Question about radiation

  1. Hello! I'm not really into physics that much, and in school I didn't study it that much either, so this question will probaby look silly to you.

    I have a question about radioactivity:

    When an object/human being is exposed to radiation, does it continue to emit rays? Because in most documentaries or movies I watch, people who have been exposed to radiation, let's say, just hours before, can be measured with detectors and the level of their exposure can even be calculated, or at least that's what they say. Like I remember from documentaries or even movies, people who get exposed are forced to take showers to get some of the radioactive material from them, but it is also said that just the shower won't get it all off.

    My question is this, is it true that a human exposed to this material (for example, let's say a liquidator on top of the roof of Chernobyl, back in 1986) is also going to emit radiation after being exposed to it? Now this baffles me, because from what I remember from those classes, only those radioactive atoms can emit rays. Don't they have to get on top of him/inside him to still emit from his body? If so, how?

    The only possible explanation I see is air. But what if the object is solid and is radioactive? Are there still atoms floating in the air, which escaped the solid mass? Is that even possible?

    Maybe some particles coming from smoke could get on top of the clothes, but the only way to get into the body is through the mouth or nose. But if he's covering it with the gasmask, sure gas mask won't help with the rays, but shouldn't it at least protect him from the particles themselves?

    It's probably a stupid question, but keep in mind that I will only get smarter if you explain everything thoroughly. And yes, I did google about radiation, read articles but didn't see anything that would help me out on this. Thanks in advance!
  2. jcsd
  3. jedishrfu

    Staff: Mentor

    Everything exhibits nuclear decay giving off trace amounts of alpha, beta and gamma radiation. Alpha radiation is basically a charged helium atom sans electrons, beta radiation are electrons, and gamma radiation are high-energy photons ie light at a very high frequency beyond the visible spectrum and beyond x-ray frequency.

    We use Gieger counters to measure these three types of radiation and so in movies they will show people being scanned by a handheld Gieger counter. If a gieger counter detects the radiation it will have been calibrated to ignore very low levels as is normally found in everyday life. Basically it means you are emitting more radiation than is common which means you probably have been dusted with radioactive material.

    A famous story was when some workers at a nuclear plant went to work they set off the detectors going in which really baffled everyone. Eventually it was found that their home was a hot zone of radon gas that had seeped up from the ground into the basement. Now home sellers are required to get radon gas tests done prior to selling their home. If its detected then they must do radon abatement ie clean and seal the basement so radon cant get inside.
  4. Vanadium 50

    Vanadium 50 18,239
    Staff Emeritus
    Science Advisor
    Education Advisor

    Being exposed to radiation does not (except in rare instances) make you radioactive. However, one can get radioactive material on or in oneself and then track it around.
  5. As a comparison,
    In some ways, if not many, you can relate exposure to radioactive elements as similar to getting a tan from the ultraviolet rays from the sun. A certain amount of exposure will not harm you. Harm from prolonged exposure will not be felt immediately, but will develop into a sunburn, of which a slight reddening of the skin is the minimum symptom. An excessive exposure to ultraviolet will lead to skin peel and flaking, and possibly more long term irreversible effects, depending upon the length of exposure.. The correlation between skin cancer and ultraviolet light has been known for some time, and tanning lotions to screen out the ultraviolet rays have been developed for protection.
  6. Yes, I do know that everything emits those rays, but I'm asking specifically about huge doses from highly radioactive materials, like what people in Chernobyl were exposed to.

    Because technically, if the rays pass your body, that is it, you shouldn't be magically emitting more radiation from your own body than before? Of course they damage your body and DNA, but I'm asking if that person, exposed to that huge radiation dose, is going to emit more radiation than he did before the exposure? Or is that going to happen only if the highly radioactive atoms/molecules that are emitting the rays, get on/inside of him?

    As another example, one of the chernobyls liquidators get put into the hospital, and he is still in a specific ward under some protective curtains and so on, which means being near him is dangerous for others, as he is still emitting more radiation than normal from being exposed to large amounts of it, while working in liquidating the catastrophe. Why is that?
    Last edited: Jan 29, 2014
  7. sophiecentaur

    sophiecentaur 14,316
    Science Advisor
    Gold Member

    The material in your body will only become radioactive if it has transmuted into a radioactive isotope. You would need to be inside a reactor or a star for this to happen. You definitely wouldn't make it into work the next morning.

    When you are exposed to a 'lethal' dose of radiation, the changes are only chemical and genetic (plus heating). Your body can, of course, pick up atoms of radioactive substances, but that's not radiation - it's contamination (to be strictly accurate).
  8. The (urban legend?) says that the three guys killed in the SL-1 accident were buried in lead caskets (some say their hands were buried separately, not sure I believe that one). Presumably due to activation by high neutron exposure? I don't know that gamma can cause activation.

    Like sophiecentaur said, dose sufficient to cause activation is likely (certainly?) fatal in the acute sense.
  9. sophiecentaur

    sophiecentaur 14,316
    Science Advisor
    Gold Member

    Anyone who actually ingests a load of long half life radioactive material would stay radioactive for a longtime. The SL 1 page in wiki talks about a significant amount of material being released into the environment. There would be no easy way to clean out the bodies of this stuff so it could have made sense to use lead coffins. (Sounds a bit unlikely though) The neutron / gamma exposure theory is not likely, if the bodies were actually not just charred heaps. Transmutation takes ages to occur, even in the structures of reactors afaik.

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