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Discussion Starter · #1 ·
Hello to all. I ve been lurking for some time and decided to join in light of the lessons to be learned from Japan.

For the past 10 years I lived in Mexico -- I came back to the USA 14 months ago because of security considerations there. Currently I am planning another trip South, somewhere in South America.

For a number of reasons my life in Mexico was a lot different than here-- one always kept spare potable water, a source of light, extra food and so on. Part of this from the reliability of the infrastructure and part form my years before as an offshore sailor in small boats. Here in the US in suburbia many times I find the level of preparedness is 0.

I owned a gieger counter many years ago. After having given it away to friends and in light of what seems like it will be a drawn out problem with radiation emissions from Japan in wake of their tragedy, I purchased another today. Delivery is this coming Saturday. The new machine is a Johnson GSM 505DP. The machine comes both with the pancake probe and the scintillation detector.

Aside from the fact that I like neat gadgets, what prompted this was a couple of stories I read about radiation primarily in foodstuffs and in drinking water. We had our first rain here on the Gulf Coast since the disaster in Japan. I would have loved to have been able to establish a background level and compare that to results of the rain-- and water in puddles &c to see what kind of difference might have been detectable.

So where I am going with this is-- is there any type of publication or guide on the internet to teach one how to use a counter properly--i.e.detection in drinking water for example or in food. I read about wipe tests and for the most part understand that but there is a lot about the actual use of the counter that i do not know. Any help or suggestions would be appreciated.

Thanks for the many wonderful people here and for all of the knowledge about living prepared. Additionally thanks for the interest in reading my first post.

Expat42451
 

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Not sure how you meter reads but when i was on a NBC team in the army 85 or more rads was bad news and life expecantancy greatly reduced. My self consuming anything that has been contaminated is not a good idea, hunger pains will go away but burning the lining of you stomach out is a painful way to go.
 

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I've used Geiger Counters professionally since 1967...

That Johnson with the pancake probe is excellent for the detection of minute amounts of radiation, very good at detecting contamination. Good for examining food and water for radioactive particles. For a great amount of gamma such as post nuclear detonation fallout, it would just peg off-scale and be of no use for that. It would be better to get an ionization chamber instrument such as a CDV-715 or equal. OR get a few CD dosimeters and a charger.

Radioactive Iodine (I-131) is a gas that saturates the air along with oxygen and carbon dioxide, and can saturate water and be taken up into plants that way. That is why it is almost impossible to filter out. Even gas masks may not do the job. If enough is in the air, governments usually distribute Potassium Iodate pills for people to take in order to overload the thyroid gland so it won't take up I-131.

As for goodoleboy's observations, here is a more detailed chart:
1 Sievert = 100 rads / rem



This takes a minute to load:

 

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Discussion Starter · #4 ·
Goodoleboy8205 and BasecampUSA Many thanks for the information and kind reply to my post. The meter is supposed to be here tomorrow. We have rain forecast for tomorrow night and Tuesday so its going to be interesting to see what levels will be like before, during and after the rain. I would assume that places where water collects--puddles, concentrated runoff areas like downspouts from a roof, &c would show more concentrations than say an open field. I also would assume that these same areas might show an elevated level of contamination for a while even after the water dries up, provided the particulate isnt so fine that it gets evaporated out with the water. If anyone is interested I will post what I find after the counter has arrived and both before and after the rain. I am assuming that rain concentrates the count.

Regards
Expat42451
 

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Discussion Starter · #5 ·
Received the counter. Looks completely new. Last calibration as of 2009. Managed to get it ahead of the rain. Using the scintillation detector, sitting on the front porch background was between 250 and 300 CPM this afternoon. Took the counter around to where water comes off the roof and the count went up to 470 CPM. Dry ground. Since I have no baseline I do not know whether this is an unusually high count.............

