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Testing Geiger Counters

samzenpus posted more than 2 years ago | from the rads-are-bad dept.

Japan 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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Geiger Counter (2, Informative)

Palmsie (1550787) | more than 2 years ago | (#36214596)

In case you didn't know what it was (like me):
Wikipedia:
A Geiger counter, also called a Geiger-Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a Geiger-Müller tube. Each particle detected produces a pulse of current, but the Geiger counter cannot distinguish the energy of the source particles. Geiger counters are popular instruments used for measurements in health physics, industry, geology and other fields, because they can be made with simple electronic circuits.

Re:Geiger Counter (0)

Anonymous Coward | more than 2 years ago | (#36214616)

I was using one of those when I was visiting Chernobyl. Overrated I think, could had done without too.

Re:Geiger Counter (1, Insightful)

Anonymous Coward | more than 2 years ago | (#36214666)

In case you didn't know what it was (like me):

You didn't know? Really?!

Call me cynical but for a moment there it looked like you were just karma whoring.

Re:Geiger Counter (1, Offtopic)

johanatan (1159309) | more than 2 years ago | (#36214726)

But, for him to be karma whoring, there'd also have to be a significant number of slashdotters who don't know (which is quite the unlikely case). So, either he didn't know; or he over-estimated the number of slashdotters who don't know.

Maybe I'll go for some karma too: (3, Funny)

Chrisq (894406) | more than 2 years ago | (#36214758)

But, for him to be karma whoring, there'd also have to be a significant number of slashdotters who don't know (which is quite the unlikely case). So, either he didn't know; or he over-estimated the number of slashdotters who don't know.

Arse:
1. the buttocks
2. the anus
3. a stupid person; fool

Elbow:
1. The joint or bend of the arm between the forearm and the upper arm.
2. The bony outer projection of this joint.

Well its about ask likely as a slashdotter not knowing what a Geiger counter is.

Re:Geiger Counter (2)

osu-neko (2604) | more than 2 years ago | (#36215104)

You didn't know? Really?!

I thought I did, but upon reading OP's description, I can safely say I knew in the same sense at someone who knows an "internal combustion engine" is what makes cars go (i.e. knows that it does), rather than knowing in the sense of someone who knows what it actually is (engine that works by sparks igniting fuel, pushing pistons in cylinders, turning the crank shaft, etc.). I knew that a Geiger counter is a device that detects radiation and makes that clicky-noise. I knew what it does, but not, really, what it is. Most of what the posted paragraph contains was new information to me.

Vaseline glass. (4, Informative)

Kenja (541830) | more than 2 years ago | (#36214602)

A common way to test a Geiger counter is to use a small sample of Vaseline glass such as a bead. The glass contains a small amount of uranium oxide which should be detectable.

Re:Vaseline glass. (1)

mustPushCart (1871520) | more than 2 years ago | (#36214648)

They dont just want one to detect radiation, they want one to accurately tell them how much radiation is actually present. They should also know exactly how much radiation is harmful over what period of time. A faulty counter or even poor knowledge of radiation can be just as harmful by underestimating the amount of radiation than by overestimating the amount of radiation and displacing your life / spreading panic among everyone else.

Re:Vaseline glass. (4, Informative)

Kenja (541830) | more than 2 years ago | (#36214676)

As I said, Vaseline glass is often used as a calibration source. The CPM for many sources and quantities is well documented. True, if you get a random piece off eBay for a few dollars you may not know what its reading is supposed to be, but it should be consistant between different devices.

Re:Vaseline glass. (0)

Anonymous Coward | more than 2 years ago | (#36215190)

Kenja you are correct. Good point.

Re:Vaseline glass. (0)

Anonymous Coward | more than 2 years ago | (#36215202)

No, you didn't see it was used as a calibration source.

Re:Vaseline glass. (5, Interesting)

Kalidor (94097) | more than 2 years ago | (#36214720)

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.
 

Re:Vaseline glass. (0)

Anonymous Coward | more than 2 years ago | (#36214800)

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.

I was under the impression that the US followed IAEAs recommendation of 1mSv/year.
In the European country where I live the background radiation is about 3mSv/year because of high levels of uranium and radon in the ground. Because of this the recommended max doseage is set to 4mSv/year.

Re:Vaseline glass. (2)

deroby (568773) | more than 2 years ago | (#36215022)

In the European country where I live the background radiation is about 3mSv/year because of high levels of uranium and radon in the ground. Because of this the recommended max doseage is set to 4mSv/year.

After rereading this a couple of times I really have to ask for confirmation :

So :
* "by convention", 1 mSv/year is considered "safe"
* the location you live in outputs about 3 times that value (natural source)

But, because we "know" where it comes from, and because it's "natural" radiation, it doesn't count as being harmfull and the safety limit is upped to those 3 mSv/year PLUS the "by convention" 1 mSv/year ??

??? What kind of logic is that ???

Shouldn't they just put the limit to 3 mSv/year for all people living in that area ? (it's kind of non-practical to remove all background radiation) + pay extra attention to potential effects due to already having 3 times the 'conventional' limit to live with ?

Re:Vaseline glass. (3, Informative)

Lefty2446 (232351) | more than 2 years ago | (#36215188)

After rereading this a couple of times I really have to ask for confirmation :

So :
* "by convention", 1 mSv/year is considered "safe"
* the location you live in outputs about 3 times that value (natural source)

But, because we "know" where it comes from, and because it's "natural" radiation, it doesn't count as being harmfull and the safety limit is upped to those 3 mSv/year PLUS the "by convention" 1 mSv/year ??

??? What kind of logic is that ???

Shouldn't they just put the limit to 3 mSv/year for all people living in that area ? (it's kind of non-practical to remove all background radiation) + pay extra attention to potential effects due to already having 3 times the 'conventional' limit to live with ?

So nobody who lives in that area qualifies for X-rays, scans etc?

