There’s a lot of discussion of radiation from the Fukushima plants, along with comparisons to Three Mile Island and Chernobyl. Radiation levels are often described as “<X> times the normal level” or “<Y>% over the legal limit,” which can be pretty confusing.
Ellen, a friend of mine who’s a student at Reed and Senior Reactor Operator at the Reed Research Reactor, has been spending the last few days answering questions about radiation dosage virtually nonstop (I’ve actually seen her interrupt them with “brb, reactor”). She suggested a chart might help put different amounts of radiation into perspective, and so with her help, I put one together. She also made one of her own; it has fewer colors, but contains more information about what radiation exposure consists of and how it affects the body.
I’m not an expert in radiation and I’m sure I’ve got a lot of mistakes in here, but there’s so much wild misinformation out there that I figured a broad comparison of different types of dosages might be good anyway. I don’t include too much about the Fukushima reactor because the situation seems to be changing by the hour, but I hope the chart provides some helpful context.
(Click to view full)
Note that there are different types of ionizing radiation; the “sievert” unit quantifies the degree to which each type (gamma rays, alpha particles, etc) affects the body. You can learn more from my sources list. If you’re looking for expert updates on the nuclear situation, try the MIT NSE Hub. Ellen’s page on radiation is here.
Lastly, remember that while there’s a lot of focus on possible worst-case scenarios involving the nuclear plants, the tsunami was an actual disaster that’s already killed thousands. Hundreds of thousands more, including my best friend from college, are in shelters with limited access to basic supplies and almost no ability to contact the outside world. If you’re not sure how to help, Google’s Japan Crisis Resource page is a good place to start.
Edit: For people who asked about Japanese translations or other types of reprinting: you may republish this image anywhere without any sort of restriction; I place it in the public domain. I just suggest that you make sure to include a clear translation of the disclaimer that the author is not an expert, and that anyone potentially affected by Fukushima should always defer to the directives of regional health authorities.
xkcd 
@Lin, you are confusing micro and milli sieverts. A year at the stated dose for Fukushima is equivalent to 1277.5 micro sieverts or 1.2775 milli sieverts. i.e. a little over a third more that normal background dose, and way under the 100 milli sievert cancer risk threshold.
Brilliant chart by the way, will be using it in my teaching from now on.
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I would like a higher quality image for printing. 🙂
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Worked in the regulatory field for 33+yrs.
Good presentation for those who will take the time to reason thru.
Everybody wants simple answers for radiation.
Very complex. If you do not wish to take the time to comprehend,
you will be misguided/frustrated.
Too many experts with weak understanding of topic. Just because
one works with radiation producing equipment does not qualify one
to be competent in understanding radioactive materials.
Media folk desire simple answers. Radiation by nature a complex topic.
Thanks!
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Trivial question I’m sure, but in Ellen’s post she mentions that (thought I think we’ve all heard about) lead being a typical form of shielding from radiation. Is the lead content in good old fashion lead based paints, and found in some old glass panes sufficient enough to provide any sort of shielding. Not that I’m about to repaint my house or buy new/old lead glass. Just more of a idle curiosity thing.
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This chart has been linked in The Guardian – a major UK paper!
http://www.guardian.co.uk/commentisfree/2011/mar/21/pro-nuclear-japan-fukushima
The chart does put things into perspective. As a scientist, I am appalled at the rampant hyperbole and wild misinformation out there about nuclear processes.
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I passed this on to the director of our Nuclear Engineering Technology program. He said he was going to print it in color and post it for the students.
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The Edmonton sun printed this today, didn’t give credit though.
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very cool! but why did you add the “radiation worker 1 year dose limit” (50mSv) twice?
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Congratulations! Your chart just got a mention by New York Times science writer Andy Revkin on his widely-read Dot Earth blog:
http://dotearth.blogs.nytimes.com/2011/03/23/the-dread-to-risk-ratio-on-radiation-and-other-discontents/?hp
And for everyone complaining about one aspect of this chart or another — READ THE BLOG POST: “I’m not an expert in radiation and I’m sure I’ve got a lot of mistakes in here, but there’s so much wild misinformation out there that I figured a broad comparison of different types of dosages might be good anyway.”
