Radiation Chart

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.

796 thoughts on “Radiation Chart

  1. The average person’s background dose is 10uSv/day, while the EPA yearly limit is 1mSv/year. So the “average person” gets 3.6x the EPA limit (?).


  2. The EPA limit is for the *additional* dose an average person allowed to receive in a year above the normal background radiation.


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  4. I’ve heard it passing that raised radiation levels had been detect a while back but it really really hard to find any actually data on what kind of raditions(they had too many lasers on and the reporter was a lieing SOB) or any actual units(per time). For those of use who do understand a little of the physics its not very reasuring when people say things like its aproximately .5mSvs of raditions or what ever cause at least I think “is that the grand total? how can you possibly know that at this point” but this chart is pritty cool. But if you could happen across a comparsison of say…. something like “the levels on the west coast rose by 2.4 bananas” that would be pritty sweet


  5. Thank you for this informative post. I have been in Tokyo since March 11th and I have always been on the lookout for clear explanations I can pass on to those without a scientific background who have let fear take over.
    Numbers have been used by medias without any clear explanation about what they really mean.
    I very much appreciate your perspective about who the real victims are, right now. So far as I can see, most of those who have been in Tokyo during the crisis focused their talks on the plight of the refugees, not on the small inconveniences we have to endure in Tokyo.


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  8. Hey. Anyone know how to make this type of chart once you have the data? What program was used?


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  16. Someone liked your radiation chart as it seems – And that someone is the “GRS”. That’s the department for “reactor safety” of the german ministry for environmental protection. Impressive, they took the interesting sidenotes out of the chart (they have no clue about the radiation levels of sleeping next to someone obviously) but otherwise publish pretty much the same chart:




  17. I don’t understand the difference between the “Extra dose from one day in an average town near the Fukushima plant (~3.5 microSv)…” and the “One-day dose (~3.6 mSv) at two sites 50 km NW of Fukushima”.

    What is the meaning of “near” if the one-day dose at 50 km is 1000 times the first one ?



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  19. Wow. Well and awesomely done chart. It’s never about the data, it’s about understanding the data, in layhuman’s terms.

    Unfortunately the terms layhumans understand seems to drop in relation to Moore’s law, so that chart’d get you the Nobel Prize for Smartness in about 30 years.


  20. Today April 12 the Japanese atomic agency has reclassified the accident. Up to now about ten percent of the radioactive material set free in Chernobyl has been set free in Fukushima. Shouldn’t you update the corresponding numbers in your figure?


  21. Actually, the EPA limit would be that PLUS the average person’s dose, wouldn’t it?


  22. I’m gonna print this and put it on a wall at my office. Is really impressive what you’ve done with the information. As many have said here before, this is something that the common people can understand… or at least try :P


  23. @ein pythaogaeer: The reclassification reflects new analysis of the total amount of airborne radioactivity released. Most of that radioactivity was released in the early part of the crisis, during the hydrogen explosions. The chart is based on doses that people would get, which in turn was based mostly on direct radiation measurements at various places inside and outside the evacuation zone.

    It’s a common misunderstanding that the reclassification means the accident has gotten worse–it has not, there was just initially more radiation released than was thought. However, since people were evacuated quickly, it doesn’t mean that more people got higher doses than originally thought. Furthermore, the isotope of greatest concern, I-131, has decayed by now to less than 1/16 of its initial activity. (This is because I-131 has an eight-day half-life). The dose rates in the evacuation zone and on the reactor site have been decreasing steadily.

    I hope this helps people understand the meaning of the reclassified INES level a bit better.


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  26. All radiation is not the same. Radiation from natural sources are known as beneficial, while what industry “creates” (plutonium) thru nuclear power plants is extremely toxic.


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  28. Randall,
    I love this chart. I especially liked the comparison of normal operational emission of coal v. nuclear. I found your chart while searching for better free porn.

    I have been unable to locate information to support an interesting thing I heard in a lecture years ago: total cumulative release from all nuclear power plants including chernobyl and 3mile assdents (sic) is far less than total cumulative release from all coal burning plants, ever. Maybe something for xkcd.com/radiation/v2. I wonder if Fuku will tip the scale?

    (I apologize for the remainder of this post in advance.)

    And, I just must disagree wholeheartedly with what “Matt Colburn says: April 21, 2011 at 10:39 am, “… radiation from natural sources are known as **beneficial**, while what industry “creates” … is toxic.”

    I can see that you have a point to make but, … in this case:

    Natural ≠ Beneficial and Industrial ≠ Toxic.

    (In case of unicode failure those should be not-equal signs.)