I know the following is XKCD but it's still quite informative:
http://blog.xkcd.com/2011/03/19/radiation-chart/ [xkcd.com]

Re:Vaseline glass. (1)

drolli (522659) | more than 2 years ago | (#36215338)

The logics behind that is simple: each effort you make has positive and negative consequences. All levels on the orders of some mSv/year are *safe* in the sense that if you apply that radiation to 10000 people, you probably wont be able to see the effects - even statistically. This means if you have a population of 100000 where you have to decide to move them - or not - you have to take into account that the adverse effects may impose a bigger problem than the radiation. The psychological stress and possible loss of the workplace will probably cause an rate of death via suicide or alcoholism which far outweighs the effects of increasing the radiation level from 2mSv/year to 4mSv/year.

However it may make sense to keep the rule not to try to expose 30000000 people to such a radiation levels. And this is exactly why i think that the persons responsible for not venting the reactors/the building immediately should go to prison.

Re:Vaseline glass. (4, Informative)

umghhh (965931) | more than 2 years ago | (#36215302)

The question about what is a safe level is a really tricky one especially as it involves statistics i.e. it is usually not: if you cross this line you will be shot but rather if you cross this line you may shorten your life by this much or become a customer of cancer clinic in course of your life but that you can also without additional exposure. There are different people and different effects depending also which part of the body got hit the most. On top of it if certain radioactive materials get into your body the effects depend on what these were and which part of the body is affected the most. Plutonium is highly toxic by itself and getting already small amounts into your system will probably kill you or made you uncomfortable (as with kidneys' failure uncomfortable for instance). On top of it you have empirical data from people working with extreme levels of radiations and these are not straight forward either - members of army units that cleaned up the shit in Chernobyl are mostly dead by now and those living are mostly sick yet President Carter took part in similarly adventures operation in Canada at Chalk River Laboratories in 1952 and he is still well.

I guess the bottom line is that you just need to ensure thatbloody thing is working in the first place i.e. shows something and then compare the results - assuming majority of the food stuffs are safe then measure those and see whether there is change.

Re:Vaseline glass. (1)

SomePgmr (2021234) | more than 2 years ago | (#36214830)

If it's just to see if the thing is working, I've heard a lantern mantle works. Also old radium watches. I'm sure someone can confirm or deny.

Re:Vaseline glass. (1)

TheLink (130905) | more than 2 years ago | (#36214942)

If the food you're testing is more radioactive than a pile of brazil nuts then you probably don't want to eat it, especially if it's normally not supposed to be as radioactive as a brazil nut :).

http://www.orau.org/PTP/collection/consumer%20products/brazilnuts.htm [orau.org]

Wait, what? (3, Funny)

MrEricSir (398214) | more than 2 years ago | (#36215060)

Vaseline is radioactive?! So you're saying I shouldn't be using it to, you know, wax my carrot?

Re:Wait, what? (1)

Anonymous Coward | more than 2 years ago | (#36215074)

You mean wax your MUTOR?

Re:Wait, what? (0)

Anonymous Coward | more than 2 years ago | (#36215156)

So you're saying I shouldn't be using it to, you know, wax my carrot?

Not if you're worried about it turning into a monster!

Go to FUKUSHIMA (0)

Anonymous Coward | more than 2 years ago | (#36214606)

go to one of the nuclear plants, go to the core.
If the readings are off the scale, it works!!

Re:Go to FUKUSHIMA (1)

siddesu (698447) | more than 2 years ago | (#36215214)

Even better is to use the calibration source that is customarily attached to each device. Mine has one (in a lead case) that provides three levels of emission and a section on calibration in the user manual. I would suppose any usable instrument will have one as well.

Don't get one. (4, Insightful)

Anonymous Coward | more than 2 years ago | (#36214622)

99% of the general population can't operate one. Measuring radiation is not like measuring signal strength of an electromagnetic field. People forget that it's radioactivate _matter_ emitting radioactivity, something akin as if you had tiny mobile towers all over the place. There is a large difference between a weak emitter stuck to your geiger counter and a powerful source a lot further away, but radioactivity-wise at a specific point they are indistinguishable. There is a large difference between different kinds of radioactivity aswell.

Geiger counters are useless for someone without at least a basic education in nuclear physics.

Re:Don't get one. (1)

freeman-sr (1842222) | more than 2 years ago | (#36214670)

Well, I guess somebody could point out those basics instead of discouraging people to even try. :)

Re:Don't get one. (3, Insightful)

DDLKermit007 (911046) | more than 2 years ago | (#36215018)

No, not really, Geiger Counters are honestly something not meant for public use. If their family is that freaked out about the radiation, and don't trust the government, they need to jump ship like all the other weird foreigners that panic instead of being selfish and gobbling up the supply of Geiger Counters officials could be snatching up. Unless they are getting food that was raised next to the reactors, the dosage is going to be laughable. They'll get more radiation on their flight back to the states than from any ammount of cumulative food they are going to eat. Morons the whole lot of them.

Re:Don't get one. (2)

jamesh (87723) | more than 2 years ago | (#36214678)

Geiger counters are useless for someone without at least a basic education in nuclear physics.

I wouldn't go that far. If you have two cans of beans in front of you and pointing the geiger counter at one gives you the same reading as background and pointing it at the other makes the thing go crazy then I think it's pretty clear which is the safer[1] one to eat.

Likewise, with a geiger counter it should be easy to tell the difference between a lettuce still full of radioactive fallout and one that's at least been rinsed off :)

[1] that's 'safer', which doesn't necessarily imply safe...

Re:Don't get one. (1)

DrXym (126579) | more than 2 years ago | (#36214754)

Geiger counters are useless for someone without at least a basic education in nuclear physics.

I wouldn't go that far. If you have two cans of beans in front of you and pointing the geiger counter at one gives you the same reading as background and pointing it at the other makes the thing go crazy then I think it's pretty clear which is the safer[1] one to eat.

Likewise, with a geiger counter it should be easy to tell the difference between a lettuce still full of radioactive fallout and one that's at least been rinsed off :)

[1] that's 'safer', which doesn't necessarily imply safe...