Interestingly in prowling around the house using both the scintillation tube and the pancake I came across a really hot source.... I have an old WW2 flying boat compass painted with what I am going to guess is radium. Glows in the dark. So would I if I toted it around for any length of time. Definitely not something one would want to sleep with.....

expat
 

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Wow, that is pretty high for a normal background right now, even with the events in Japan. Was it on the lowest scale? In Maine I'm averaging 35-50 cpm with the three Geiger counters I have.

Moss traps fallout, so any mossy area (gutters etc.) that a lot of water runs over will show high cpm's... I was in northern Sweden right after the Chernobyl meltdown in 1986 and the reindeer who ate the moss (thier primary diet) were pretty sick.

I trap rain / snow water in a wide bowl and filter it through a coffee filter, then I take a reading of the filter with my probe's "Beta window" open.

Yeah, the radium dials on older military clocks and compasses will really make a geiger counter buzz. I have an old Wesclock radium dial face that I use for a test source... knocks the needle right over on the lowest scale !

Received the counter. Looks completely new. Last calibration as of 2009. Managed to get it ahead of the rain. Using the scintillation detector, sitting on the front porch background was between 250 and 300 CPM this afternoon. Took the counter around to where water comes off the roof and the count went up to 470 CPM. Dry ground. Since I have no baseline I do not know whether this is an unusually high count.............

Interestingly in prowling around the house using both the scintillation tube and the pancake I came across a really hot source.... I have an old WW2 flying boat compass painted with what I am going to guess is radium. Glows in the dark. So would I if I toted it around for any length of time. Definitely not something one would want to sleep with.....

expat
 

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Discussion Starter · #7 ·
Yep I agree it is pretty high. I dont know what kind of difference it would make-- but the scintillation probe on this meter is pretty large, probably 6" long and 1 1/2" dia. Its the GLE 1 probe that the meter came with........sitting here at the computer I am reading between 300 and 350 CPM. Now---- if I switch to the pancake probe its radically different with the meter set to peak hold, running around 90 CPM. So interesting question-- the pancake probe(HP265) will read alpha, beta and gamma while the scintillation probe (GLE1)will only read beta and gamma.....it would seem like, since the GLE1 is larger than the pancake, that the GLE 1 would "capture" if one will, more gamma particles. The way that this meter is set up, with dual probes, the GLE 1 is hooked to probe #2 and according to the instructions is only set up to read CPM and not dose. One would think that dose probably could be figured out if one made the assumption that one was reading gamma and used the gamma efficiency figure for the probe and did the math......the pancake probe, the HP265 is hooked to probe 1 position and is calibrated to do CPM, to Integrate the total number of counts over a given time period (or accumulative dose in mR as does a dosimeter) and with a peak hold figure as well to indicate either peak dose or peak CPM during the measuring period. So either actual calibrated dose is apparently figured from the pancake (in mR/Hr) or CPM...and from the probe 2, only CPM. What I do not understand is why the 2 probes are so different in what they read as far as CPM other than either miscalibration or the fact that probe 2 is so much larger physically. Since I have been typing this the CPM has gone up to around 120 and is holding there. Now if I switch to measure (probe 1, the pancake) and switch the meter reading to dose rather than CPM and let the meter sit and count for a few minutes (dose being the mR/Hr scale) I read around .008mR/Hr. The meter is autoscale with the multiplier being x1, x10,x100 and x1000. The dial reads from 0 to .2 mR/Hr and from 0 to 500 CPM. The thing to do would be to set on INtegrate (the dosimeter) and let it sit for say 10 minutes and the dose multiply times 6 to get the total number of mR accumulated in an hour. BAsically the instructions say that in Integrate, what is read is the total accumulated dose received in whatever time the meter is operated in the Integrate mode os dosimeter eh? I am going to post this and let the meter run in integrate and try to post the results back in a bit.......I have no idea what difference it might make but we are right in the middle of severe thunderstorms in the area...wonder if that would make any difference in my background counts?? :)
expat
 

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The scintillator is very sensitive... was the instrument calibrated with it or with the pancake probe back in 2009?