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I know this is meant as an informal chart, but Knight repeats an oft-made mistake about cell phones and cancer. That cellphones do not produce ionizing radiation does exclude a causative link to cancer! Does smoking produce ionizing radiation? (Well, actually, one does inhale some radioactive isotopes in cigarette smoke, but you see my point).
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What’s even more interesting about the guardian article is that Monbiot was a die-hard nuke opponent in 2000.
http://www.guardian.co.uk/environment/2000/mar/30/energy.nuclearindustry?INTCMP=ILCNETTXT3487
His view had softened to neutral by 2006.
http://www.guardian.co.uk/commentisfree/2006/jul/11/comment.environment
And now he’s pro-nuclear. I guess the moral of the story is that people can and do change their minds when faced with facts, but it takes years and requires patience and humor.
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@Elemental
Though some may read it that way, a strict interpretation of Munroe’s statement doesn’t say any such thing. He simply states two separate facts; that cellphones do not produce ionizing radiation, and also that they do not cause cancer. There are no causal terms or implied relations between those two declarations.
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Lies, damn lies and then statistics. Firstly, The averaging done is meaningless as alluded to by the exposure time period over which the dose was gained being most important. Secondly, The particle nature of exposure for a radio emmiter is of most importance as well as the type of radiation which the chart completely ignores. Gamma, alpha, beta. An ingested beta emmitter such as I-131 will likely kill a younger person with cancer at trivial doses compared to the chart. A particle of Plutonium a beta emitter can pass through the body with a high or low exposure level dependent upon the mass and do nothing at all! Yet if it lodges in the body you are a goner.
Now if you live in a fanstasy land and believe that the radition particles coming out of the accident site are uniformly distributed, do not lodge/accumulate on surfaces or plants, are not ingested by animals, and stay in circulation while ever diluting in the air/water/earth, then the chart is somewhat comforting from a statictical viewpoint, which is likely your statistical viewpoint the further you live from the nuclear accident. If however as a casual observer you live near the accident site, say within 500 miles or more and it was obvious to you that the explosion from the #3 reactor totally shredded the nuclear fuel rod containment pool and launched the debris 1000+ feet skyward, then your “results may vary.” But your feeling better now because some useful idiots are feeding you a diet of nuclear statistics along with Uranium, Plutonium, Iodine, Strontium and other long half life isotopes you are ingesting and being exposed to for the rest or your life.
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As pointed out at http://docsgreen.blogspot.com/2011/03/fukushima-nuclear-power-and-coal.html any seismic event severe enough to cause major problems at a nuclear power station will probably cause thousands of times more mortality and morbidity due to building collapses, tsunami, etc.
Also, annual fatalities from coal-fired power production and its fuel cycle are dozens to thousands per year in the U.S. (depending on whether you count premature mortality from particulate emissions). Premature deaths from nuclear power production in the U.S. is on average one or less. In Japan it might be a bit more (there have been some deaths already at Fukushima, and there were some a few years ago from a fuel-reprocessing accident).
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@ JamesP:
“Firstly…” That’s true. I do believe the chart states that results have varied widely. In fact, I believe the chart says, in relevant cases (Chernobyl 2010 strikes me as an example), that these are measured readings and levels may vary.
“Secondly…” Ah, but that is the beauty of the Sievert unit. 1 Sv = 1 Gy.W, where W is a weighting factor _for type of radiation and tissue exposed_. So when talking about the dose to lungs of a chest Xray, we really can equilibrate it to dose to thyroid from radioactive iodine therapy (a recognised and incredibly useful medical technique).
Finally, I do believe there is more information should people be interested. And the chart does provide links, something I haven’t seen yet in the popular press.
Except, of course, the article in Melbourne’s _The Age_ newspaper, which led me here.