In the former case what is the likelihood of that? Has the food even been canned in an affected region? If so, choose one which wasn't. I assume even if it was then there would be restrictions and possibly an outright ban on contaminated food. In the latter, if the remedy is simply rinsing the food, then rinse the food again. It wouldn't be a bad idea to rinse cans too since it would be dust that is the issue. Also buy foods which are unlikely to be affected by the outbreak, e.g. imported meat & fish & vegetables.

Buying a geiger counter seems like an absurd overreaction.

Re:Don't get one. (1)

jamesh (87723) | more than 2 years ago | (#36214816)

Also buy foods which are unlikely to be affected by the outbreak, e.g. imported meat & fish & vegetables.

I think that's the whole point... slapping an "Imported Goods" sticker on something doesn't make it imported, but makes it hard to tell the difference. Do you really trust your supply chain all the way to the end?

Re:Don't get one. (1)

DrXym (126579) | more than 2 years ago | (#36215176)

I don't live in Japan and have no idea how their food labelling works. However in the EU all food stuffs display a country of origin and in the case of unprocessed meats, eggs you can usually trace the product right back to the farm the animal was reared on.

Re:Don't get one. (1)

mwvdlee (775178) | more than 2 years ago | (#36215268)

So if you stick a copied label on a new egg, has the single chicken retroactively layed double the amount of eggs? Or was the label invalid?

Re:Don't get one. (5, Insightful)

the_raptor (652941) | more than 2 years ago | (#36214828)

Unless you are picking lettuce from the grounds of the Fukushima nuclear power plant that scenario isn't going to happen (and anyway you should ALWAYS wash produce, the pesticides etc that get used aren't exactly great for you either).

From what I have read the fallout is at such low levels that it is within the bounds of variation in background radiation (ie mostly the levels are below what you would get from living in a high altitude area like Denver, Colorado). Unless you are in the immediate vicinity of the leaking reactors you aren't going to get a dose that has immediate effects, and just ignoring the whole situation will cause less damage then regularly eating junk food.

People in general are fucking terrible at risk assessment, and that is before you use the word "radiation".

There are several different types of radiation detectors with varying degrees of accuracy, and the type you can scrounge around and get now are probably not worth the money even if you put in the time and effort to calibrate and understand it.

Re:Don't get one. (1)

Anonymous Coward | more than 2 years ago | (#36215130)

Also a geiger counter (to the best of my knowledge) won't allow you to determine what element the food might be contaminated with. You might get easy off and just have a bit of Caesium-whatnot and have hardly any effect on your health or you might have bad luck and there is a bit of Plutonium-whatnot in it and have a 50x higher risk of cancer in the next ten years than you would given just a dose of Caesium. Or something along these lines. Radiation != Radiation. Therefore the readings from a geiger counter are fairly useless if you think about taking in any food that might be contaminated.
Granted Plutonium is highly unlikely to be in the food since it's pretty heavy and shouldn't be carried very far but I personally doubt it is inconceivable for any troubling element to go into the food chain. After all not every single product gets checked and checks probably are based on radiation alone and don't detail where that radiation is coming from.
So the choice should be between trusting the government/food chain or buying from a different place altogether.

Re:Don't get one. (1)

Registered Coward v2 (447531) | more than 2 years ago | (#36215342)

Geiger counters are useless for someone without at least a basic education in nuclear physics.

I wouldn't go that far. If you have two cans of beans in front of you and pointing the geiger counter at one gives you the same reading as background and pointing it at the other makes the thing go crazy then I think it's pretty clear which is the safer[1] one to eat.

Likewise, with a geiger counter it should be easy to tell the difference between a lettuce still full of radioactive fallout and one that's at least been rinsed off :)

[1] that's 'safer', which doesn't necessarily imply safe...

Not necessarily - all you know is one is emitting more penetrating particles than the other - whose particles are probably already penetrating your skin as well. The other can could be loaded with alpha emitters which are blocked by the can. Once you eat them, however...

As a result, your readings don't amount to a hill of beans when it comes to assessing safety...

Radiation badge (0)

Anonymous Coward | more than 2 years ago | (#36215102)

Which is why radiation badges were invented. Doesn't require much intervention or thought. Might not be perfect for this application, but they are relatively cheap and plentiful. Probably set for higher doses than required, but it's an idea.

G counter test (2)

dentext (117409) | more than 2 years ago | (#36214652)

test G counters with a mantle for a gas lantern, like Colman. it's a strong short range source, so when you hold it an inch or 2 away, it'll be loud. anything thats that loud, worry about. less than that, don't worry about. That's what I learned in a Nuke Med R&D/mfg facility.

Re:G counter test (0)

Anonymous Coward | more than 2 years ago | (#36214682)

coleman now sells here in europe non-radioactive gas mantles

Re:G counter test (1)

Anonymous Coward | more than 2 years ago | (#36214712)

That only works if you can find old mantles that contain Thorium. New mantles don't.

Kearny Fallout Meter (0)

Anonymous Coward | more than 2 years ago | (#36214656)

Here are homebrew fallout meter designs (link to PDF at the bottom of the page): http://en.wikipedia.org/wiki/Kearny_Fallout_Meter

More info: http://www.oism.org/nwss/s73p921.htm

I realize that does not help you calibrate your Geiger counter, but it does offer another measurement for validation of your current calibration. It also is a great thing to share with other people who do not have Geiger counters.

Testing (1)

Anonymous Coward | more than 2 years ago | (#36214692)

I would not use a smoke detector to test a Geiger Counter. The Americium 241 is an alpha decay and chances are your Geiger counter won't be sensitive to alpha particles.

If you want to verify that a Geiger counter works, hold it beside some salt substitute (Potassium Chloride). If it starts clicking more than background, it works. Old orange Fiestaware pottery works as well.

Easiest places to test geiger counters (1)

TubeSteak (669689) | more than 2 years ago | (#36214694)

1. Your local college/university science department
2. Local Fire Dept or the nearest Fire Dept hazmat team

My personal experience is that geiger counters come with a sample for calibration, but apparently yours didn't.

