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 2.GQ Geiger Muller Counter
 Does GMC 320 detects radiation by radon gas
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cooper

4 Posts

Posted - 11/06/2015 :  23:00:23  Show Profile  Reply with Quote
I bought one for checking radiation at home and I heard that radon gas is one major factor.

Does GMC 320 detects the radiation created by radon gas?
Thanks for your reply.

Paul
Reply #1

nico.v.44

France
4 Posts

Posted - 11/07/2015 :  14:20:35  Show Profile  Reply with Quote
Yes : h**p://sciencedemonstrations.fas.harvard.edu/presentations/radons-progeny-decay

and : h**ps://www.youtube.com/watch?v=wnOIH_UQRQ0

Nicolas
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Reply #2

cooper

4 Posts

Posted - 11/07/2015 :  16:48:40  Show Profile  Reply with Quote
Thanks for your reply but I cannot understand the language on video.
Once again thanks for your input.
The page use Mev and I use uSv/h I got something from 0.03-0.1 which I believe still safe.

Paul
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Reply #3

Distelzombie

Germany
202 Posts

Posted - 11/12/2015 :  02:55:41  Show Profile  Reply with Quote
The guy in the video basically hang an inflated balloon 40min (Don't leave it longer than 40min. the static charge will wear off or something.) in the area he wanted to measure radon in. (actually radon gas is extremely heavy so put the balloon on the floor. I did not do that in my testings down there ...) He used a microfiber cleaning towel to charge the balloon electrical. That is necessary to attract radon atoms.
After this 40min he measured the balloon as seen in the video. I would suggest putting the balloon under the GMC because the tube is otherwise shielded by the board an casing. (Unscrew the casing for best measurement conditions)

I actually did that today and I got a reading of about 25-30 CPM over background.
I'll now try to enhance my balloon-charging-technic and then hanging it directly underneath a (probably) 78k CPM pitchblend. ("Probably" because maximum number of cpm of the gmc is 65,5k)
I'll see what that does...
... aaand it does ~105cpm above background. Now let's see if it decreases in the next couple hours to nothing.
Radon gas emits only alpha radiation and we can't measure it. (with our gmc's) But we can measure the daughter isotopes and they have a half life of around 26.8 min. So, we are only indirectly measureing radon.
Now roughly 1h later my gmc measures just 30cpm over bg. I did not move it. I think I'll try that in the basement. It will accumulate down there.

I just found this document describing different techniques of measuring, if something is still unclear: h**p://media.cns-snc.ca/uploads/teachers/Walkiewicz_p1_p2.pdf

Interesting! A balloon in the basement will produce 930CPM over background! That is 5.5ySv/h!
It's 2 am now (Germany), let's see what it reads in ...
One hour: 450cpm
Two hours: 200cpm
Three hours: 54cpm

Please note that I have no idea if that is a save amount or not! I think that you can only measure the sheer presence of Radon gas, but not the amount using this technique. But if the balloon from your bedroom produces 930CPM I would get worried. :)

But now that I've measured my freshly ventilated living room with an balloon charged by my hair (best way to charge him), I would say that any reading over 100CPM above background, with our GMC!, should be considered "unfresh air".

GMC-300E+ V4.20 with sbt-11a alpha tube

My statements are "stuff-a-hobbyist-says" and not in any way professional.

Edited by - Distelzombie on 11/14/2015 15:57:41
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Reply #4

Distelzombie

Germany
202 Posts

Posted - 11/14/2015 :  16:00:29  Show Profile  Reply with Quote
I suppose that now that I've updated my post about ten times over the past ten days, I should make a new just to update the messages the TE gets.

*boom*

GMC-300E+ V4.20 with sbt-11a alpha tube

My statements are "stuff-a-hobbyist-says" and not in any way professional.

Edited by - Distelzombie on 11/14/2015 16:02:29
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Reply #5

ZLM

1178 Posts

Posted - 11/17/2015 :  22:34:32  Show Profile  Reply with Quote
This is very interesting experiment. I will try this later.
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Reply #6

NRFneversail

USA
22 Posts

Posted - 11/20/2015 :  18:46:24  Show Profile  Reply with Quote
I used to work at Naval Reactors here in Idaho with radioactive materials/nuclear fuel and survey meters. Though I was not a qualified Rad-Con Tech, I was qualified to carry out limited Rad-Con surveys. As I recall with Radon, it emits an Alpha particle as a result of radioactive decay and Alpha can be stopped with a sheet of paper or your skin for example but can still penetrate soft tissue like in your eyes and lungs. When we were in situations there may be Alpha and Beta particle exposure, we were required to wear a plastic face shield. This Alpha however was emitted from an item with fixed and or loose contamination and was not the same as being in a room with Radon Gas. Some low speed Beta can also be stopped by these things but high speed Beta can penetrate them.