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Just wanted to toss this in here even though it seems a little late to fix it, but you have the dose limit for emergency workers in lifesaving operations mixed up with the limit for non-lifesaving. It should be 750 mSv, not 250. Straight from your source: http://www.ornl.gov/sci/env_rpt/aser95/tb-a-2.pdf
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A version scaled to fit on A4 paper would be nice too…
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I see people still not quite getting it when it comes to ingestion/inhalation of radioactive material…
Randall’s chart does capture intake of radioactive material because it is in terms of “effective dose”
Effective dose accounts for the differences in inhaling/ingesting alpha/beta/gamma emitting radioactive material. That is the whole purpose of the effective dose units: Sv, rem
Effective dose accounts for the fact that alpha particles cause ~20 times more damage internally than gamma emitters.
All dose calculations for internal dose are in terms of effective dose.
If I inhale Cs-137 and the calculated effective dose is 1 mSv, that is almost exactly the same as if I was zapped with an x-ray machine that was set to deliver a 1 mSv dose to my body. I say “almost the same”, because the 1 mSv internal dose is actually the dose integrated over a 50 year period — the internal Cs-137 dose might actually be 0.5 mSv the first year, 0.2 mSv the second year 0.1 mSv the third year, etc.
It’s a little different when you have a nuclide that seeks out a particular organ e.g. Iodine to the thyroid or Strontium to the bones, but the same principle applies… If I inhale/ingest enough I-131 to deliver a 10 mSv dose to my thyroid, it is the same as if I go to the radiotherapy dept at the hospital and have them set their accelerator to deliver 10 mSv to my thyroid.
Nobody is trying to say that exposure to 37kBq of Cs-137 sitting on a table is the same as ingesting/inhaling 37kBq of Cs-137.
If you spend 24 hours sitting ~30 cm from a 37 kBq Cs-137 source you would get a dose of ~0.001 mSv — inhaling the same amount would result in an effective dose of ~0.25 mSv and ingesting it would be ~0.5 mSv (using current U.S. regulatory Annual Limits on Intake — more current internal dosimetry models generally result in lower dose calculations)
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Just thought I’d chip in on one point. You’ve listed a Mammogram at 3Sv, but that is closer to the equivalent dose to the organ (see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2430752/ where 2-2.5 mSv is given). After weighting and summing all the equivalent doses to the organs, the effective dose for modern digital mammograms is more like 0.3 mSv.
@James P: perhaps you should do some more learning before commenting. Most plutonium isotopes are Alpha emitters. Only a few of the heavier one emit betas.
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Very reassuring. Nonetheless, as an engineer, I still have to say it seems DAMNED stupid to build titanically-powerful machines that tend to melt and/or blow up, rather than simply grinding to a halt, when deprived of constant supervision. And which, in such a not-improbable event, have a high likelihood of spreading not just radiation, but radioactive particulates that remain toxic for a thousand years and can render huge areas of geography unsafe for human habitation.
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RADIATION DOSE CHART: > living within 50 miles of a nuclear power plant for a year (0.09 µSv) it`s wrong,
it should read for an hour < right?
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@Reinhard
No, that’s a year Nuclear power plants while functioning properly do not produce much in the way of radiation.
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Thanks for that great graphic. It was the basis for a very similar graphic, on p.24 of the News section of the Ottawa Sun print version March 23 2011 (It’s in Canadia). The person who put the infographic together even kept “(such as the Colorado plateau)” which I thought was hilarious. xkcd was noted as a source. It really was a super way to visualize the ‘scale’ of it all.
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@PhoenixGI:
The lead in paint/windowpanes/lining your fridge (thanks, Indiana Jones) isn’t going to do much — I’m talking big, heavy lead bricks (and those are fun to move around the facility). Lead’s shielding abilities are dependent on its thickness. If you’re not that curious, stop reading here. But if you want something a lot in-depth:
Different materials shield things differently. Alpha particles (He nuclei) can be stopped by a piece of paper, because they are big and interact easily with things. As a result, they’re rarely a concern, as long as they stay outside the body — if they’re inside, they’re 20 times worse for you than gamma rays or beta particles. The sievert takes this into account by means of a quality factor.