Re:Easiest places to test geiger counters (0)

DDLKermit007 (911046) | more than 2 years ago | (#36215032)

They haven't actually purchased one yet, or they would know this. The honestly have no clue about them, and shouldn't be using one. They just know allot of noise=bad. I would bet good money the family is not Japanese.

Some types of smoke detectors. (4, Informative)

fahrbot-bot (874524) | more than 2 years ago | (#36214696)

I know I can point it at a smoke detector and it should go off ...

Well, perhaps an Ionization [wikipedia.org] type detector, but probably not other types, like Optical.

Re:Some types of smoke detectors. (2)

Jane Q. Public (1010737) | more than 2 years ago | (#36214890)

Not even then. If your radiation counter goes off near a smoke detector, throw that thing out and get a new one, ASAP!

Yes, most ionization-type detectors contain a small amount of Americium 241. It is radioactive. BUT... it is housed in a metal can that has angled louvers so that air can pass through, but there is no line-of-sight to the radioactive material. All radiation emitted by the Americium should be (and normally is) fully contained by the can.

The only way you should be able to measure radiation that is above background levels would be to disassemble the can.

Re:Some types of smoke detectors. (0)

Anonymous Coward | more than 2 years ago | (#36215066)

>disassemble the can.

and ingest the contents,right?

DIY (5, Interesting)

Anonymous Coward | more than 2 years ago | (#36214706)

If Geiger counters are hard to buy, you can make one. Here's an absolutely brilliant video on how to:
http://www.youtube.com/watch?v=G6Q7VfWdgEg

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:
http://www.nukalert.jp/

I have no association with nukalert.com 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.

HTH.

--ES--

Re:DIY (5, Informative)

maxwell demon (590494) | more than 2 years ago | (#36214826)

If Geiger counters are hard to buy, you can make one. Here's an absolutely brilliant video on how to:
http://www.youtube.com/watch?v=G6Q7VfWdgEg [youtube.com]

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.

That's a radiation detector, but it's not a Geiger counter.

Of course, what the poster wants most probably is just a radiation detector (and the Geiger counter is just the one radiation detector he knows of), so your advice isn't wrong; it's just wrong to call that a Geiger counter.

Re:DIY (2)

SharpFang (651121) | more than 2 years ago | (#36215352)

The basic idea is brillant. The effect, not quite so.

Read the comments on the video and follow the links. Plastic scintillator simply does not emit enough light to be captured by a consumer-grade camera. Scientific camera, correct temperature, darkness achieved by thick black plastic - yes, it works. Best of consumer-grade night-vision cameras, 1h exposure - nothing. half-inch plywood appears "transparent" for night streetlights, but the scintillator remains dark. Sources so strong that they make alarm go off while enclosed in lead container - scintillator still not visible. This is doable but NOT with consumer-grade cameras, and as such, the whole concept of "cheap, commonly available dosimeter" falls.

Geiger counters are not really useful (4, Informative)

Cyberax (705495) | more than 2 years ago | (#36214708)

Geiger counters are not really useful for food testing. They generally won't detect alpha radiation which is the most harmful type. Besides, elevated concentration of caesium or strontium can be easily mimicked by elevated levels of natural K-40.

They really need to stop worrying about food testing. Or get a professional radiometer (which will cost $$$$).

Re:Geiger counters are not really useful (3, Interesting)

antifoidulus (807088) | more than 2 years ago | (#36214802)

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?

Re:Geiger counters are not really useful (4, Interesting)

Cyberax (705495) | more than 2 years ago | (#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.

Re:Geiger counters are not really useful (1)

antifoidulus (807088) | more than 2 years ago | (#36214968)

You've convinced me, I'm going to take a brief trip into the evacuation zone as soon as I can. I just have to make sure to post the pictures anonymously as getting caught going in there could potentially get me deported :P

Re:Geiger counters are not really useful (0)

Anonymous Coward | more than 2 years ago | (#36214976)

Enjoy your looting!

Re:Geiger counters are not really useful (1, Interesting)

SharpFang (651121) | more than 2 years ago | (#36215196)

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: http://xkcd.com/radiation/ [xkcd.com] 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.

Re:Geiger counters are not really useful (2)

Cyberax (705495) | more than 2 years ago | (#36215224)

10 millisieverts doesn't cause detectable elevated cancer level, it's about 100 millisieverts. And background level is 0.1-0.2uSv/hr.

PS: I really liked the old "Roentgen" unit, it's so much easier to remember: 10R is elevated cancer risk, 100R is mild acute poisoning, 500R is LD50. And natural level is around 10-20 uR/hr.

Re:Geiger counters are not really useful (1)

Registered Coward v2 (447531) | more than 2 years ago | (#36215330)

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?

Not really - you need a device to suck air through a filter and then test the filter. Once you get the counts, wait a while and retest to get the half life and try to see what the source may be.

Calibration Source? (0)

Anonymous Coward | more than 2 years ago | (#36214734)

What is the issue? (1)

Anonymous Coward | more than 2 years ago | (#36214742)

Testing the efficacy of radiological test equipment is a solved problem as of 60 years ago. What is the issue?

If you can put aside your overt hatred of anything "US" in origin, viable counters with NRC approval (of known efficacy bearing Federal approval) are a few mouse clicks away - far less keystrokes involved than posting this "request for information" on an Internet blog.

Since you posted this on ./, one can assume you are wanting to do this on the cheap, with Linux, or without "anything US", etc. If so, you are limited to Russian units from E-bay or surplus Yugoslav detectors from 1991- which are most likely inaccurate due to calibration drift, based on chemical dosimetry, or a valve-based unit weighing more than the average Walmart patron.

You need to pick your poison.

Do the research, pony up the money or suffer buyers remorse.

