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 2.GQ Geiger Muller Counter
 GMC 500+ and Granite Countertops
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ellie

USA
7 Posts

Posted - 05/25/2021 :  16:26:27  Show Profile  Reply with Quote
Is this meter appropriate for checking radiation in granite countertops? By either laying directly on the countertop or checking the air in the kitchen? Would this meter be effective in this way?

Thank you.
Reply #1

ullix

Germany
602 Posts

Posted - 05/25/2021 :  23:43:00  Show Profile  Reply with Quote
Certainly. What you'll find will of course depend on the granite that you have. Some material will show a higher, some a lower count rate. It may even be different across your countertop. But it will be low. I have a sample of granite, which gave double the background rate. Noticeable but still low.

The radioactivity will come from traces of the decay chains of some heavy metals (https://en.wikipedia.org/wiki/Decay_chain ), plus perhaps the omnipresent Potassium.

Nothing to worry about; it just demonstrates how sensitive a rather cheap device such as these Geiger counters are.
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Reply #2

ellie

USA
7 Posts

Posted - 05/26/2021 :  05:42:06  Show Profile  Reply with Quote
From my research it appears this model does not detect Alpha, is that correct? Isn't radon from granite Alpha? I also have a radon mitigation system in our basement from the area we live in having radon in the ground. I would assume the mitigation system is taking radon from the ground area only and not factoring the air in my house into my a couple floors up. I really wanted to check my main living space for radon since I have so much granite as well as a large rock/crystal collection. Am I correct that this meter is not going to work in the way I am hoping?
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Reply #3

ullix

Germany
602 Posts

Posted - 05/27/2021 :  02:45:40  Show Profile  Reply with Quote
You are right that the tubes in a GMC500 cannot detect alpha. But that is not necessary to detect " radiation in granite countertops", which your question was.

Check the decay chains in the Wiki link I had given. All decay chains have beta emission, which can be detected with gmc500, and almost everywhere - not shown on Wikipedia - you have gamma emission. You can see it here: https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html . Look up Uranium 238 and gamma and be prepared for some heavy lifting!

Actually, if you had a counter with a tube with "Mica window" which allowed detection of alpha, you'd have a hard time distinguishing from the counts resulting from alpha, and those from beta and gamma. Most counts will probably come from the latter.

Considering your granite, rock and crystal, I am curious for your results. You will probably need good patience to even get a decent statistic.

Regarding Radon I suggest to read this thread http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=9557 . Radon is not trivial to measure. Let's see if Damien succeeds with his new charcoal goodies.

I am sure, you won't see any even remotely dangerous things. And if this current counter does not tell you otherwise, an expensive counter with "pancake tube with Mica window" will only be a more expensive gadget telling you the same thing.

Edited by - ullix on 05/27/2021 02:46:59
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Reply #4

Damien68

France
516 Posts

Posted - 05/27/2021 :  05:02:07  Show Profile  Reply with Quote
I made two attempts at measurements which gave nothing. absolutely no peaks neither on the side of the Hepa filter nor on the side of the charcoal.
there is one thing: it is that I changed my vacuum cleaner bag, in the new one there is no more dust, this may be why the radon is no longer fixed, it may not be the HEPA filter which retains the radon but it can be the dust retained by the HEPA filter which fixes the radon.
This winter, I ventilate my house less, and radon infiltration is not constant, which is another possible reason.
but I have had several positive results before. I will redo the tests later. but the principle (using hoover to test for radon) seems to be able to work.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 05/27/2021 05:10:17
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Reply #5

ullix

Germany
602 Posts

Posted - 05/27/2021 :  06:06:15  Show Profile  Reply with Quote
@Damien: interesting. But I do not expect that HEPA filters by themselves would capture anything. Zero, nothing, nada, nüscht! If anything does it, it is the charcoal, as already good old Rutherford knew (I quoted him in the other post).

So, it ain't easy, even you are well versed in using Geiger counters.
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Reply #6

ullix

Germany
602 Posts

Posted - 05/28/2021 :  01:40:12  Show Profile  Reply with Quote
@ellie: I ran a few quick tests on Granite. "Quick" means at least 1 hour of measurements per condition!

I used an GMC300E+, which has the same or at least similar tube as the GMC500+ has as its main tube. The logging was done with my software GeigerLog ( https://sourceforge.net/projects/geigerlog/ )



The tests were run with 2 conditions: one had the counter's backplate removed, the other had it on. For both I tested the background, as well as the counter on Granite.

You see a background of CPM=16. When on Granite with the backplate on, counts increase to CPM=18. With the backplate off, counts increase to CPM=25.

Granite's radioactivity is detectable. Although barely so.

The count difference between with and without backplate suggests that the Granite is emitting some beta radiation, which is mostly absorbed in the thin plastic of the counter's backplate and thus does not reach the tube when the backplate is on.

For more on this, see my "Potty Training" ( https://sourceforge.net/projects/geigerlog/files/Articles/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download ).

The radiation level of Granite, or any other building material, is just very low. You'll find more in garden fertilizer due to its content of Potassium, again, see Potty Training.



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