    While I am certain to stick my foot in fully here …

    I contend that the application as well as the levels of duration, intensity, distance, and protection predicate benefit v. toxicity where nature v. industry do not at all in any way do any such thing ever even a little bit.

    Cases to think about:

    Naturally-occurring Radon gas buildup in/under a dwelling causing illness to dwellers. Dwellings are bad.

    Naturally-occurring Radium or some such thing decayed from Uranium in the water supply of a small town and a larger city I have lived in. Yep, it was on my water report! Testing authority said lovely, safe water according to EPA and, it tastes great. Hmmm.

    Naturally-occurring, solar-radiation effects, both good and bad, upon unprotected people, also, both good and bad. (The Sun, responsible for life, health, illness, and death is the biggest damn “Natural” nuclear reactor and omni-directional transmitter of every wavelength of energy in the neighborhood! Only 1 AU away!)

    Naturally-occurring cosmic radiation effect upon unprotected astronauts and, I gather, mostly indirectly upon us surface dwellers due to fallout from upper atmospheric process which mostly protects us from the direct rays. Somewhere in between for high flying airline passengers.

    Safety-industry-created smoke and carbon monoxide sensors with alarms for saving lives. (Teensy little bits of plutonium or the like in these sensors might eventually have adverse effects upon you if swallowed but, …)

    Medical-industry-created radiation for flow tracing, imaging, and irradiation of cancer to make us live a little longer.

    War-industry-created nuclear weapons to make our evil enemies not live any longer. Hey! It could be a good thing! … OK, … it’s bad. But they could be used to blow up a deadly ass-troid like in that movie! No, the other movie.

    Power-industry-created nuclear plants, sans earthquake/tsunami/equipment failures/operational fuckups, providing power for our microwave ovens. OK, bad!

    Power-industry-created coal-burning plants providing wonderful power while slowly layering the planet with low-level radioactive waste, even after scrubbing the exhaust! A polished turd is still a turd.

    Food-industry-created irradiation for longer term preservation of foodstuffs so a few of us can lament our demise in caves and shelters a little longer while the nuclear winter rages on and the planet dies around us and the cockroaches laugh.

    Archaeological-industry-created carbon dating techniques for future generations, if any, to determine in which century we really fucked it bad.

    Natural radiation all good? Industrial radiation all bad? Nope!

    So, Matt, you can see that beneficial v. toxic do not directly correlate to nature v. industry when thinking about ionizing radiation. I take away a different message completely: Without natural rad we wouldn’t exist. Industry rad has surely complicated things for us all. Either one is a mixed bag of both beneficial and toxic effects. Radiation, natural or man made, is a necessary but tricky bitch. Always be careful.


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  30. Mr. XKCD, your site and your graph have been featured in the UK’s “The Guardian” and the Austrian “Der Standard”. Congrats! :)


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  33. Have I ever mentioned how much I love your (Mr. Munroe) intelligence. If I didn’t have xkcd I’d sufficiently deficient of it! This is just a thanks!


  34. I think it would be neat to add the exposure that you’d receive standing in front of the US Capitol Building. I found a source that said the yearly exposure was 850 µSv. The Capitol wouldn’t be licensed to operate as a nuclear power plant!


  35. @stevie
    The article stevie linked to is a bunch of hyperbolic BS…

    Chernobyl exposed 220,000 people to doses over the lowest amount linked to cancer, and killed 28 people outright, and still only caused approximately 4000 cases of cancer.

    Since Fukushima only exposed around 200 people to similar doses, we can really only expect around 4 people to get cancer from the exposure.

    Similarly, while chernobyl released 50% of the reactor mass in soot from the inferno, including the longer lived decay products. Fukushima released only the water soluble iodine 131 and cesium 137, and the iodine only has a half-life of 4 days, so it is already a non-threat to returning residents. (most of the exclusion zone has already been lifted, with the exception of a small area with large amounts of cesium contamination.)

    And quite frankly, it is hard to consider the plant operators who caused the accident “victims of radiation”.

    The fukushima reactors are the same design that was successfully contained at 3 mile island, and if they had just bit the PR bullet and released the contaminated gas buildup like at TMI, then there would have been no hydrogen explosions to contaminate the surrounding area and damage the containment structures.


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  38. A friend of mine said his 9th grade daughter asked him why don’t we use the space suits used to walk on the moon to protect against radiation at Fukushima’s reactor for repair? Can any one answer?


  39. Re: Jack –
    The space suits did not provide adequate radiation protection. The early astronauts that went to the moon have suffered from many complications due to the increased radiation they were exposed to.


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