Samples (2)

PsychoticSpoon (1580137) | more than 2 years ago | (#36214744)

I have a Geiger counter from the 1960's that includes a small sample of radioactive material on its side for testing and calibration. The manual states that there should be a certain number of clicks per second, and based on the half life of the material, it looks like it still works fine. Amazon [amazon.com] also sells small samples of uranium that have a specific number of clicks per second that you can use to test your equipment.
Other than that, there is a normal level of background radiation that amounts to about 14 clicks per minute if no other material is available, but this might not be viable in your area.
Actually, I don't really have a pressing need for my Geiger counter, and it sure sounds like you need it more than me. If you want, I'd be happy to ship it. Let me know.

Re:Samples (1)

kiberovca (524346) | more than 2 years ago | (#36215050)

Shouldn't all of the Geiger counters come with exactly that - an small sample of radioactive material for calibration? I thought that is the norm even for today's devices. I guess the OP should ask in the shop where he/she is buying.

Try your local university (1)

hisperati (1408819) | more than 2 years ago | (#36214748)

Try contacting someone at your local university in physics or chemistry. They will have access to common radioactive test sources (like Na-22) which they use in standardized amounts for calibration. They may be willing to help and can give you the exact information you need. Or maybe you could buy a small Na-22 sample from a laboratory supply shop online? I don't know. I don't think you need a license and it will come in a small 'safe' plastic disk. Then you can read online how to use it as a reference source.

I used to do this for a living! (0)

Anonymous Coward | more than 2 years ago | (#36214760)

I worked at the regional radiation service for a while, one of my dutys was to calibrate counters.

It was actually trivially easy, we had a few calibrated sealed sources (it's nearly 20 years ago so don't ask me which particular isotopes) and took readings at 20cm from the source. This was fed into a program (that I wrote) which calculated the expected rate from the source based on the time & the half life and produced a calibration certificate.

There were some other checks too, electrical safety, light permiablity of scintillation tubes (nothing more funny than testing one that's faulty - point it at any light source and you get a massive reading, scares people shitless!)

Best place to start to find out if this is a service that's offered is to go to the nearest hospital with a medical physics department (there's normally one with a major radiotherapy department) they should be able to point you in the right direction.

Re:I used to do this for a living! (0)

Anonymous Coward | more than 2 years ago | (#36215070)

My GrandF was USSR geologist and used Geiger counter for his needs, he told me that main issue was to calibrate the counter. For calibration they used very very small amount of isolated radioactive material which was kept in safe, isolated container. Calibration was done by opening the hole of container. This is what they were doing for professional use, don't know about domestic...

Suggested GC and some info (0)

Anonymous Coward | more than 2 years ago | (#36214762)

The Geiger counter I have, and recommend:
http://www.gammascout.com/ [gammascout.com]

"The DOE's position is that there is NO safe dose of radiation (linear, no cut-off model) ."
http://en.wikipedia.org/wiki/Orders_of_magnitude_(radiation) [wikipedia.org]

Nice comparison of radiation doses:
http://xkcd.com/radiation/ [xkcd.com]

bananas (0)

Anonymous Coward | more than 2 years ago | (#36214772)

Buy some bananas.

Not all smoke detectors use radiation (1)

Oryn (136445) | more than 2 years ago | (#36214782)

Be careful. Quite a lot of modern smoke detectors use LED light beams to detect smoke. These will not trigger much of a reading from your Geiger Counter

Re:Not all smoke detectors use radiation (1)

DDLKermit007 (911046) | more than 2 years ago | (#36215048)

Nor should a normal detector. The can should completely isolate the material from being detectable by a GC.

A tiny bit on radiation readings (2)

meerling (1487879) | more than 2 years ago | (#36214784)

I can't say anything about calibrating, but an easy way to check it's functionality and great way to demonstrate science is as follows:

Go outside, preferably during the day, take a reading. This is background radiation, you live in it your entire life, it varies, and the sun puts out a lot so it will be lower during the night. Don't panic, Hollywood, like usual, got the science wrong. (Think about it, how often do cars actually explode in real life. Yeah, Hollywood science is useless.)

Great, now go inside a building, take another reading. If you've got access to a nice sturdy concrete building with a basement, or some caves, those are even better. See how much it dropped? That's because of the building (or earth and solid rock) blocking the radiation coming from the sky.

Now keeping an eye on the changing levels is probably what someone in Japan really wants, but you might have to ask someone that's in the science department at a university to find out what the readings were before the Fukishima incident.
Also, distance from source will effect intensity by a lot! So a chunk of radioactive material 1 meter away will read much much higher than one 10 meters away. Since the sun and other stars are so far away, the measly distance of the Earths diameter won't make much different to those, so unless there's a flare or something, only the terrestrial sources will be a big worry.

Anyhow, this is all high school stuff, or it used to be before they started dumbing down science in schools, so it's easy to find books about it in most libraries.

As a side note, you can NOT detect a modern unexploded nuke with a geiger counter, their cases are so heavily shielded you can use them for radiation shielding.
Again, Hollywood is so full of it. :)

Re:A tiny bit on radiation readings (0)

Anonymous Coward | more than 2 years ago | (#36215076)

This is plain wrong and misleading. The amount of detection measured indoor and outdoor varies wildly, depending from several factors. Just to make a few examples:
If sands making up your soil come from the dissolution of granite you will measure a higher radiation background, than when measuring radiation emitted by limestone sands, the reason laying in the amount of thorium and uraniun minerals usually found in granite. If the building where you do indoor measurements is built over a fault and/or it is poorly vented, you will find plenty of radiations due to the presence of radon. I could go on further showing counter-examples to all your statements, but it is not worth of it. For sure your knowledge of radiation physics is more negligible than the amount of my background radiation (and I live very far from Fukushima).
.

Re:A tiny bit on radiation readings (4, Informative)

Teun (17872) | more than 2 years ago | (#36215242)

You are very wrong in assuming radiation is less inside a building, especially granite has a high natural radiation and it might be incorporated in the concrete.

Certain kinds of plaster board are made from material recovered at cement furnaces and it too has a quite high radiation level.

Radiation measurements are part of my job, I'm certified for it and I can tell you making a useful measurement of foodstuff requires expensive gear and a lot of time.