Beta particles (electrons or positrons) can be stopped by a centimeter of plastic or wood. They actually interact with lead and other high-Z materials to produce *more* radiation via bremsstrahlung, and so placing some plastic in front of your lead might help. However, with enough lead, it won’t be a problem.
Gamma rays (extremely high-frequency EM radiation) are shielded by lead, travel the furthest, and are the primary cause of external exposure. The intensity of the gamma rays through a shield is described by the equation I = I_0 e^(-u*x), where I_0 is the initial intensity, u (mu, usually) is the linear attenuation coefficient of the material, and x is the distance travelled. I/I_0 can be replaced with dose rates without changing anything.
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I hate to burst your bubble James… oh wait, I LOVE to burst your bubble… but anyone who is living close enough to the plant at Fukushima to be adversely affected by ingestion and/or inhalation of alpha and beta particles have been evactuated and/or administered potassium iodide. The largest concentration of isotopes in the area have been confirmed to be iodine-131, which has a half-life of 8 days. All isotopes with longer half-lives are in negligible concentrations.
Maybe you should stop watching Fox News and get some accurate information before you comment.
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I am sure someone has already pointed this out…but I Really can’t read through 400 comments to see…
This chart is just…wrong. Wonder about motivation of creator. The Japanese Gov (certain to be downplaying disaster) was reporting 400 microsieverts PER HOUR on the 17th. Not 3.5 per day. Yearly dose racks up a lot faster at that rate. It is a shame that supposed journalists fall for these types of distortions.
I see that someone has at least pointed out that once you have INGESTED the radionuclide, your dose rate properly measured in sieverts goes WAY up. Distance does not help this, by the way, because once ingested, the distance of the emitter is in microns. This is why an alpha particle outside the body can be stopped with paper, but inside the body is responsible for most tobacco death.
The 8 day half life of I-131 the media is starting to tout is also a lie. That is it’s Radioactive half life. Its biological half life is MUCH longer and is well known in medicine. Also, for the half life to matter, you would have to know when the exposure stopped. Hasn’t yet.
This chart is either deliberate disinformation or the work of someone who may have some knowledge of rudimentary high school physics but knows NOTHING about ingested radionuclides.
The most simple reading of even the humble wikipedia page on what a sievert is should make clear that the “official” number TEPCO is giving is meaningless in the unit chosen. Little comment in the mainstream about what nuclides are actually being released (about 100 different types of unstable atom in the average nuke plant) or in what quantities. Without this data, NO reputable scientist would attempt to assess risk for anyone at any distance.
It’s all about what particle you or your food eats or breathes in. So do you feel lucky? People have every right to demand an end to the fission scam. It is NOT a SOURCE of energy and certainly not green.
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Wow… I’ve enjoyed reading the comments just as much as the chart itself. Thanks, folks! 🙂
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@D.Aster: The chart was produced in collaboration with an actual reactor professional and cites its sources. I don’t see any sources in your rant. And what are your credentials?
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@D. Aster,
If you can show me how the biological half-life for a radionuclide can be even 1 second longer than the nulide’s radioactive half-life, I will send you $50 US via whatever route you wish: check, cash, paypal, amazon wishlist, etc. Then I will immediately nominate you for a Nobel in physics (or perhaps biology).
Read Randall’s post below the chart – it explains his motivation and sources of information.
(also read the footnotes in the chart they explain things like where the info came from)
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@D.Aster — where was that 400 uSv/hr figure from? Location is very important. If you look at my post, I explain how distance affects radiation dose. The number on the chart is from a site 50km NW of Fukushima. If that 400 uSv/hr figure was from the control room, or even the site boundary, that’s actually *LESS* radiation than Randall’s number.
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Okay, for all those talking about the dose due to inhaled or ingested radioactive materials: I’ve added a section on my page about how doses from those are compared to external doses, with an additional linked explanation of how to do the math yourself. Internal and external doses *are* comparable, and there’s a commonly-used way to do so.