To use the scintillator for probing Sr-90, I-131 or Ce-137 in foodstuffs, you would have to shield it with lead bricks or similar, and pass the sample right under the window. Wish I was in your neighborhood, I could show you. If it is a used probe, it may have picked up a bit of low-level contamination in a lab or something to throw it off.

If the pancake probe is peaking at 90, that could be a normal spike with all the I-131 floating around right now from Japan. Nothing to be concerned about. It will skip around 50 to 150 for a while till they get a handle on things over there at Fukushima. A person in the US would get more radiation equivalent right now from eating a banana or breathing second hand cigarette smoke.
 

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Discussion Starter · #9 ·
Calibrated with both the scintillator (on input B) and the pancake. The electronics is dual channel with the ability to calibrate both--- but in reading the service manual, one can only calibrate the "b" channel--the scintillator-- in CPM. The "A" channel with the pancake can do either CPM or actual dose. In the manual, there were cautions against possible probe contamination so I decontaminated the scintillator case, then dis assembled the probe and used lots of paper towels and windex on everything and reassembled. There may have been a little contamination on the scintillator probe because I would use the pancake on it and could tell a slight difference in readings. I no longer can detect this after cleaning but I am still varying between 300 and 400 CPM on the scintillator. One wonders if during a heavy rainstorm that background does not go up because of the possibility of super light particles being precipitated out of the stratosphere and troposphere down ot the surface level--or at the very least all the stuff that might have been up in the jet stream. Lots of the cells moving through here are mesocyclonic with tops up to between 50 and 60,000Ft...and with the convection engine that a storm like that is, one might be getting a lot of particle precipitation to the surface in water........any thoughts on that??

Thanks very much for the suggestion on lead bricks.... I need to learn to do that with foodstuffs....which brings to mind that if the probe is clean and one could find a pile of lead bricks and stick it in a tunnel, then the CPM count should go way down. If we ever get behind the dry line on these storms I am going out and try to measure water puddles with the scintillator. Which brings anouter question to mind-- you are in a pretty high latitude, where the magnetic flux lines are more concentrated closer to the surface. Have you ever checked background differences during high sunspot activity i.e. aurora? Looks like the background counts might jump during sunspots due to distortion and excitation of the magnetosphere......

expat
 

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Discussion Starter · #10 ·
Interesting. Same place I went this afternoon --the downspout--470 CPM-- is now between 650 and 700 CPM using the scintillator. This just after the rain with everything wet.

I do think I am going to call Johnson tomorrow and talk with them about the difference between the scintillator and the pancake. I suspect either a fault or an error in calibration.

expat
 

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Discussion Starter · #12 ·
Tuesday morning and just got off the telephone with Johnson. A very nice tech guy confirmed that the scintillator probe does give readings disparately higher than the pancake due to the sensitivity difference. While we were on the telephone we compared background counts--in Lewisburg WV he had around 600 CPM on a scintillator probe on the same model I have-- which made me feel not at all bad having 350-400 here. He said between 500 and 600 CPM is normal for there with a scintillator. Interesting.

I also think it worth consideration for anybody buying a survey meter, that the people at Johnson do not mind spending time on the telephone answering questions about their equipment, particularly with someone as rank a neophyte as am I. This company has much to recommend it, most particularly the "Old American" attitude of courtesy and interest in a customer who didnt even buy the equipment directly from them-- a page in human relations straight from my grandfathers' days and certainly different from a call center in the Orient!!

expat
 

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This afternoon compared to yesterday afternoon counts are down to around 250 background. The hot spot I mentioned earlier---downspout runoff is actually cooler--down to a little over 400 CPM. So enough rain cleaned out the air column, and what I measured on the ground might have been accumulate particulate from a dry spell that was run off into either the ground (absorbed) or the storm drain system.

