article. The article says "As the first pictures of the destruction around the northern town of Sendai were beamed across Japan and around the world in the hours after the quake, authorities initially said they had safely shut down the four nuclear plants closest to the earthquake and tsunami zone.
It wasn't true. With no power to the plant's cooling system, the water that circulates around the fuel rods inside the six reactors at Fukushima had already begun to boil off. Within a few hours authorities declared a "nuclear emergency situation" at the plant. While no radiation release had been detected, they said, residents around the plant should evacuate."
It was 93 percent true. The control and safety rods entered the core, and fission went from 93 percent of design power to 0.01 percent power. Fission product decay remained at 7 percent power. That is how nuclear engineers define "safely shut down", so the statement was true. But, that 7 percent power continued to heat the fuel rods, and that heat needed to be carried away. It was carried away - safely - until fifteen minutes later when a 30 foot tsunami hit and wiped out the fuel supply for the emergency diesel generators.
Then, a natural disaster became a catastrophe. And the nuclear event became a disaster.
But, so far, the nuclear disaster has not become a catastrophe.
The current situation is:
The reactors at Fukushima Daini are recovering, with three of the four damaged and in a Level 3 event state. Those three reactors may, or may not, restart after damage is repaired. The fourth has a better chance
Three of the six reactors at Fukushima Daiichi are in serious trouble, with probably molten fuel in the cores; they are in Level 5 event states; the other three reactors were in an outage, and fuel was already removed from one when the quake struck. Fuel in then other three is safe. (see http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300624909P.pdf)
I would be astounded if reactors # 1 , 2, or 3 ever operate again. Meanwhile, the fuel storage pool for #4 was dried out - either by sloshing during the quake or by a leak. The stored fuel overheated, the cladding reacted with remaining water, and there was a hydrogen explosion outside the containment which destroyed the reactor building. Water was restored by fire cannon and helicopter drop.
All six reactor cores are inside containments, and all six containments are functional, although unit #2 has suspected damage.
As long as the containments remain reasonably intact, Japanese citizens have no cause for fear - though they may be very fearful. Many times, smaller earthquakes than this cause deaths from heart attacks. The nuclear risks may also cause heart attacks. Preventing those fear-induced medical events is a major purpose of these posts.
For United Sates residents, there is no reason to fear. As noted below, the radioactivity within the fuel cores has decayed to less than 0.14 percent of full power, so even if something could somehow vaporize the cores and the containments, the result would be less than one in 50 of what Chernobyl was. And the evacuation to 12 miles makes it less than one in 1,000 of Chernobyl. That means, less than four cancers - worldwide.
As to the radioactivity now reaching U.S. shores, the level is below what we get when we eat bananas. That's right, bananas. Eating one banana shows up when nuclear professionals get our annual "whole body count". Every time they do this, I have the same count - one body :-). The "whole body count" (http://en.wikipedia.org/wiki/Whole_body_counting ) measures the radioactive material in the human body. If too much potassium-40 shows up, the technician asks how many bananas we eat. Bananas have lots of potassium, some of which is radioactive potassium-40. The benefits of potassium far outweigh any negative effects of the radiation. So, eat your bananas, and take courage - this "radioactive cloud" is less than one billionth of what we should worry about.
Except for one sentence, I agree with the article. The article says "As the first pictures of the destruction around the northern town of Sendai were beamed across Japan and around the world in the hours after the quake, authorities initially said they had safely shut down the four nuclear plants closest to the earthquake and tsunami zone.
It wasn't true. With no power to the plant's cooling system, the water that circulates around the fuel rods inside the six reactors at Fukushima had already begun to boil off. Within a few hours authorities declared a "nuclear emergency situation" at the plant. While no radiation release had been detected, they said, residents around the plant should evacuate."
It was 93 percent true. The control and safety rods entered the core, and fission went from 93 percent of design power to 0.01 percent power. Fission product decay remained at 7 percent power. That is how nuclear engineers define "safely shut down", so the statement was true. But, that 7 percent power continued to heat the fuel rods, and that heat needed to be carried away. It was carried away - safely - until fifteen minutes later when a 30 foot tsunami hit and wiped out the fuel supply for the emergency diesel generators.
Then, a natural disaster became a catastrophe. And the nuclear event became a disaster.
But, so far, the nuclear disaster has not become a catastrophe.
