Radiation detection

[rat4spd]

You're welcome, but I didn't necessarily put the description there for you. It was more to give the idea of gamma energy in as simple a way as I could.
Ok, now I understand what you are getting at: The fire analogy is showing the parallel between an atomic bomb blast and a fire.

There is a pretty close relationship between the two. The heat and fire are the initial blast, and the smoke and ash are the fallout that is left over and lingers...

Neither of the types of CD survey meter were intended to indicate the initial blast (heat and flame). Both were made for registering the fallout... the ionization chamber meter was intended to give you a measurement that allows relatively safe travel in a contaminated area, and the GM tube meter was intended to help in keeping the shelter clear of fallout residue that might be tracked in, or ride in on clothes.

However, the fire analogy has nothing to do with the measuring capabilities of a survey meter using an ionization chamber vs a survey meter using a GM tube. The difference is purely one of quantity. They each treat the energies of all gamma photons as being the same, but shows a measurement of the flux, or number of photons per second.

-Chuck

Really Chuck, I'm just joking with anyway, and I haven't really been following the discussion on meters, but if I had one to pick, I'd pick a frisker of one of many variants.

Reason being, I'm not as concerned about mR/hr as I am counts per minute. A frisker will give you good all purpose beta/gamma, has good sensitivity, and since radon daughters are beta emitters, you can have a good time in the winter during temperature inversions.

 

[stumps]

I presume by "frisker" you are referring to just about any G-M tube counter that has its G-M tube at the end of a cable, and has a mica beta window?

The usual radon detector setup is an ionization chamber that lets the room air into the chamber, and looks for an electrostatic charge change due to the beta from the radon daughters. There are some pretty reasonably priced [ <$150 ] radon detectors on the market. I haven't, however seen any count variation on any of my G-M counters. I remember seeing a film-clip of a uranium miner blowing at a G-M tube, and getting 50 or 100 mr/h reading from all of the radon in his lungs.... good thing he was a smoker

-Chuck

 

[rat4spd]

Your GM detector isn't reading the radon. Your Radon daughters of lead, bismuth and polonium doing a manner of beta decays like you say is what you'd read. In Idaho for instance, which has a phenomenal amount of Radon in the winter, the abundance of static electricity on your knees and elbows attracts the radon, of course with its positive charge. So when you would egress spaces and do our personnel frisk, we would be as though we were "crapped up." A simple sheet of paper will block a good bit of the counts and give firm evidence of radon.

After our clothes would be stripped, they'd spend the rest of the day decaying to less than, and we'd get them back.

So I wouldn't use the frisker to detect radon, but detect radon by proxy. You could also give your furnace filter a good check. I'm sure that'd be interesting. And mind you, I'm not implying that waving the probe in the air will detect the daughters. They need to be concentrated on your knees ans such or in a paper air sample.

Then there's the americium 241 plug in your smoke detectors which still blows my mind how hot it is.

http://www.civildefensemuseum.com/southrad/eberline-e140.html
I spent a lot of time with this, although using a pancake probe for personnel decon, and a tungsten shielded probe for surveys.

 

[stumps]

I am aware that a GM detector doesn't read the alpha decay of Rn222. I have an Eberline alpha counter that can, but I haven't noticed any reading in my environment, so I might not have all that much radon. Because at any given point in time a certain percentage of the Rn222 is alpha decaying, there are always daughters (Po218, Pb214 and At218 ) present in any radon gas....and as a result, plenty of alpha and beta particles... and yes, I had to look that up in my nuclide chart. I don't spend too much time thinking about this stuff anymore.

Alpha counters are fun to play with. You can get a different reading depending on whether the source is above the counter, or below... the alpha particles apparently like to rise in our atmosphere, so the count is higher if the probe is above the source, than it is if it is below the source. They also give a real easy demonstration on how easy it is to stop alpha... a piece of paper does the job completely.

Eberline is probably the best of the available surplus counters. I have several of their instruments, including one of their universal Rate scalers... RASCAL. It is a shame that its LCD display has gone wonky and became all blotchy. I wish I could get a new LCD for a reasonable price... wouldn't mind finding a manual too.

-Chuck

 

[rat4spd]

I have an Eberline alpha counter that can, but I haven't noticed any reading in my environment, so I might not have all that much radon.

I don't think you would anyway. When we took air samples, it was about 1 cubic meter, and even then sometimes there wasn't much to detect. Sometimes it was a whopper when there were temp inversions, detecting any measurable activity from only the air surrounding the probe wouldn't get anything, except maybe an extra CPM background.

