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mathesonre
USA
4 Posts |
 Posted - 06/27/2023 : 14:01:11
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Max CPM 32400, at first we thought it was Crickets, radiation
For a couple days we heard what we thought were Crickets in our basement? And then one morning I was sitting by my GMC 500 Plus radiation meter, heard the cricket sound and also saw MAX CPM 32400. My GMC Radiation Guide's largest CPM category is "> 3000", and says "Extremely high, Evacuate immediately, report to government". I had my GMC for several years, but don't think I ever heard the alarm before, the "crickets" I thought we were hearing in our basement, over several days, was the excess radiation alarm going off.
250 feet from my location in the basement, pipeline weld testing was being done. The pipeline was uphill from us, but if direct radiation was being counted by the GMC it would have had to travel through 200 feet of earth and our basement wall. I'm guessing now that they had a gamma ray source for the test and when they pointed it in the direction of our home, the gamma rays interacted with nitrogen and oxygen in the air to produce muons which the GMC counted. I don't think Gamma Rays can travel that far through the earth.
I ran across the street with my two counters and asked them to stop! They had a Geiger counter with them, but there was no way they were getting indications like I was in my basement. The next day they mentioned adding a collimator to their process, and I never saw CPMs like that again. I expressed my concern about what they were doing, and at one point walked up to their truck where the radiation was three times background.
Over the next two days the GMC was definitely showing increases in background of 3 to 4 times, easily exceeding the default GMC alarm threshold. Most locations they were testing, a direct line to my basement would be entirely underground and 800 ft. away!I talked to the pipeline company supervisor showing him the MAX CPM 32400, and his response was, he had never had a problem of this kind for over ten years. So I think the collimator drastically increased safety.
BUT from the GMC data, I believe I have calculated that we potentially received a total dose, of some sort of radiation, at maybe as high as 32400 CPM for half an hour's time total, before we detected this and talked to them.. That's half a year's background.radiation in a half hour's time. The thing I'm still concerned about was what was the energy level of the radiation. It must have traveled through the atmosphere, the roof, attic, and first floor of our house to reach the basement, thus the muon guess???
I frequently, continuously record the GMC data, but I hadn't been when all this occurred. I believe my other very old counter was saturating, while the GMC has the high level tube. And I still wonder about the pipeline testers counter, whether it was saturating?
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Bob Matheson |
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| Reply #1
EmfDev
2150 Posts |
Posted - 06/27/2023 : 16:24:17
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| Hi Mathesonre, the first thing we need to consider is if this reading is real radiation reading and not just noise. Have you confirmed this happening at the same time with two geiger counters? That means the reading increased at the same time? Also is the truck radiation repeatable? if you go back will it still give off 3-4x the background radiation? |
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mathesonre
USA
4 Posts |
Posted - 06/28/2023 : 03:14:22
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Thanks EmfDev
Yes I do have two meters from different manufacturers and both tracked each other during the events I witnessed. Both are battery powered.
When I was sitting by the GMC and it went wild with counts, I took both my meters and charged across the street to the source of the testing. They were using a radioactive source to test the pipe welds. During my charge to the site both meters were indicating high levels of radiation. The truck the testers were using was probably 200 feet from the test site, and yes even near the truck there was a 3 times indication in background radiation by both meters.
For various reasons I have not investigated this for several months since it occurred.
I live in a very rural area so I do trust the readings I was seeing. I'm pretty sure they were using a gamma source, but can't fathom gamma traveling through 200 or more feet of earth, thus the thought about muons being generated by the gamma rays hitting atoms in the atmosphere. |
Bob Matheson |
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| Reply #3
EmfDev
2150 Posts |
Posted - 06/28/2023 : 10:38:30
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| If both meters detected the same level at that time, then that means that event is true. We dont really know what happened there but maybe it was the collimator plus strong gamma. |
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| Reply #4
mathesonre
USA
4 Posts |
Posted - 06/29/2023 : 05:10:26
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The thing that really confuses me; can gamma travel 200 feet through the earth and a concrete wall to reach my meters? I have to think the gamma source they were likely using had very high energy and was somehow interacting with the atmosphere, producing some secondary radiation. I was seeing background readings increase even when they were testing 800 feet away and the gamma would have had to travel through 800 feet of earth to reach my meters in the basement. I did talk to two different staff members at the time and they had no explanation, other than wow your meters must be really sensitive. I don't know if they realize, if the radiation levels are too high the tubes in their meter may saturate and produce an incorrect low reading. That's why some of the GMC meters, like the GMC500 plus, have low and high level tubes.
Again thanks for the help! |
Bob Matheson |
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| Reply #5
mathesonre
USA
4 Posts |
Posted - 07/07/2023 : 08:58:16
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I believe I understand, now, how we were showered with 32,400 gamma rays per minute in our house. The weld inspection process certainly, at least, sends out a cone of gamma rays which could not have possibly directly reached my counters. But I've learned that all a gamma ray has to do is ricochet off an electron anywhere in the atmosphere. This is the process that protects us from gamma rays from outer-space. So a gamma ray, or two or three (thousands), would shoot over our house, hit an electron, ricochet toward my meter (or me), and boom, a count. When the weld test crew added the collimator to their source, they significantly narrowed this cone of gamma from say 180 degrees, to 20 or 30. Why they weren't using a collimator in the first place? They were setting their meter right on top of the pipe which may have shielded it. I truly wonder what their radiation badge results were?
Thanks again for the help! |
Bob Matheson |
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Max CPM 32400, at first we thought it was Crickets
