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Author Topic: Personal Radiation Dose Equivalent Rate Measurement  (Read 7141 times)

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Offline kestrel452

Looking for some advice from the brilliant minds of NukeWorker  :)

What relatively affordable instruments (~$600 and under) would you recommend for reading radiation levels in an exposure unit accurately? I've taken a look at a few different units: Ludlum Model 25, GammaRAE II R, and Mirion DMC 3000.

Ion chamber instruments, like the Ludlum 9, seem to limit themselves in detection range. They top out at 50R/hr, and have an energy response accuracy of 20% which isn't anything stellar compared to the accuracy of most of these personal dosimeters.

The GammaRAE II R has an energy response accuracy of 20%, and only detects gamma. RAE Systems makes no mention of x-ray, beta, or neutron detection. While I probably wouldn't ever need neutron detection, no dose equivalent measurement of x-rays or beta seems like a let down.
http://www.raesystems.com/products/gammarae-ii-r

Mirion Technologies claims the DMC 3000 is typically accurate to within 10% of the true value for gamma and x-rays from 60keV to 3MeV. It also has an attachable beta module to allow (what I assume to be) the DER of beta radiation to be included in the DMC 3000's total reading. I'm unsure exactly how the beta module works, this is merely a presumption. The energy response is the best I've seen on paper, +/-10% from 16keV to 7MeV for both x-ray and gamma.
https://www.mirion.com/products/dmc-3000-electronic-radiation-dosimeter/

The Ludlum Model 25 is unlike the other two, in that it uses an energy compensated GM tube in lieu of a photoelectric PIN diode. As I understand it, photoelectric "PIN" diodes are the solid state equivalent of ion chambers. It's energy response accuracy is a respectable +/-15% from 60keV to 3MeV. It has a huge detection range of 0.02 mR/hr to 999 R/hr What's confusing is they list both a "beta response" and "neutron response" in its specs. I'm not sure if this means it measures beta and neutron radiation in an accurate dose equivalent rate, or what. A caveat Ludlum puts on the Model 25 is that it "might not be suitable" for measuring background radiation. Seems like a strange shortcoming, how much of a deal break would it be?
http://www.ludlums.com/component/virtuemart/personal-radiation-monitor-9-detail?activetab=specifications


Any help trying to understand all this is appreciated. I have no idea what to determine is "best" given the data.

Offline Rennhack

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #1 on: Aug 29, 2015, 05:06 »
What is the intended use?

Offline SloGlo

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Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #2 on: Aug 29, 2015, 05:42 »
"
Any help trying to understand all this is appreciated. I have no idea what to determine is "best" given the data.
"

best wood bee determined by application, as mike as asking.
 

 
 
 
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Offline kestrel452

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #3 on: Aug 29, 2015, 05:56 »
What is the intended use?

Sorry, that should have been made clear in the OP.

It's for hobbyist and radiological emergency type use. So I guess "best" for determining the most accurate dose rate and accumulated dose for a given gamma/x-ray (and preferably including beta) radiation field. I'm not a health physicist, nuclear power plant engineer, or in nuclear medicine. I don't need anything super-specialized.

Thanks!  :)
« Last Edit: Aug 29, 2015, 06:15 by kestrel452 »

Offline roosterfitz

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #4 on: Aug 29, 2015, 05:59 »
Send me a PM and I would be glad to give you a primer on radiation detection and measurement instrument selection. pete

Offline Rennhack

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #5 on: Aug 29, 2015, 06:59 »
Sorry, that should have been made clear in the OP.

It's for hobbyist and radiological emergency type use. So I guess "best" for determining the most accurate dose rate and accumulated dose for a given gamma/x-ray (and preferably including beta) radiation field. I'm not a health physicist, nuclear power plant engineer, or in nuclear medicine. I don't need anything super-specialized.

Thanks!  :)

Then you probably don't need a meter that goes over 50R/hr, which was one of your complaints of the Ludlum 9.  You are not likely to see more then a few mR/hr.
« Last Edit: Aug 29, 2015, 07:01 by Rennhack »

Offline kestrel452

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #6 on: Aug 29, 2015, 07:16 »
Then you probably don't need a meter that goes over 50R/hr, which was one of your complaints of the Ludlum 9.  You are not likely to see more then a few mR/hr.

You are correct, though the personal-sized units have better energy response accuracy on paper anyway. They're also less expensive. The 50 R/hr limit wasn't really a deal breaking factor, just something I noticed about the traditional ion chamber detectors.

If there's something I'm missing (quite possible) about these ion chamber units, and they're more accurate/useful for whatever reason please share your input. My question was more directed towards these photoelectric diode and pocket energy compensated GM meters.
« Last Edit: Aug 29, 2015, 07:18 by kestrel452 »

Offline kestrel452

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #7 on: Aug 30, 2015, 01:12 »
Side question:

What radiation detection/measurement book would you recommend for someone who has a very basic understanding of radiation? I'd prefer one that has a relatively wide breadth of material, rather than a mile deep set of information for a few concepts. Types of radiation, why/how they emanate from atoms, types of detectors, detection methods/units, exposure limits/effects, well you get the point, etc.

I've seen Atoms, Radiation, and Radiation Protection by James E. Turner; and Radiation Detection and Measurement by Glenn F. Knoll. Not sure which one is better for a generalist/hobbyist, or if there are better more easy reading books out there.
 
Thank you!
« Last Edit: Aug 30, 2015, 01:12 by kestrel452 »

Offline HydroDave63

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #8 on: Aug 30, 2015, 03:54 »
Sorry, that should have been made clear in the OP.