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This chart is now available as a SVG on Wikimedia Commons.
http://commons.wikimedia.org/wiki/File:Exposure_chart-XKCD.svg
This should make it easier to translate and more convenient to print on large pannels.
Thank you for an excellent document.
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@elemental
@aether
One could say that if you smoke a cellphone, one does inhale some radioactive isotopes.
If you you see my point 😉
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Wow, thanks for the chart! I love reading xkcd.com and this helps me understand the basic idea, even if some of this is inaccurate.
I did not know we could have radiation from everywhere. The thought simply did not occur to me. But being aware allows me to appreciate this in a new light.
Good job and thanks for raising awareness!
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@ D.Aster
You said: “The Japanese Gov (certain to be downplaying disaster) was reporting 400 microsieverts PER HOUR on the 17th. Not 3.5 per day.”
The chart says: “One-day dose (~3.6mSv)…”
mSv = millisieverts
μSv = microsieverts
400 microsieverts = 0.4mSv, entirely compatible with a one-day dose of 3.6mSv.
Prefix fail!
You said: “I see that someone has at least pointed out that once you have INGESTED the radionuclide, your dose rate properly measured in sieverts goes WAY up.”
Yeah, true. Gosh, I wish Randall’s chart had included a variety of examples comparing the effective doses of both internal and external exposures…
Reading fail!
You said: “The 8 day half life of I-131 the media is starting to tout is also a lie. That is it’s Radioactive half life. Its biological half life is MUCH longer and is well known in medicine. Also, for the half life to matter, you would have to know when the exposure stopped. Hasn’t yet.”
…Umm. Do you have any idea of what a “half-life” is? The half-life of radioisotopes ejected from a given event is utterly independent of “when the exposure stopped”. Nothing matters except when, and how much, was spewed forth. One half-life later, half of the material has decayed, so there’s half as much to be exposed to.
Science fail!
You said: “The most simple reading of even the humble wikipedia page on what a sievert is should make clear that the “official” number TEPCO is giving is meaningless in the unit chosen.”
What unit would you prefer? The sievert does not ignore different forms of radiation or the effects of external vs. ingested exposure; it encapsulates them. The figures released are for external exposures at certain locations. Different figures could, and no doubt will, be found to measure ingestion of any lingering isotopes in the medium to long term.
Measurement fail!
Your failure is complete.
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Good chart, but disappointed to see a basic error with the Chernobyl data –
The dose/hour in front of the Chernobyl plant is 6μSv, not 6mSv. Big difference!
The source states the value correctly.
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You could include “allthe doses in the red chart combinend” = so much yellow blocks …
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@D. Aster:
> The Japanese Gov (certain to be downplaying disaster) was reporting
> 400 microsieverts PER HOUR on the 17th. Not 3.5 per day.
Others already pointed out your errors here:
1) The 3.5 μSv/day you quote from the chart is not at the reactor, but at an average town NEAR the reactor. The 400 μSv/hour you quote is from the facility. Apples and oranges.
2) The chart does show 3.6 mSv/day aka 3600 μSv/day measured at two sites 50km from the reactor. This is roughly 1/3 of your quoted 400 μSv/hour that was measured directly at the facility. Thus, the chart does show that some areas not immediately next to the facility have received larger exposures.
Thus, no distortions there.
> The 8 day half life of I-131 the media is starting to tout is also a lie.
> That is it’s Radioactive half life. Its biological half life is MUCH longer
> and is well known in medicine. Also, for the half life to matter, you
> would have to know when the exposure stopped. Hasn’t yet.
3) OK, let’s take this on. The problem with I-131 is that it concentrates in the thyroid. Once the thyroid is fully saturated with Iodine, further exposure will not increase the amount of iodine in the thyroid. This is the point with the iodine pills that so many people (not those in Japan) are wasting their money on.
