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How dangerous is a small amount of radioactive material?

  1. Jul 11, 2017 #1
    Last year in a Intro to Radiation Oncology lecture I was sitting in on, a physics professor at my school said that all a terrorist (or otherwise bad guy) would need to do to kill or at least harm a bunch of people is take a small amount of radioactive material and hide it somewhere in a desk. He said many people in whatever offices this was done in would eventually get sickened or killed by this little bit of material from coming near it every day when they went to work.

    I'm wondering if he was completely full of it, or if this is completely true, or anything in between. If it is, how wide a radius would the danger zone be, depending on the specific radioactive material? Please fill free to specify the specific radioactive atoms and the distances to them you think would be dangerous in this way.

    As for the reason why I'm wondering, part of it is curiosity, but part of it is I'm writing some fiction and I was thinking about using something like this. But I don't want to put it in if there isn't some legitimacy to it.

    Thanks to all replies!
  2. jcsd
  3. Jul 11, 2017 #2


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    It completely depends on the activity and type of radiation. Most naturally ocurring materials contain some amount of radioactive isotopes.
  4. Jul 11, 2017 #3
    Okay, let me add some detail. For the purpose of my short story (and yes it's dumb), what I need the character to be able to do is sneak in some sort of radioactive material into a highly restricted office area, for the purpose of finding out which of those "people" there are immune to the effects (whoever this "person" is will be the one the Ominous "They" is seeking). In other words, I need every person who works there except an alien masquerading as a human to get sick.

    So, is that, aside from an alien who is immune to radioactive effects, something that is reasonably possible in our universe? If so, what kind of material would do the trick?

    EDIT- also thanks for answering.
  5. Jul 11, 2017 #4
    I'm hoping something like a cubic centimeter of Plutonium would work for this plot line, but I know next to nothing about this topic.

    EDIT- reading this article, maybe Plutonium won't work.

    Seems to have a short range, basically needing to be inhaled if I understand it correctly.
    "Plutonium predominantly emits alpha particles – a type of radiation that is easily stopped and has a short range. It also emits neutrons, beta particles and gamma rays. It is considered toxic, in part, because if it were to be inhaled it could deposit in the lungs and eventually cause damage."

    I'm thinking I'll need something with a shorter half-life, based on this:
    "The different isotopes have different “half-lives” – the time it takes to lose half of its radioactivity. Pu-239 has a half-life of 24,100 years and Pu-241’s half-life is 14.4 years. Substances with shorter half-lives decay more quickly than those with longer half-lives, so they emit more energetic radioactivity."

    Obviously I'll keep searching but if someone knows the search is futile that would be appreciated, so I can brainstorm some other way to accomplish the plot ends.

    Thanks again.
  6. Jul 11, 2017 #5

    Vanadium 50

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    How dangerous is a small amount of poison?
  7. Jul 11, 2017 #6
    Well, what I need is for that small amount to be dangerous over a large area (on the order of 30 feet or so).

    If that's not possible, then if it were dangerous for only a radius of two or three feet I could make it work by making the character in my story have to plant little pieces in each desk at this place.

    EDIT- that actually might be more interesting, because then I can add more tension as the "hero" commits this heinous crime for the greater good. Each desk can have a different little spy-type situation.
  8. Jul 11, 2017 #7
  9. Jul 11, 2017 #8
    First, your professor is generally wrong, since small (low activity) sources aren't very dangerous. The median lethal dose for ionizing radiation is ~5 gray (500 rads). That's a big dose.

    You are right, you need a short half-life material. A strong gamma source, something like they use to radiograph piping welds. That's a dangerous source. See
    Your plot will also need a delivery system so that the person placing the source isn't over exposed.
  10. Jul 11, 2017 #9


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    Story-wise, you might be able to achieve the same result (kill or sicken humans but not aliens) by surreptitiously exposing (spraying?, putting on door knobs?) the group with an infectious biological agent (like some germ or virus).
  11. Jul 11, 2017 #10


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    If the person has physical access to the rooms, a volatile material (radioactive dust) would work much better than something hidden in a desk.
    You can't control the dose reliably, so I guess lethal doses would be accepted by this person? Leave a lot of polonium-210 everywhere.
    A few thousand atoms of potassium decay in a human every second - completely from natural sources. You need high dose rates to have health effects, especially if they should occur over a short time (not years).
  12. Jul 12, 2017 #11
    Thanks for the replies everyone. I'll think this over and hopefully have something cool.