A simple way of checking the counter is to point it downwards to a non-polluted part of the ground, record the reading in counts/sec, this is called the background radiation.

Background radiation is as low as 4-8 counts at sea and around 30-40 in an area with clay or granite. Going up in the mountains might expose you to ~100 counts/sec from cosmic radiation. Now point it at the object you want to check, when the reading is less than 3x the background it can be considered non-polluted. That doesn't mean it's safe but at least there's less worry.

The biggest problem is these meters will not show you all radiation, usually only Gamma and Beta radiation while Alpha can be just as dangerous. Some sorts of radiation have a hard time passing through even a thin layer of moisture, that includes the skin of vegetables.

All in all, buying a Geiger counter is most likely a total waste of money and certainly a source of misinterpretation.

Use calibrated radiation sources (5, Informative)

goodmanj (234846) | more than 2 years ago | (#36214788)

"Point it at a smoke detector" won't work: the americium in smoke detectors emits alpha radiation, which can't penetrate the walls of the detector. There's no sense messing around here: if you want to do it, do it right. You will need a little bit of money and the ability to do math.

Buy a calibrated radiation source: you can buy them here [spectrumtechniques.com] , among other places. They're relatively cheap -- tens of dollars. Cs137 is very easy to get, but you also might want to get some Sr90, which is a pure beta emitter. These sealed disks contain such a tiny amount of radioactive material that the risk to health from them is negligible, and they can be mailed and used without a license. However, I do not know mailing them internationally is legal or wise.

(The same company will also sell you a lead container to hold your sources in, but I'll tell you from personal experience that quite a few gamma rays will go right through the container.)

Put the source in front of the detector, a short distance away. If your detector is working, it should start clicking/beeping like crazy. Calculate the count rate. By working out the geometry, looking up the properties of your source, and converting curies to counts per second (hey, nobody said this would be easy), you can work out the "efficiency" of the detector. Move the source farther from the detector: the counts should fall off as an inverse square law.

Now that the detector is calibrated, you can use that efficiency factor to calculate the radioactivity of an *unknown* source.

Important note: while these sources are generally considered safe, the radiation they emit will be *many* orders of magnitude more than any contamination in Japanese food products. You can look at this fact in two ways: either this shows that concerns about food safety are overblown, or suggests that the best way to protect yourself from unnecessary radiation is to not do this experiment.

If you don't have access to or don't want to buy calibrated radiation sources, you can buy yourself some "No Salt" salt substitute, which is food-grade potassium chloride. The naturally radioactive potassium-40 in it is easily detectable with a good Geiger counter: you can look up the natural abundance of 40K and do a little chemistry to figure out the number of curies in a carefully measured gram of KCl, and use it as a calibration standard.

Re:Use calibrated radiation sources (-1)

Anonymous Coward | more than 2 years ago | (#36215000)

the natural abundance of 40K

The natural abundance of 40K is highly variable, peaking in small shops filled with smelly men and overpriced plastic toys.

Re:Use calibrated radiation sources (1)

AmiMoJo (196126) | more than 2 years ago | (#36215116)

mportant note: while these sources are generally considered safe, the radiation they emit will be *many* orders of magnitude more than any contamination in Japanese food products.

And here-in lies the problem. Even if you calibrate your Geiger counter the readings will only be assured for much higher levels of radiation than you are likely to encounter. Instruments that can measure very low levels accurately are extremely expensive and require professional calibration. You couldn't just point one at your food either, it would need to be prepared (and destroyed) to get a good reading.

The good news is that I'm sure there are plenty of people with high end equipment checking food and soil for you. Even if you don't trust the government they can't just hide radiation, and there are plenty of academic institutions which are taking their own measurements.

where to get Geiger counters? (0)

Anonymous Coward | more than 2 years ago | (#36214790)

Try other countries. If the USA is backlogged, then try another country. Try Europe. Try Taiwan. Try Russia. Expand.

Local schools will have... (0)

Anonymous Coward | more than 2 years ago | (#36214810)

Test discs that are marked to what they should read on a counter. If you just want to verify it works an old school watch with a glow in the dark dial or hands will set it off.

Potassium-40 (0)

Anonymous Coward | more than 2 years ago | (#36214840)

The easiest way to test a geiger counter is to get a big bag of potassium chloride (found in water treatment salts, low or no sodium salts for diet purposes) . The radiation from the naturally present potassium-40 should be easily detectable with a decent counter.

No need to search for uranium glass or thorium containing lantern mantles.A sufficiently sensitive counter should also click randomly due to background radiation.

heres an idea... (0)

Anonymous Coward | more than 2 years ago | (#36214848)

send it to a geiger counter calibration house and get it calibrated.

really, this shit isnt hard.

this may help (0)

Anonymous Coward | more than 2 years ago | (#36214852)

http://xkcd.com/radiation/

Test samples. (2)

drolli (522659) | more than 2 years ago | (#36214854)

if you know somebody who organizes a lab course in physics, in a university you can ask if you can take the geiger counter there and compare it to their calibrated samples. Typically there is a box of sealed test samples (well locked away), which have well defined radiation doses in different gamma-ranges, so you can test the sensitivity. However, you will have to take an safety instruction to even touch the box. So if you know somebody there well, he may help you. He may even tell you how to calibrate the device correctly using that sample. Another way, which is less technically challenging and will not give you a quantitative calibration is to use one of the typical stones which radiate stronger. Refer to any standard textbook which these are in you region. Look e.g. for granite on wikipedia and follow to the original sources. However none of these means will provide you with any information about the sensitivity of the counter.

As for your friend trying to measure food: More than a quantitative comparison "this radiates stronger than that" will not be possible. The data will be problematically low for the prescribed doses if the counter has no good integrator/long term counter and is stable. Any quantitative measurement of contamination with isotopes is completely unrealistic outside the lab and with an inexperienced operator, especially if the device has no energy resolution. A simple workaround around the latter would be insert materials with different absorption coefficients into the path and compare the measurements, but i cant tell how well that works. Moreover 100-1000Bq/kg is not much. I doubt you manage to get more than a count rate of 1-10clicks per second from a sample of acceptable size. which means that in order to get a 10Percent resolution you may have to integrate over 100seconds or more. That means that the dark count rate should be acceptably stable.