I guess I'm puzzled how Alpha particles could be penetrating a plastic case and a GM tube I assume is w/o a Mylar window like found in Pan-Cake probes used for detecting Alpha particles. I could possibly see high speed Beta particles detected by an unshielded glass GM tube along with X and Gama but if this guy in the video is detecting high speed Beta, I'm thinking there may be bigger problems than Radon. It has been a lot of years since I worked with radiation and contamination and could be missing the mark but maybe an old HP or Rad-Con Tech could clear this up. I do recall though wearing polyester to work was taking a chance you would lose your jeans and or shirt. The knees and elbow areas in particular with static electricity even had me trade one or the other in for a pair of paper coveralls. Rad-Con had to prove it was radon that was detected on your person while frisking out of a Radiological Controlled Area (RCA) before getting your pants back for example. I can remember times the Radon activity was above our work area air survey limits but outside the building was worse so we frisked out of the RCA and sat in the lunch room until the indoor work area was acceptable again or the outside was lower so allowed ventilating the inside to the out through special filters. The balloon thing has me curious so maybe one day I will try my Eberline 520 with a Pan-Cake probe to check for any results. If there is any radon on the static surface of the balloon, it should detect it and then can reasonably assume Radon by shielding the probe with a piece of paper to get an immediate CPM decrease. It's half life should also decrease through time confirmed with a series of survey readings.

Edited by - NRFneversail on 11/21/2015 09:40:23
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Reply #7

Distelzombie

Germany
202 Posts

Posted - 11/21/2015 :  03:01:15  Show Profile  Reply with Quote
Hi NRFneversail. You are totally right to question this. This tube has no Mylar window.
As I said in my fairly big post up there: our tube cannot measure alpha radiation and since this guy has the same device, he can't either.
The ions that we measure are from the radon decay chain. Radon itself has a half life of 3.8 days but the daughter ions have half life's of about 28min and less. If it were just for radon we wouldn't see a big change in the reading in under 2 days.

Polonium-218, lead-214, bismuth-214 and then polonium-214 are the main source of the radiation that we measure in this experiment, with lead being the longest living.



Yesterday I measured (1200CPM) americium-241 from an new smoke detector. (Source has 33kBq) I unscrewed the casing and put the source directly onto the tube. There was only a 200CPM decrease after I shielded it with one layer of aluminum foil.
After this experiment we can be sure that the M4011 tube does not measure a meaningful amount of alpha radiation - if at all since the foil could have blocked low energy beta radiation.

GMC-300E+ V4.20 with sbt-11a alpha tube

My statements are "stuff-a-hobbyist-says" and not in any way professional.

Edited by - Distelzombie on 11/21/2015 03:03:32
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Reply #8

NRFneversail

USA
22 Posts

Posted - 11/21/2015 :  10:27:01  Show Profile  Reply with Quote
I'm glad you brought up the Radon daughter Ions because when Rad-Con took our pants for example because the alarm point in frisking above background was exceeded, the testing they did was to look for this 28 minute and less half life. If it was proven and took about an hour for the whole process, you got your pants back, if still Hot or Crapped Up as we called it, you got your pants back but with a hole where the activity was found. That part you were not taking home with you and you would most likely end up in a critique with people wanting to know how you got crapped up (contaminated). I do recall where the clothing was checked was inside a neat stack of lead bricks to eliminate cosmic and other background activity. One practice was if your jeans had a hot knee, Rad-Con would place Duct tape over it so to contain it before bagging the jeans up and taking them to the Counter. They would also record the time detected and how many CPM above background. Working with and controlling contamination was one of the most fascinating things I have ever done.

I remember as a Rad-Worker and Fuel Handler, I think it was every two years I had to have a Whole Body Count. You stripped yourself of everything, took a shower, got in your paper hospital gown and shoes, and entered a steel, lead sheet, and copper sheet surrounded room. I have no idea what the thickness of each were to figure the TVL's but it looked quite sufficient to me to eliminate any external activity. In there you would lay on a very comfortable bed and the HP or Rad-Con Tech would place a couple of very sensitive large probes near your throte and abdomen. At that point they left and you could fall asleep or stare at the room. This test was to see if we had ingested any work related radioactive isotopes.

I'm glad to see I had not forgotten too much about the energy of Alpha and Beta particles. I will also vouch that Time, Distance, and Shielding can be very effective in reducing radiation exposure. I worked under maybe the most stringent Rad Controls in the world but I still respect unstable Atoms.

Edited by - NRFneversail on 11/21/2015 10:34:32
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Reply #9

toplard

United Kingdom
2 Posts

Posted - 11/06/2017 :  13:10:28  Show Profile  Reply with Quote
Wow, so this is why passive smoking is disproportionately bad for us? Just guessing badly - Radon progeny easily attach to smoke aerosols?

Robin Smith
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Reply #10

Distelzombie

Germany
202 Posts

Posted - 12/20/2017 :  00:18:28  Show Profile  Reply with Quote
I don't think that is the main reason. I never heard about that.
Also, Radon is heavy. It will accumulate on the ground and probably won't reach the smoke of a cigarette.

GMC-300E+ V4.20 with sbt-11a alpha tube

My statements are "stuff-a-hobbyist-says" and not in any way professional.
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