    True but using radioactive elements seemed kind of cool. ;)
  13. Jul 12, 2017 #12


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    If you had a large quantity of radon gas, you could pump it in the ventilation system, and every occupant would breath it in without knowing.
    A 100% atmosphere of radon gives 5.54 x 1019 Bq/m3, in which case every one would die from lack of oxygen.
    A 1% ratio should give a not too healthy mixture.
    Probably less is needed, but the conversion to Sieverts, well there I got lost.

    From where one would get so much radon is a problem though.
  14. Jul 12, 2017 #13
    Small amount in the OP is ambiguous. If it refers to the activity then gmax137 is correct (although a small activity ingested could be lethal depending on the isotope) but if it refers to physical quantity then the professor is correct. Microgram quantities of a pure radionuclide can be extremely radioactive.. Preparing near pure sources is probably not possible though but even very small concentrations can be extremely radioactive and only a fraction of a cc.

    And handling/transporting a high activity source safely would require a container of lead weighing up to several hundred Kg.
  15. Jul 12, 2017 #14
    You're right, gleem.

    But, I'm just sick & tired of the "no harmless dose" claptrap promulgated by the media, so I have started to object to it whenever I hear it. And I guess I heard it here:

  16. Jul 12, 2017 #15


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  17. Jul 12, 2017 #16
    It's not just the media. All federal/state agencies who oversee the use of radioactive materials or radiation generating equipment still subscribe to this principle. And I believe that international agencies do also although I am not sure of this. So it is an uphill struggle even though no scientific evidence actually support this view. It has been administratively convenient to assume that the effects of radiation exposure are linear with dose with no threshold.
  18. Jul 12, 2017 #17
    I can't understand why if there was a plan to murder people, than radioactive poisoning would be a good idea.
    Aggression with brute force is what works for people who are in to that.
  19. Jul 12, 2017 #18


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    The idea is to find an alien immune to radiation damage. Maybe the alien is not immune to brute force? And/Or the alien shouldn't be harmed for some reason?
  20. Jul 12, 2017 #19
    Ah, thanks for explaining, I had missed the point.
    Then maybe the alien can be detected by what brands of cosmetic it uses, and if it wears torn jeans,

    /Jk, sorry
  21. Jul 13, 2017 #20
    One could, for story purposes, hide one of the radiation sources used for pipe and weld x-rays. They use something like an artificial isotope of cesium, but they are a slug of the material carried in a heavy lead cannister with a removable panel as a 'shutter' so the radiation beam can be easily directed and restricted. It could easily be hidden in a closet in the next room over and set so the beam is directed towards where the author needs it to be. It would result in high level x-ray type damage quite evident after a day or two of exposure, if not less.

    One may need to have an excuse why there is no probem on the other side of the room, perhaps a high story in the building and exterior wall, so the beam is dissipated by distance and attenuation without causing damage.
  22. Jul 16, 2017 #21
    Thanks for the detailed suggestions. It is definitely helpful to my research.

    As to why I want to do this method, part of it is the strengths of the alien, but part of it is to prevent the alien's secret group from finding out they are about to be exposed. The idea is to cause an illness that may take a couple days for doctors to figure out, thereby giving the "good guys" the information they need in a way that is minimally invasive.

    And also it's just, in my humble opinion, something that would be interesting. I haven't seen anything like this done in this kind of lame fiction before. ;)
  23. Jul 16, 2017 #22


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    You need ~500 mSv for reliable short-term radiation effects. Just four times this dose, 2 Sv, can be fatal already, and 4 Sv will lead to very fast radiation sickness effects with very low probability to survive.
    It will be difficult to distribute the dose uniformly enough.
  24. Jul 18, 2017 #23
    Use a Cobalt 60 source used for sterilization of foods. Install it in a wall or hollow door with the open end of the shielding pointed where you want the radiation to go; although since we're talking about gamma, it's likely the only effective shielding is distance.
  25. Jul 18, 2017 #24
    I did see this article, but that's a lot of Cobolt 60 they stole.

  26. Jul 20, 2017 #25
    I can't resist jumping in here with a real-world (but non-lethal) example.

    In the school year 1960-61 I was a freshman at Stanford and I took a one-credit PE course called "Radiological Health." It was an evening class. We learned interesting stuff, and also how to use Geiger counters.

    The final exam? The instructor says, "I've hidden samples of radioactive materials around this building. Go find them, and then draw a map."

    Really. Can you imagine what kind of storm that would produce now? And no, I can't remember what the isotopes he put out were.
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