If your friend does this to protect the own health, i recommend the following: don't do it. There are two possibilities: either the food in monitored professionally and marked correctly (which i believe is normally the case in Japan) or its not. If its monitored professionally then there will be no long-term contamination which is undetected. The effect of a spurious peak in one meal to ten or even hundred times of the allowed level wont kill you or have any adverse effects, and reliably i think you will be only able to detect starting from about 10-100 times of the allowed dose. If the food which is not monitored professionally *and* comes from within 50-100km around the reactor then don't eat it, if you have the choice, until the situation stabilized (that is, when any kind of containment, even by a simple plastic foil is reestablished and then after a few months, look at the ieae website). If you believe you must support the farmers there, then donate money, don't buy the food.

An non-reading can also provide you with a false sense of safety, and that is true for all uncontrolled foods. There is no way for a layman to establish safety of a food which comes from within the problematic range around the reactor.

My personal feeling is that *in Japan, which has high food quality in general* an inexperienced operator of a Geiger counter trying to measure his own food will have higher stress due to mis/unclear readings and the constant (lets remember, this may have to be done for 20years if you take it seriously) reminder of the danger just before eating. The adverse health effects of this and possible associated psychological effects (stress before eating) will outweigh the negative effects of getting a higher dose from time to time. If you take the 30min-1h per day which you need to check the food *seriously* for such low doses of radiation, then there are other thing you can do in this hour (go jogging, ride a bike etc.) which will help the body more to develop the immune system.

Don't bother. (2)

kombipom (1274672) | more than 2 years ago | (#36214884)

If I remember correctly the reported levels of contamination in the food and water supply in Japan were, even at their peek, in the order of a couple of 100Bq per kg. You need to put a sample in a counter or spectrometer for some time to be able to tell those levels from background. Pointing a GM tube at pieces of spinach to see if one is contaminated more than another is futile, all you are going to notice is variations in background. You can have fun finding all sorts of slightly radioactive things with a counter if you like but unless you are willing to spend >$10k on a portable gamma spectrometer which _might_ be able to distinguish tiny amounts of I-131 or Cs-137 from background you are not going to find anything in the food.

get the old Cold War stock models (0)

Anonymous Coward | more than 2 years ago | (#36214886)

try this:

http://cgi.ebay.com/CDV700-GEIGER-COUNTER-Radiation-Detector-NEW-OS-/350465234219

or

http://cgi.ebay.com/CDV700-GEIGER-COUNTER-Radiation-Detector-NEW-OS-/350465234219

It runs on D batteries.

Chose Wisely. (1)

logistic (717955) | more than 2 years ago | (#36214892)

There are lots of caveats as most of these meters are for detecting contamination rather than dose rate.

The CDV -700 has a pretty thick window so not super sensitive. They are all pretty old so you would be wise to check it carefully before using.

To reliably detect small amounts of radiation contaminating food you will need to spend a fair bit of money on something more sensitive that most of the survivalist supply stores:
http://www.ludlums.com/index.php?page=shop.product_details&flypage=flypage_ludlum.tpl&product_id=300&category_id=115&keyword=3_with&option=com_virtuemart&Itemid=95 [ludlums.com]
(they will also do calibration)

Eberline made very good instruments but I can't find them on the web as making them currently. They made also very good equivalent products. You may find a good used one of these.

Proper NIST traceable calibration may be worth your time the meters are generally calibrated for dose rate or energy from a standard Cesium-137 source Cobalt-60 is commonly used and they are both major fission products so they are good choices for the stated application):

One vendor near NY I found on web: http://biomedphysics.com/survey-meter-calibration-and-repair [biomedphysics.com]

The Reed College Reactor Facility might also do it. This will likely be the cheapest method (website quotes $50 per probe +shipping): http://reactor.reed.edu/metercal.html [reed.edu]

As others have mentioned most smoke detectors use Americium which is an alpha emitter. You need a very thin window and large surface area probe to detect this reliably. These don't make great test sources.

If you can find an older colman style lantern mantle made of thorium (the newer "safer" ones do NOT have thorium) they make great test sources and will set off most Geiger counters and are really useful as you should check to make sure it's working with every use. The probes are delicate, the batteries die etc so if it's important check every time. Keep them in a plastic bag so they don't contaminate your detector!

Good Luck!

United Nuclear (1)

mrmeval (662166) | more than 2 years ago | (#36214904)

http://unitednuclear.com/index.php?main_page=index&cPath=2_5 [unitednuclear.com]

All Isotopes are sold by the microcurie (uCi)
( 1 microcurie = 2.22 x 10E6 disintegrations / minute = 2,220,000 cpm )

Normal sources are + or - 20% pf stated value.
For calibrated sources, add $120.00 and source will be + or - 5% of stated value and will include a calibration certificate.
Calibration is only available for gamma sources.

safecast.org (1)

gnaac (705946) | more than 2 years ago | (#36214922)

So this doesn't specifically address your question about geiger counter testing, but if you're interested in the radiation levels in japan, and an attempt to crowdsource radiation collection, check out http://www.safecast.org/ [safecast.org] Also, I recall reading somewhere that they were working with some group to create a DIY geiger counter. Might include some testing info as well.

No (1)

Orgasmatron (8103) | more than 2 years ago | (#36214928)

You can't calibrate it yourself. Or, if you could, you wouldn't be asking here. You need special equipment.

Look here. http://www.radmeters4u.com/calibrate.htm [radmeters4u.com]

Simple Test (0)

Anonymous Coward | more than 2 years ago | (#36214936)

Test it compared to a known source. The Geiger counter should come with a test source of known activity, which will allow you to calibrate it. Aside from that, go online and find acceptable levels of radioactivity in foods to determine where your threshold should be. Young children and the elderly should have their acceptable thresholds adjusted, but you should be safe in staying with the average.

