The Hazards (and not) of Radiation

Since everyone has radiation on their minds right now thanks to the situation in Japan, and since XKCD was nice enough to post this handy chart, I thought it might be useful to put up a link to my old “basics of radiation” guide from teaching radiation labs to undergrads many years ago.

(PDF Link: Handy Facts About Radiation)

A big thing this doc tries to do is explain the difference between things which will and won’t kill you. XKCD’s diagram is good at showing you the relative dangers of different levels of “primary radiation” — things like gamma rays and neutrons hitting you directly. What it doesn’t talk about is the relative dangers of radioactive substances, which can mostly kill you by getting inside your body and continuing to emit small doses of radiation.

For reference, so far the Fukushima-Daiichi plant has mostly emitted steam with radioactive noble gases in it, which is great from a safety perspective — those decay quickly and bond chemically with nothing, so they’re probably the safest radioactive leak you could ever get. XKCD’s diagram is appropriate for those. If the core were to be breached and spray some of the heavier materials inside there, like Cesium or Uranium, the results would be much nastier.

Also, a footnote: This doc works in units of rems, while a lot of the recent news reports have used Sieverts. 1 Sv = 100 rems.

Published in: on March 22, 2011 at 10:03  Comments (4)  


  1. The pdf is good, although it took me a second to figure out that the heading was a link to it. But it’s REALLY dense reading for someone that’s not familiar with the eV. How about writing up something in more layman’s terms? I would love to be able to send it out to various family members (who think coal/oil is a safer energy source).

    • Yeah, that would be a good idea. I stuck this up just because I already had it on hand… it definitely was written for physics students, not the general public.

      If I have some time soon I may try to write that up.

  2. One of the failings I’ve been hearing repeatedly in news coverage has been non-scientists fuzzing the distinction between radiation and radioactive material. I assume the non-scientists are making this mistake honestly, out of their own confusion. Unfortunately, the scientists haven’t been clarifying the point, presumably because it doesn’t occur to them that people would be confused about it, and the non-scientists have been walking away still mistaking them for each other.

    So any clarification, in easily quotable bite-sizes, is incredibly valuable.

  3. […] recently posted a copy of my old radiation safety notes. Those were written for young physicists, so they aren’t exactly models of clarity. Since […]

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