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Testing Geiger Counters 277

thesandbender writes "My girlfriend's family lives in Japan and is very interested in obtaining geiger counters for testing food and other materials. Geiger counters are now impossible to get in Japan and are on long back order from most providers in the U.S. which makes me suspicious of anything we can get our hands on. My question is, what's the best way to test/verify a geiger counter. I know I can point it at a smoke detector and it should go off but I'm not sure what I should see on the gauge. We'd even take it to any reasonable local facilities for testing (NYC area). Any input would be greatly appreciated!"
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Testing Geiger Counters

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  • DIY (Score:5, Interesting)

    by Anonymous Coward on Monday May 23, 2011 @01:53AM (#36214706)

    If Geiger counters are hard to buy, you can make one. Here's an absolutely brilliant video on how to:

    The basic idea, and brilliance, is simple. Get a plastic scintillator and hook it up to a CCD camera. Use a time exposure to record the flashes of light, and you have a cheap and easy Geiger counter. Suitable for checking food, as well as getting an idea for the radiation around you. It's not as immediate as a real Geiger counter, but at least you have some way of seeing what's going on around you instead of being blind. The scintillators are a little hard to get retail, but very available on eBay. Cost is cheap. About $32 for a 2x2" square (which is overkill). And a simple test here is to just buy a bunch of bananas, which are naturally radioactive, though very low level.

    The next step up is to add some electronics. The NukAlert is great here. Japanese customers can find it at:

    I have no association with other than as a satisfied customer. I also don't read Japanese, so I have no idea as to what it says.

    Now, to test these suckers out, you need actual radiation. You can get low level radiation devices in the States, 5 uCurie Cs-137 sources for about $80. These are used to calibrate various instruments. I would imagine that there is a way also in Japan, given how much equipment is built there. But I'm not sure if these can be imported.



  • Re:Vaseline glass. (Score:5, Interesting)

    by Kalidor (94097) on Monday May 23, 2011 @01:56AM (#36214720) Homepage

    Or rather, they should at least give you what various safety levels are. One of the big misconceptions is that we know what is a dangerous level of radiation: in fact all we know is what is too much radiation. Back in the 50's and 60's a group of scientist were asked to provide safety information on radiation and they came up with a scale using the points of zero and you aren't gonna see the end of the week. They then drew a linear line between these points because they had little to go on, and presented it as a best guess and further research was needed to prove it's truly linear, exponential, logarithmic, or what-have-you. Since then the linear graph has become kind of dogma and various groups have picked various points across it to set their safety thresholds.

    You'll find that you have a set threshold in most Asian nations that is quite low, due to close experience and some might say paranoia in relation to the deployment of nuclear arms.
    Roughly double these guidelines, and you get what is considered safe in many European countries.
    Roughly double them once more, and now you are heading toward the Americas.

  • by antifoidulus (807088) on Monday May 23, 2011 @02:11AM (#36214802) Homepage Journal
    But are they useful for testing radiation levels in the air? I live less than 100km from the edge of the evacuation zone and really would like to go there by bicycle(almost impossible to get in by car because they have barricaded off most of the area, but from what people have said, it's pretty easy to sneak in on foot or cycle). How much risk would I actually be exposing myself too? Also, would a geiger counter help?
  • by Cyberax (705495) on Monday May 23, 2011 @02:24AM (#36214864)

    For outdoor testing Geiger counters should work just fine. You don't need to worry (much) about alpha radiation, if you are careful to not eat or drink anything from the contaminated zone and wash your clothes and shoes afterwards. Also, try to avoid dust.

    You won't encounter promptly dangerous radiation levels, even if you are near the powerplant itself. Even doses as high as 100 times the normal background level require _months_ of exposure to become dangerous, and these kinds of doses will cause Geiger counter to click continuously.

  • by SharpFang (651121) on Monday May 23, 2011 @03:44AM (#36215196) Homepage Journal

    It's smart to take the counter with you and -learn the doses-.
    The problem is radioactivity occurs in "patches". Places where water drained and dried. Plants that are strongly absorbing. Cloth in the wind, capturing dust particles.

    As for learning the doses: [] is helpful but generally, 0.1 microsievert/h is common background level, 1-10 microsieverts/h is the usual "elevarted radiation level" in deserted areas. Some of most radioactive trash in Chernobyl zone findable currently is 3 milisieverts/h. 10 milisieverts will cause detectable rise of cancer risk. Acute radiation poisoning occurs around 1 sievert.

  • by thesandbender (911391) on Monday May 23, 2011 @05:47AM (#36215650)
    1. I appreciate everyone's input about the comparative levels of radiation and I'm working with my g/f to translate the xkcd chart to Japanese to put things in perspective for her family (we'll be sending it to Mr. Munroe when we finish for him to post if he likes).
    2. We've already purchased Vaseline glass beads.
    3. I'm very interested in the detailed comments that testing is pointless b/c we couldn't get access to the equipment/environment needed to properly test and will be following those up.

    From a practical and scientific standpoint we both understand that the exposure they are subject to where they live is less than being at altitude on a flight to Japan. However her family and the country as a whole has been through a very traumatic event ... first from a force they can't predict (the earthquake) and now from one they can't really see (radioactive contamination). So why we can look at this objectively and say the exposure really doesn't amount to much unless you're near the site, they'll never be able to because of what they have been through. Realistically, if you survived a plane crash you'd probably be hesitant about getting on a plane even though the statistical chances of you being in two commercial plane crashes are practically 0. Just the way the human psyche works. Anyway, I would like to keep them from throwing money away if testing food is a complete impracticality (#3).

    Thanks for all the excellent input and we will be reviewing it throughly.
  • Re:Don't. (Score:4, Interesting)

    by Attila the Bun (952109) on Monday May 23, 2011 @06:14AM (#36215742)

    You have absolutely no chance to get anything close to it on your own, so just don't.

    I'm afraid this is pretty much true, although the hobbyist in me doesn't like to admit it.

    The amount of radioactivity you're looking for is small compared to natural background, and small even compared to the normal variations in background. To identify any un-natural contamination you'll need a detector capable of distinguishing different isotopes, in a low-background environment, and it'll need to be regularly calibrated with standard sources. That entails a lot more gear than a Geiger-Muller tube, all of which is very very expensive, not to say tricky to operate.

    With a GM counter about the best you can do is to try to measure the radioactive decay of a sample, although most relevant isotopes have very long lifetimes which will be too hard to measure. 131-iodine is easy to detect and has a measurable half-life at 8 days, but I expect the authorities would find it before you do, and anyway most of it has gone by now.

    Alternatively you might befriend a physicist at your nearest nuclear research institute. Even then he or she will need to be quite a good friend, because the time and effort involved is significant, and this kind of expensive gear tends to be permanently in-use.

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