The reviews are a bit mixed but... (1)

kEnder242 (262421) | more than 2 years ago | (#36214940)

http://www.amazon.com/Images-SI-Inc-Uranium-Ore/dp/B000796XXM

I call bullshit (0)

Anonymous Coward | more than 2 years ago | (#36214984)

Guess what, I live in Japan too. Geiger counters are easy to get.

go to Akihabara station, go out the exit with Yodobashi camera, and turn left. Walk across to where the McDonalds is, and go down the stairs to the place that sells electronics stuff (Mainly used PCs and unlocked mobile phones). They have new Geiger counters - as do many places in Akihabara.

Then again, you don't really need it, since the government, scientific agencies, educational institutions, and even other hobbiests are measuring and posting the numbers online all the time.

There is also the issue of knowing what you are measuring and what it means. Unless she lives reasonably near to Fukushima, the levels in Tokyo and below are at average.

Use potassium (0)

Anonymous Coward | more than 2 years ago | (#36214990)

Potassium 40 is a beta emitter. Buy some kg of a potassium compound (KCl, KNO3, etc. Plenty of fertilizers are made up of potassium salts), estimate the total amount of K present in your sample, and from this chart [bnl.gov] you can easily estimate the total activity of your sample. If you are lazy, the 0.0117% of your potassium is radioactive. Estimating the amount of radiations emitted in a second and how to estimate the expected number of counts hitting your Geiger detector is a trivial exercise, that you should be capable of performing, since you want to succesfully calibrate and use a Geiger counter.

Don't worry - be healthy. (1)

Anonymous Coward | more than 2 years ago | (#36215002)

You can purchase an exempt quantity Cs-137 check source from several vendors, Isotope Products, Inc is one. Probably run around a hundred bucks. Exempt quantity is the amount below which a license is not required for possession. for Cs-137 it's 10 uCi, which is strong enough to get a decent reading on a GM instrument. What you really should do is send the instrument to a calibration facility like Ludlum Instruments in TX and have it calibrated to a NIST traceable source. Once you have a calibrated instrument, you need to know what you're looking for. If you're testing food, you need a thin window GM, capable of reading in counts per minute and you want to see 100 cpm above background, which is a common release limit in the nuclear industry based on a 10% instrument efficiency. If your geiger counter doesn't have a thin window detector, it's probably not sensitive enough to detect minimally contaminated foods. I'm sorry to say that most of the detectors available to the public are useless in detecting the levels of contamination you'll be looking for. I think your best bet is to wash your food thoroughly and trust that the government of Japan is monitoring the levels carefully. Try not to panic. The stress of worry is much more harmful than any radiation exposure you're likely to receive.

Plutonium (1)

phagstrom (451510) | more than 2 years ago | (#36215008)

Plutonium should be available in every corner drugstore by now....if not....talk to some Libyens....they may want to trade with some used pinball machine parts.

Though I know there is a lot of concern... (1)

Tsian (70839) | more than 2 years ago | (#36215042)

As a resident of Japan, it strikes me as far more productive to donate the money I would use to buy a Geiger counter to disaster relief aimed at helping those more directly affected by the quake and tsunami. The government has been strictly monitoring levels in food and has been quite quick to prevent shipments of any food which might present even a small risk.

Banana's (1)

Neil Boekend (1854906) | more than 2 years ago | (#36215118)

Use this chart [xkcd.com] and a bushel of bananas.

Calibration (1)

MichaelSmith (789609) | more than 2 years ago | (#36215154)

You get a caesium source and measure the radiation level with a known good instrument, and the instrument you want to calibrate. The physics department of any good university should be able to do this. Its a standard prac exercise.

Hire a professional (1)

predatormc (1791430) | more than 2 years ago | (#36215226)

The results you are going to get testing foodstuffs with a Gieger-Muller are going to be poor, almost certainly the levels of radiation in food are so low that the statistical fluctuations in the background count rate will render your results useless. You are definitely going to have to invest in some lead shielding to remove some of the background count to determine anything useful from your data. To do this properly I would recommend a more sensitive detector such as HPGe or an inorganic scintillator to actually determine the radioactive source content for proper analysis of the risks. I regret that someone is profiting horribly from the sale of GM tubes to people who are naturally scared for their health but have no idea how to use them and most importantly how to interpret the data they produce. Alpha particle emitters in foodstuffs are the most dangerous (tissue weighting factor x20 compared to gamma) but they will not be detected with a GM tube unless you place the source inside the tube itself. GM tubes with a thin window are quite good at detecting beta-particle emitters which are also harmful but it will be difficult to tell what source is actually emitting the radiation and the energy of the beta particles. The efficiency of a GM tube isn't that great with gamma radiation because it's so penetrating and gas naturally isn't very dense. As mentioned already calibration with a Cs-137 gamma source and a Sr-90 beta source by a should be carried out for a GM tube regularly, the efficiency of the detector can be calculated using some simple geometry calculations.

Try this (0)

Anonymous Coward | more than 2 years ago | (#36215244)

http://www.ehow.com/how_6786889_calibrate-geiger-counter.html

and im guessing you have something like this to send there.
http://www.coleparmer.com/catalog/product_view.asp?sku=0899050

Spend the big money ... (0)

Anonymous Coward | more than 2 years ago | (#36215260)

... on getting proper calibration equipment.

Recoup the expenditure by playing on the paranoia of others that they should be suspicious of the calibration of their own Geiger counters.

FiestaWare (0)

Anonymous Coward | more than 2 years ago | (#36215320)

Red/Orange FiestaWare from the 1930s

http://www.orau.org/ptp/collection/consumer%20products/fiesta.htm

Fun with Geiger Counters (1)

Registered Coward v2 (447531) | more than 2 years ago | (#36215348)

1. Set the scale on as low as possible and watch people freak when the needle pegs ...

2. When responding to a reported incident, set the scale as high as possible so people feel safe and don't panic since all they hear is a slow tick...tick...

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