Eberline is probably the best of the available surplus counters. I have several of their instruments, including one of their universal Rate scalers... RASCAL. It is a shame that its LCD display has gone wonky and became all blotchy. I wish I could get a new LCD for a reasonable price... wouldn't mind finding a manual too.

I don't have any experience with meters outside of the Navy. Even then, they were dated, although I have heard they have since changed. I don't have the curiousity to play with them though as I was so paranoid after I got out due to an increased awareness of how much radioactive material there really was in our lives.

 

[stumps]

When I tried the alpha counter, I used the television screen as a "concentrator", but still no sign of the daughters. We are in a fairly high radon area, because of the nearness of the granite to the surface in our geology... but not as bad as some areas.

Smoke detectors are a favorite source among the counter nuts. Being as they are used in an ionization chamber, they put out lots of beta. I too am surprised that they are allowed out into the population... yea, not just allowed, but mandated! Coleman lantern mantles used to be a hot source of alpha, but they changed the formulation.

I don't worry too much about our natural radioactive load, but some of the artificial loads we are exposed to bother me quite a bit. Like the time they shot me up with Technetium-99m when checking out my back.... The technician didn't even ask me if it was ok until after she had done the deed... I walk in expecting an x-ray, and I walk out a potent gamma source! I have never seen so much gamma activity... and most of it coming from my bladder. When I made the count after I came home, I was pinning 50mr/hr... [PDR27's switch to a smaller GM tube with heavier steel walls that couldn't see 140Kev on the 500mr/hr scale.] I started drinking water heavily to wash the stuff out. Yes, I know that Tc-99m has a 6 hour half life, and puts out 140kev photons... relatively weak stuff... but my dose amounted to probably 500 chest x-rays, all because my doctor wanted to check for arthritis in my back... I am also less excited by the idea that it all decayed to Tc-99 which is a beta emitter... just what I need in my body.... after years of trying to keep my dose down they did that to me.

Speaking of artificial loads, I remember when China blew off their first open air bomb in the '70s. The news was silent on the issue, but my G-M counters went nuts after rain storms for several weeks following the blast... love that Iodine - 131!

-Chuck

 

[rat4spd]

I don't worry too much about our natural radioactive load, but some of the artificial loads we are exposed to bother me quite a bit. Like the time they shot me up with Technetium-99m when checking out my back.... The technician didn't even ask me if it was ok until after she had done the deed... I walk in expecting an x-ray, and I walk out a potent gamma source! I have never seen so much gamma activity... and most of it coming from my bladder. When I made the count after I came home, I was pinning 50mr/hr... [PDR27's switch to a smaller GM tube with heavier steel walls that couldn't see 140Kev on the 500mr/hr scale.] I started drinking water heavily to wash the stuff out
Speaking of artificial loads, I remember when China blew off their first open air bomb in the '70s. The news was silent on the issue, but my G-M counters went nuts after rain storms for several weeks following the blast... love that Iodine - 131!

-Chuck

Funny you mention that. I remember a guy that had something similar....don't remember the isotope, but he of course had his dosimetry stripped, and he had a designated toilet to urinate in, after which we would have to survey.......

 

[AN/ARC186]

Anyone have a PDR-27/S they want to sell?

So back to my original question.......

 

[dependable]

Well I just got a cdv700 off e-bay. Paid more for one that was practically unused and recently calibrated (12/09) . It came with books and a couple of test samples, old glass marbles with a bit of uranium for color, and a net ''mantle'' for a Coleman white gas camping lantern. That made the unit light up compared to a few clicks from the test spot on side of meter or the uranium colored marbles. House, shop and trucks all tested ok, but I don't have a lot of made in china tools.

 

[donalloy1]

wowww! u guys are deep....

 

[3dAngus]

OK, now has anyone ever tested their MV with one of these radiation meters and ever found a trickle of radiation, either on the MV, the gauges, or tires? It would be interesting to know and test. If so, I would like to get a meter myself. Heck, I might even have one already stored around here somewhere. Better check. I feel like playing!

 

[EMD567]

Since my dad worked in the nuclear industry, I already know I am crapped up beyond help. All I remember him saying is that everybody that have seen the blue light of an unshielded nuclear reaction are dead.

 

[islandguydon]

PM sent. This will answer any and all of your questions on radiation detection.

 

[glcaines]

I work with radioactive materials daily and have access to all kinds of radiation survey instruments. Anyone in the North Georgia area that ever wants to get their MV and especially their gauges tested, please send me a PM. I will also bring instruments to the 2012 Georgia Rally if anyone wants to check their MVs.