pwhole
Well-known member
Aha, thanks for that Bob. So it's even worse than I remembered!
β/γ radiation in caves and mines
- Thread starter CJ
- Start date
Bob Mehew
Well-known member
Sorry to go back to basics, but is the level of beta & gamma radiation being measured by CJ due to radon or due to the surrounding rock? That could be tested by taking the meter down in a sealed poly bag (preferably one used for vacuum storing clothes and such like so it is less porous), taking a reading and then opening the device up and waiting a few minutes for the cave air to properly circulate through the meter.
CJ
Member
For the initial test, the meter was taken down in a sealed pelicase, turned on and then shortly closed again. The reading shown in the original post was when the meter was out of the case, but if I recall correctly, there was not a huge difference in the readings when the meter was in/out of the pelicase. Next time I'm there I will aim to be more rigorous in my methodology as I hadn't considered this.
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BetterGeiger
New member
Hi all,
I'm the "Better Geiger" guy, creator of the product CJ was using down there ( www.bettergeiger.com ). We had more communication than the average customer because of some shipping complications (some combination of USPS/covid/brexit has caused a lot of trouble with my shipments to the UK, but that's a different topic).
From a quick scan through this thread I wanted to add two things -
1. As CJ mentioned at the start the detector is sensitive to beta, but the efficiency is very low so in practice unless you are very close to a fairly strong beta emitter the dose value you read will generally just be from gamma. So extra beta shielding under normal circumstances is not needed, but if you are measuring a specific object you could put a little aluminum between and check how that affects the count rate to see how much of the count rate is coming from beta.
2. As someone mentioned, alphas are 20x more damaging to cells than X-ray/gamma/beta. That's only part of the story, though, external alpha will generally be of little to no harm because the energy is deposited in your skin which is very insensitive to radiation (in fact it will usually not even reach there, as clothing will block alpha). However, when inhaled or ingested an alpha emitter can deposit energy directly into lungs and other organs, that's where the 20x factor comes into place. There are correction factors for whole-body exposure (usually relevant to X-ray/gamma) vs. if an exposure is entirely to one specific organ (like skin or eyes, or in medical situations when you get an X-ray to a specific body part, etc.). The story gets complicated quickly.
For you all though, as I think you are all well aware, radon is the main concern most of the time, which is of course an issue because it is gaseous and being inhaled.
I gave a lot of more general information over here on reddit recently, I'm drafting more thorough general info for my web site, feel free to take a look although I forgot to talk about radon there because that post was aimed specifically at the prepping community which was an unexpectedly large part of my customer base:
If you have any questions for me feel free to ask, but if I forget to check back here then send them via my web site.
Stay safe down there!
I'm the "Better Geiger" guy, creator of the product CJ was using down there ( www.bettergeiger.com ). We had more communication than the average customer because of some shipping complications (some combination of USPS/covid/brexit has caused a lot of trouble with my shipments to the UK, but that's a different topic).
From a quick scan through this thread I wanted to add two things -
1. As CJ mentioned at the start the detector is sensitive to beta, but the efficiency is very low so in practice unless you are very close to a fairly strong beta emitter the dose value you read will generally just be from gamma. So extra beta shielding under normal circumstances is not needed, but if you are measuring a specific object you could put a little aluminum between and check how that affects the count rate to see how much of the count rate is coming from beta.
2. As someone mentioned, alphas are 20x more damaging to cells than X-ray/gamma/beta. That's only part of the story, though, external alpha will generally be of little to no harm because the energy is deposited in your skin which is very insensitive to radiation (in fact it will usually not even reach there, as clothing will block alpha). However, when inhaled or ingested an alpha emitter can deposit energy directly into lungs and other organs, that's where the 20x factor comes into place. There are correction factors for whole-body exposure (usually relevant to X-ray/gamma) vs. if an exposure is entirely to one specific organ (like skin or eyes, or in medical situations when you get an X-ray to a specific body part, etc.). The story gets complicated quickly.
For you all though, as I think you are all well aware, radon is the main concern most of the time, which is of course an issue because it is gaseous and being inhaled.
I gave a lot of more general information over here on reddit recently, I'm drafting more thorough general info for my web site, feel free to take a look although I forgot to talk about radon there because that post was aimed specifically at the prepping community which was an unexpectedly large part of my customer base:
If you have any questions for me feel free to ask, but if I forget to check back here then send them via my web site.
Stay safe down there!
ZombieCake
Well-known member
I understand that alpha is rather bad if alpha emitters get inside you. Externally I think is effectively blocked by skin / a few sheets of paper etc. but if it gets inside then it's like a high density pinball bashing with your cells. I think the worst example in recent times was polonium put in a dissident's tea. Nasty stuff.
I've a few bits of clear uranium glass. They used uranium oxide to colour the glass that typical yellow-green / green colour. A UV light will cause it to glow while the UV is shined on it so that's a pointer if you don't have a geiger counter.
I've a few bits of clear uranium glass. They used uranium oxide to colour the glass that typical yellow-green / green colour. A UV light will cause it to glow while the UV is shined on it so that's a pointer if you don't have a geiger counter.
Bob Mehew
Well-known member
Looking at Better Geiger's web site, I see he comments that the device won't respond to radon. So it seems you are just measuring the gamma radiation levels. So the next question is "Do you see any variation between locations and at a given location at different times?" My expectation is possibly yes between different caves though less likely for diffrent locations within a given cave and no for different times. As a contrast, it would also be interesting to see how the radiation level varies in your dwelling place over a number of days. Measure it upstairs and just switch it on every so often, leave it for say 10 minutes (precisely) and take the cumulative measured value and divide it by the time left on (10 minutes or what ever). My expectation is it should not vary signficantly, but the data will give you a handle on the precision of the measurement.
Speleofish
Active member
Thanks BetterGeiger, that's a really useful summary.
droid
Active member
I know someone who couldn't do Giants in summer because they'd set off the alarms going into a radiologically sensitive area...
Boy Engineer
Active member
“Prepping community”. Yet another search to learn something new. What’s wrong with hiding behind a door? Just hope I can unscrew one in time, but there’s nothing like a deadline to concentrate the mind.