The current situation is:
The reactors at Fukushima Daini are recovering, with three of the four damaged and in a Level 3 event state. Those three reactors may, or may not, restart after damage is repaired. The fourth has a better chance
Three of the six reactors at Fukushima Daiichi are in serious trouble, with probably molten fuel in the cores; they are in Level 5 event states; the other three reactors were in an outage, and fuel was already removed from one when the quake struck. Fuel in then other three is safe. (see http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300624909P.pdf)
I would be astounded if reactors # 1 , 2, or 3 ever operate again. Meanwhile, the fuel storage pool for #4 was dried out - either by sloshing during the quake or by a leak. The stored fuel overheated, the cladding reacted with remaining water, and there was a hydrogen explosion outside the containment which destroyed the reactor building. Water was restored by fire cannon and helicopter drop.
All six reactor cores are inside containments, and all six containments are functional, although unit #2 has suspected damage.
As long as the containments remain reasonably intact, Japanese citizens have no cause for fear - though they may be very fearful. Many times, smaller earthquakes than this cause deaths from heart attacks. The nuclear risks may also cause heart attacks. Preventing those fear-induced medical events is a major purpose of these posts.
For United Sates residents, there is no reason to fear. As noted below, the radioactivity within the fuel cores has decayed to less than 0.14 percent of full power, so even if something could somehow vaporize the cores and the containments, the result would be less than one in 50 of what Chernobyl was. And the evacuation to 12 miles makes it less than one in 1,000 of Chernobyl. That means, less than four cancers - worldwide.
As to the radioactivity now reaching U.S. shores, the level is below what we get when we eat bananas. That's right, bananas. Eating one banana shows up when nuclear professionals get our annual "whole body count". Every time they do this, I have the same count - one body :-). The "whole body count" (http://en.wikipedia.org/wiki/Whole_body_counting ) measures the radioactive material in the human body. If too much potassium-40 shows up, the technician asks how many bananas we eat. Bananas have lots of potassium, some of which is radioactive potassium-40. The benefits of potassium far outweigh any negative effects of the radiation. So, eat your bananas, and take courage - this "radioactive cloud" is less than one billionth of what we should worry about.
Friday, March 18, 2011
Still Not a Chernobyl
Japan has raised the event level from four to a five on a scale of seven.
This is frightening many.
But, the releases so far are one billion times lower than Chernobyl, and the worst it can become now is one million times lower than Chernobyl.
As has been reported, the cloud reaching California is one billion times below the levels to create health risks.
Is anyone afraid of paint fumes from five miles away? This is about how frightened we should be.
Because the 160 plant employees have controlled the releases, and the containments are reasonably intact seven days after the reactors were shut down, the radioactive inventory is 0.2 percent of the original operating power level. So, if the fuel melts, then evaporates, and the containments vanish - even with this, the release will be less than 2 percent as bad as Chernobyl.
So, no more than 20 cancers could be caused in Japan, and no health effects in any other country.
Please pray for those 160 employees, and especially for the 50 employees at the worst-stricken nuclear plants.
This is frightening many.
But, the releases so far are one billion times lower than Chernobyl, and the worst it can become now is one million times lower than Chernobyl.
As has been reported, the cloud reaching California is one billion times below the levels to create health risks.
Is anyone afraid of paint fumes from five miles away? This is about how frightened we should be.
Because the 160 plant employees have controlled the releases, and the containments are reasonably intact seven days after the reactors were shut down, the radioactive inventory is 0.2 percent of the original operating power level. So, if the fuel melts, then evaporates, and the containments vanish - even with this, the release will be less than 2 percent as bad as Chernobyl.
So, no more than 20 cancers could be caused in Japan, and no health effects in any other country.
Please pray for those 160 employees, and especially for the 50 employees at the worst-stricken nuclear plants.
The Great Beyond
Japan's nuclear situation is not - not - as horrible as the media report. As a nuclear safety engineer, I am appalled at the false statements by "experts" who do not understand. Check out blogs.nature.com/news/thegreatbeyond/2011/03/high_radiation_levels_seen_far.html
The maximum measured contamination is 17 millirem per hour, 30 kilometers from the nuclear palnts, or 500 times natural background - but, it will be reduced by decay, and total doses to people will not likely go past three chest x-rays.
The maximum measured contamination is 17 millirem per hour, 30 kilometers from the nuclear palnts, or 500 times natural background - but, it will be reduced by decay, and total doses to people will not likely go past three chest x-rays.
Thursday, March 17, 2011
Fukushima Info
ScienceDaily has this info from Japan.
http://www.newsdaily.com/stories/tre72g65z-us-japan-quake-meltdown-specialreport/
http://www.newsdaily.com/stories/tre72g65z-us-japan-quake-meltdown-specialreport/
Latest Japan Nuclear info
This http://www.youtube.com/user/NEINetwork youtube link has the latest from the Nuclear Energy Institute
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