4) The radioactive half life and the biological half life are totally unrelated. The biological half life is how long the iodine remains in the body before it is excreted. However, this DOES NOT affect the radioactive half-life. Indeed, the radioactive half life is 8 days, in the body or not. Thus, once exposure stops, the amount of RADIOACTIVE iodine in the body will drop by half every eight days, simply because the radioactive iodine is decaying. The body will still excrete iodine at a much slower rate, but when you’re talking about exposure to radiation, you don’t care about that. You only care about the radioactive isotope, which is dropping by half every eight days.
5) As long as the exposure is ongoing, once the thyroid is fully saturated, the continuing exposure will only guarantee that the thyroid remains fully saturated, that radioactive iodine keeps getting incorporated into the thyroid at the rate that it decays, keeping a constant concentration. (In the absence of iodine pills.)
6) People who are actually exposed will get the iodine pills, which will prevent and mitigate the worst consequences of I-131 exposure.
Thus, no distortions there either. No lies at all. You just misunderstood.
> This chart is either deliberate disinformation or the work of someone
> who may have some knowledge of rudimentary high school physics
> but knows NOTHING about ingested radionuclides.
Actually, you just don’t know what you are talking about. Sorry.
> The most simple reading of even the humble wikipedia page on what
> a sievert is should make clear that the “official” number TEPCO is
> giving is meaningless in the unit chosen.
7) TEPCO seems to be reporting in Bq/cm3, looking at their web page. This is not *meaningless*, but it does not translate directly into a unit of human exposure to damaging radioactivity, aka, Sievert.
> Little comment in the mainstream about what nuclides are actually
> being released (about 100 different types of unstable atom in the
> average nuke plant) or in what quantities. Without this data, NO
> reputable scientist would attempt to assess risk for anyone at any
> distance.
Here, you’re being extreme. As long as measurements are provided in Sv, by someone, scientists can make reasonable risk assessments. You don’t need to know the isotope mix for this.
> People have every right to demand an end to the fission scam.
Here you reveal you have an entrenched point of interest that is likely to distort your analysis of the facts.
> It is NOT a SOURCE of energy
And here you leave rationality behind. How is nuclear energy not a source of energy, when it is demonstrably providing large amounts of energy for many countries? Or are you, instead, just suggesting that yes it is a source of energy, but it is chosen so countries have an excuse to enrich uranium, as others in this thread have alleged.
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@D. Aster,
I was re-reading my post and I probably owe you $50 US…
I always think of biological half-life as meaning effective biological half-life (because when dealing with radioactive material, that is what one is concerned with…)
Your reasoning is still wrong, because it doesn’t matter how long the biological half-life is if the radiological half-life is shorter — it just means that the effective biological half-life is ~= to the radiological half-life.
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@Eddie and @Peregrine (and everyone else who has posted!)
As a high school Physics and Chemistry teacher, thank you for your comments! I can never stress enough to students that as future citizens and consumers they need to understand science! Because, as we all know, statistical results can easily be spun in favor whichever point of view you support!
Thank you!
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Well I guess that ends my plan to eat 1,600 bananas.
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From the chart:
“Extra dose from one day in an average town near Fukushima plant (~3.5 uSv as of March 17, varies quite a bit).”
From the reference cited in the source page for the chart for March 17:
http://www.facebook.com/notes/international-atomic-energy-agency-iaea/iaea-briefing-on-fukushima-nuclear-emergency-17-march-2011-1400-utc/202624509767343
“Dose rates to the north-west of the nuclear power plants, were observed in the range 3 to 170 microsievert per hour, with the higher levels observed around 30 km from the plant.
You know, taking the lowest value from a range where the highest value is larger than the lowest by 50X and calling this ‘the average’ is just dishonest. Calling a dosage ‘daily’ when in fact it is hourly is 24 X dishonest.
I haven’t checked the other claims about supposed exposure at ground zero at Chernobyl or ‘background’ (actually fallout) at the Japanese sites. I suspect these are equally, uh… trying not to say dishonest again since that’ too repetitive…. uh…. creative!
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