It's for hobbyist and radiological emergency type use. So I guess "best" for determining the most accurate dose rate and accumulated dose for a given gamma/x-ray (and preferably including beta) radiation field. I'm not a health physicist, nuclear power plant engineer, or in nuclear medicine. I don't need anything super-specialized.

Thanks!  :)

If it doesn't require EMP hardening and just general "educated guess" measurements, pancake probe on a Ludlum Model 3 should suffice.

If you want your instrument to survive the opening bell of the Apocalypse, there is always the UDR-13.

Both of these instruments can be found on eBay. You might be able to outbid me on one, if it is your lucky day  8)

Offline SloGlo

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Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #9 on: Aug 30, 2015, 10:06 »
Side question:

What radiation detection/measurement book would you recommend for someone who has a very basic understanding of radiation?

"an introduction to radiation protection" by alan martin & samuel a. harbison, while old school and out of date on some regs is a good lay reader. 
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Offline Bonds 25

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Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #10 on: Aug 31, 2015, 01:10 »
You are correct, though the personal-sized units have better energy response accuracy on paper anyway. They're also less expensive. The 50 R/hr limit wasn't really a deal breaking factor, just something I noticed about the traditional ion chamber detectors.

If there's something I'm missing (quite possible) about these ion chamber units, and they're more accurate/useful for whatever reason please share your input. My question was more directed towards these photoelectric diode and pocket energy compensated GM meters.

An Ion Chamber is considered a true dose rate meter. So unless you are performing characteristic surveys on irradiated components underwater, 50 rem/hr will be more than enough.....you better hope.
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Offline OldHP

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Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #11 on: Aug 31, 2015, 01:50 »

It's for hobbyist and radiological emergency type use. So I guess "best" for determining the most accurate dose rate and accumulated dose for a given gamma/x-ray (and preferably including beta) radiation field. I'm not a health physicist, nuclear power plant engineer, or in nuclear medicine. I don't need anything super-specialized.  Thanks!  :) 

For hobbyist use, you'd probably be better off with a cheap micro-R IC than something that will measure above 50 R/hr or as HD said "a GM pancake", i.e. a frisker.
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Offline kestrel452

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #12 on: Aug 31, 2015, 02:56 »
Thanks guys for taking the time to reply.

I actually have a relatively new Model 3 and 44-9 probe. This only get's used for measuring count rate of ore samples and whatnot.

The reason I'm looking into ion chamber and photoelectric diode type meters is for true dose rate measurement, as Bonds25 pointed out.

I'll have to look up the micro-R, haven't seen it before. How does it compare to the Ludlum 9? What's the advantage of a true ion chamber detector over a photoelectric diode personal dosimeter like the DMC 3000? Is either better at getting a true radiation field's dose rate? I suppose that's what this thread is really coming to: pocketables vs full size ion chambers.

Offline Rennhack

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #13 on: Aug 31, 2015, 04:45 »
With an Ion Chamber, 1 in = 1 out.  With other detectors based in the '6 region curve', they are proportional, and each have their own limitations. Some respond slowly to low levels or over saturate at high levels like your GM. 

Offline SloGlo

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Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #14 on: Aug 31, 2015, 08:41 »
iffen yins want a meter fore true dose rate data, ya should calculate the calibration fees into yore pricing. without a current calibration, yew have know basis of knowledge as to watt the meter is reading, merely an approximation. small button sources can be bought four low level exposure cals. the larger a dose rate you want two measure, the larger the source will bee kneaded. at sum point, a license will be required to have the radioactive sources.

a less expensive weigh is to buy  the electronic equipment to pulse cal the meter, witch can do any range of dose of interest.

an annual fee to a certified calibration facility is most likely the most hobbyist friendly path. depending on the meter and type of procedure (source oar pulse) cost range should bee in the low hundred dollar range.
quando omni flunkus moritati

dubble eye, dubble yew, dubble aye!

dew the best ya kin, wit watt ya have, ware yinze are!

Offline GLW

Re: Personal Radiation Dose Equivalent Rate Measurement
« Reply #15 on: Aug 31, 2015, 09:11 »
iffen yins want a meter fore true dose rate data, ya should calculate the calibration fees....

eeyup,...

kinda like we were called out to the scrap yard,...

'cause they got a big gray cabinet with GE logos all over it and a tiny little tri blade inside one of the meter faces,...

a big, gray, built by GE cabinet, which had been setting out in the environment of a four season region of the US of A under all kinds of other scrap for at least a dozen years or so,...

which got turned over by some new kid at the scrap yard and there it was,..

the dreaded silver & black tri blade,...

you'd have thought that cabinet had a Jack Tatum jersey on it,...

and the scrap yard got this cool as can be "Emergency Radiation Kit", courtesy of Ludlum, Inc.,...

and who knows how many HSD grant dollars,...

but when someone at the scrap yard remembered about the fancy kit they got from the HSD guys, and then that someone opened it up, there were these tan colored boxes with switches and scales and cables and batteries in foam cutouts and no one knew what to do,...

so they called us,...

and we showed up, as good neighbors are wont to do,...

and the calibration stickers were legible, and still shiny and six + years overdue,...

way too much ado about Pm-147,...

but they did buy us lunch,....

which was nice,...

and so, with my two cents running into a dime,...

amateur radpro is just that,........................amateur,... [coffee]

been there, dun that,... the doormat to hell does not read "welcome", the doormat to hell reads "it's just business"

 


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