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iceman22
Bulgaria
12 Posts |
 Posted - 05/29/2014 : 01:00:42
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Still waiting for my new 300E to turn up was doing a little light reading, hahah. Anyway, just asking does this machine display uSv/h E.G 0.01uSv/h or 5 uSv/h or even 100uSv/h or do we have to do some maths and convert ourselves ?
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| Reply #1
Alchemy2
Canada
89 Posts |
Posted - 05/29/2014 : 12:00:45
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| The unit displays the readings in CPM and uSv/h as well as mR/h. Also, in text mode the total counts during the measurement cycle is also displayed. Approx 200CPM~1uSv/h FYI. |
The more I learn, the more I realize I do not know! |
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| Reply #2
iceman22
Bulgaria
12 Posts |
Posted - 05/29/2014 : 21:33:04
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quote:
Originally posted by Alchemy2
The unit displays the readings in CPM and uSv/h as well as mR/h. Also, in text mode the total counts during the measurement cycle is also displayed. Approx 200CPM~1uSv/h FYI.
great, sounds like they are good little machines! I was reading and watching some stuff about fukushima. They were getting readings on their little portable machines, of upto 112uSv/h but they were dressed up for it. They were saying anything near 80 to 100uSv/h is time back away quick, and you don't want to be too long in a place which has readings of 15 to 20 uSv/h unless your dressed for it. WOW! what a mess that place is, and it's getting worse, with number 5 going west too.  |
Edited by - iceman22 on 05/29/2014 21:34:02 |
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| Reply #3
Alchemy2
Canada
89 Posts |
Posted - 05/30/2014 : 06:55:34
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Yikes! too Hot for me... lol
Yes, mine seems to be working well. As I said, both my GMC-320+ and my JB-4020 dosimeter read very close, both have the 4011 tubes in them. My 4020 on 1.0s integration is VERY sensitive and responds slightly faster to changes in levels than the GMC-320+. When I set the JB unit to 30s integration time-average mode, which is its power-up default setting, it reads average levels within +/-0.02uSv/h or less. The JB-4020 was less $$$ than the GMC-320+, but it does not read CPM, only uSv/h and total accumulated dosage (resettable) in uSv. The JB unit apparently is calibrated to a Cs-137 test source before shipping. No clicks or indications other than exceeding alarm levels (visual and vibration can be set on it).
Backgrounds here rarely exceed 0.12uSv/h (0.012mR/h), only an odd cosmic ray event might spike it up towards 0.15-0.18uSv/h on occasion. Pretty happy that low BG levels are here. My GMC reads usually a BG ~15-20CPM on average - that's about one event every 3-4s.
I plan to use my GMC-320+ for evaluating background 222Rn levels in my basement. I have almost all the stuff needed now (charcoal, 4.1" dia. x 1.2" deep circular tins, mesh, just awaiting silica, and need to make a barrier for diffusion). I did a lot of research and have a good way of using our units to do a 3d test, with a 3h lag time before counting (to allow for secular equilibrium between daughters of adsorbed Rn).
Given what I am seeing in my BG basement levels, I doubt if I have barely any Rn gas present, but it'll be a good experiment for little $$$.
Darren
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The more I learn, the more I realize I do not know! |
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| Reply #4
Alchemy2
Canada
89 Posts |
Posted - 05/30/2014 : 07:15:15
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Iceman,
one thing to be aware of is that Fukushima levels are lower now than when they initially had releases. Plumes diffuse in ocean water very quickly. I would not want to eat anything within a 400km radius of that site to be sure, but I think that the media sometimes over plays the affects of this incident. It has created a LOT of anti-nuclear hype over the past year or so.
Once the containment is achieved, NORM levels won't be affected by much at all. It'll probably take 10 years for that to happen.
I have a M.Sc. in physical chemistry, and have taken a couple of radio chemical courses during my Ph. D, so having that under my belt (though a bit rusty after 25 years, but got back up to speed fast! lol) helps put these things into perspective.
FYI, that secular equilibrium I mentioned is a condition when in a sealed environment, a parent nuclide like 222Radon (222Rn) has the same radioactivity as its daughter products in its decay chain. This only occurs when the daughter nuclides decay significantly faster than the parent, and is around 5-10 half life duration for the next daughter in the series.
For example, let's say element A decays to B and C. A decays at a half life of 4 days, but B->C at a rate of 8h. It should take between 40-80h in a sealed container to have all the activities reach close to 99% of equilibrium, so that activity of A, B, C are the same.
In a plume or release situation, obviously this cannot happen, as the products are dispersed and diffuse into the environment unequally.
I saw some data for Winnipeg here showing a Cs-137 spike late summer 2013. Not sure what caused that, since it was not seen everywhere, but perhaps a release event occurred. Looking into that. The levels were still very low, and I wish I had my unit back then to see if it would have recorded that. (most like need a rain event to read those levels where the Cs-137 is absorbed into the water during rain. Not sure.
Have a great day!
Darren |
The more I learn, the more I realize I do not know! |
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| Reply #5
iceman22
Bulgaria
12 Posts |
Posted - 06/05/2014 : 22:45:19
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quote:
Originally posted by Alchemy2
The unit displays the readings in CPM and uSv/h as well as mR/h. Also, in text mode the total counts during the measurement cycle is also displayed. Approx 200CPM~1uSv/h FYI.
Hi just had it through, nice little machine! BUT, it seems first off it is counting background in home of around 14 to 22CPM which I think, is so bad. The thing is 14 to 22 CPM how do I switch to get mR/h as I only seem to be able to switch to a graph or number count CPM, and then as you say there is the uSv/h how do we switch to get that ? Please.. |
Edited by - iceman22 on 06/06/2014 00:42:23 |
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| Reply #6
Alchemy2
Canada
89 Posts |
Posted - 06/07/2014 : 08:08:12
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Iceman,
Okay. First off - remember that a count of 14-20 CPM is pretty good and rather normal. We are bombarded by cosmic rays too, which hit us every day. Some will hit the atmosphere and cause some upper air reactions (like forming 14C, 18O and 3H (tritium)) and others will pass right through the atmosphere and hit us, or pass through us. These are high energy gamma rays but some of their energies will register on the unit too. We also have what is known as NORM - naturally occurring radioactive materials - like 40K which is potassium 40, a gamma emitter in very low abundance present is many foods, like bananas, spinach, broccoli, etc.
Carbon 14 (14C is also created by cosmic rays) occurs in small amounts too.
Uranium and daughter products are known to be present is trace amounts all over the earth, and on occasion will decay and a gamma ray from one of the daughter decay products will ping the unit too. Totally normal. We actually have radioactivity form natural sources all about us. Only when levels get much larger, like from fallout, etc., should we be concerned. Nice thing with your 300 unit is that it will detect this if present.
Okay - changing scales: in the large font mode, you can change to mR/h by pushing the up arrow key until selected. You can get cpm, uS/h, and mR/h showing depending upon the selection.
I get around 20CPM here on average in Winnipeg. that is a pretty low background. On occasion, like right after a rain storm, I can get a bit higher, maybe 30cpm.
Hope that this helps!
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The more I learn, the more I realize I do not know! |
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| Reply #7
iceman22
Bulgaria
12 Posts |
Posted - 06/08/2014 : 03:58:10
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Thanks for the help again, yep your right, but found out by playing around with it, I am more of a hands on type, and watch and see where it leads to! hahha. its when I get lost, I turn to the books, not always the best thing to do, but most of the time it works out... |
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uSv/h