Basecamp I am going to try your technique of gathering water, filtering it and measuring the residue. Along these lines, the University of Southern California, Berkely 's Physics department has set up their own air monitoring system in the wake of the Japanese tragedy. They use a Rigid shop vac running 24 hours a day with a HEPA filter. Every 24 hours or so they change the filter and take the old into a lab where they have a big detector that the filter fits snugly around. From there they are able to do the lab work to determine what particles exist where. This is also apparently similar to the way that the EPA monitoring system works. If anyone has looked at the site, for the individual reporting stations, EPA reports not only particle energy but also CFM of air through the unit.

An interesting and potentially useful site is here

Weather Online - current weather and forecasts worldwide

Upper right hand corner is the modeling for cloud spread from Fukashima. On the model page the runs are broken down into Iodine 131, Xenon 133 and Cesium 137. Also note the pushbuttons for Japan, Northern Hemisphere and USA. Brings to mind other questions. If one does the model runs of the 3 substances, the Xeon 133 is the most widespread with Iodine second and Cesium third. Given the molecular weights here, these are apparently daughter substances produced by whats going on at Fukashima. Xeon is a gas. Can concentrations of Xeon for example be detected by a counter of some type or does one have to use spectrography....maybe another way to ask this might be does the Xeon daughter give of alpha, beta or gamma particles that would be detectable? Ditto Iodine--I just measured a bottle of Betadyne (Iodine solution ) and it makes no difference in background count. Cesium of course is different but I gather it is a "heavier" particle witness the smaller dissipation on the model run, with Iodine second and Xeon (would the daughter particle here be gas form? ) the widest......

Which brings something else to mind. In our preparedness communities, one would need someone who would have 1) the equipment to determine direct community health questions from an incident like this ; 2) the knowledge to be able to make such calls and equally as important 3) an understudy who was equally as capable in case something happened to the "department head" if one will. Just like for exampple, an amateur radio operator, the commo guy would need at least one secondary as backup. A science officer or "Spock" if one will. Maybe not Vulcan though--unless she is pretty. Nevermind :)

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Basecamp? maybe you can help me........I have about twenty docimeters, the ones that looks like a fountain pen, and four chargers........my problem is that I am unable to zero none of the docimeters.......new batteries in the chargers, thanks.
 

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Basecamp? maybe you can help me........I have about twenty docimeters, the ones that looks like a fountain pen, and four chargers........my problem is that I am unable to zero none of the docimeters.......new batteries in the chargers, thanks.
By charger(s), I assume you have 2 ?

If BOTH your chargers don't work, borrow a third one and try it. Go to your local FEMA office and ask them to try to zero 1 or 2 dosimeters to see if your chargers might be out of whack.

Make sure you understand the "zeroing" technique... it is tricky, push ALL the way down on the dosimeter while looking through it and turning the knob till you see the "marker" move back and forth, then set it at "0". Pushing it down just enough to see the light come on is not enough presuure.

After a few days or weeks it will tend to drift up scale, that is normal. There will not be enough radiation to drive them up scale unless there is a bona-fide radiation emergency, so there is no way to test them short of sending them in for calibration, see the KI4U website, they have licensed calibration services. Other than that, if you know someone that x-rays industrial welds, you could ask them to place one or two near the aperture of the "gun" next time they take a set of x-rays. Depending on where the zeroed dosimeter is placed, you would see a considerable jump on the scale. I don't think that medical professionals will want to mess with testing dosimeters with thier x-ray equipment, you could ask.

I always wondered what the TSA would do if I insisted on wearing a dosimeter through thier new body scanner. (It would have to be a low millirem dosimeter, but repeated scans would certainly accumulate and drive up the scale). A class-action suit may require them to provide you with a cumulative report if you are a frequent flyer, but I doubt if the TSA would want to comply and possibly be sued if you came down with cancer or luekemia sometime in the future.

- BC... (who doesn't fly anymore because of all the TSA
 
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