What are some expert opinions and advice for buying a dosimeter?

[girts]

I've been doing some searching and price comparison yet I would love to hear some expert opinions and advice.
I am looking for a dosimeter , not necessarily the cheapest but also not a perfect lab working device. My main goal is to to learn about dosimetry and radiation and also ofcorse out of interest.
I will also at one point in the forthcoming months will go to Chernobyl, possibly also inside the plant itself.

I am currently setting my sights on the Gammascout, any thoughts about it? I see some cheaper analog ones on ebay, the ones that were produced by the CDC back in the day of the Cold war, but the drawback for me seems their size, on the plus side is probably their longevity due to their robust design and simply electronics. One could probably change some older caps inside and inspect it and it is good to go, not sure about the geiger-muller tubes inside probably they would need a change.

Also on the other hand I have seen folks upgrade their gammascout digital ones after years of service with a larger more sensitive tube etc.

So what do you think?

 

[gleem]

What is the purpose of your purchasing this instrument?

 

[girts]

Well I've always been fascinated by radioactivity (not only that but including) so now that I am doing more with it it is rather nice if you have a way to measure it.
As i said there is a plan to visit chernobyl for both exploring and learning purposes but i have been previously in another nuclear power plant and then i had to use what they gave me , having my own instrumemt especially if it is a good one would be a benefit although it is somewhat a luxury item for me at least for now because the price is rather high but i won't use it every day.The gammascout seems appealing to me from both techical cgaracteristics and also desing yet it cists about 400 usd so well what would be your advice?

 

[gleem]

Measuring and interpreting radiation instrument readings is not as straight forward as you might expect. GM counters only give accurate reading for radiation for which they are calibrated and the difference in calibration factors can vary by factors of up to 5 for different gamma ray energies. GM counters are not sensitive to neutrons. They are sensitive to Beta particles but this radiation does not contribute to whole body dose equivalent so if you have betas mixed with gamma's your whole body dose equivalent will be erroneously high.

I would think reactor operators would discourage anyone from bringing in their own dosimeter since they have no control over its calibrations and interpretation of the reading.

And to be honest I discourage the sale of such instruments to the general public. As for the Gammascout It think for general survey work I.e. measuring the exposure rate of a gamma/xray source I am not sure it is worth the money. You are probably paying for its ability to integrate the dose rate. Also Its quoted sensitivity 0.01 uSv/hr seems too high for the size of the GM tube and should be closer to 0.1 uSv/hr at best.

 

[girts]

I read your reply as a little discouraging , well with regards to radiation i would consider myself above average , well my aim is to learn and experience measuring in real time, the thing with analog dosimeters is that it is complicated if not impossible to calculate the average dose over time, i would greatly appreciate any advise

Well surely neutron detection would be done better with a scintallator but if not directly in the proximity of the fuel or reactor active components , do the average background in places like the exclusion zone consist not mostly of betas and gammas instead of neutrons?

 

[gleem]

I read your reply as a little discouraging , well with regards to radiation i would consider myself above average , well my aim is to learn and experience measuring in real time, the thing with analog dosimeters is that it is complicated if not impossible to calculate the average dose over time, i would greatly appreciate any advise

Sorry about that but as I said determining meaningful dose equivalent estimates is not straight forward. An analog instrument gives the instantaneous dose rate from which you can estimate the dose over a given time trivially. If the dose rate varies greatly or is low and the reading fluctuates significantly (< 0.5 uSv/hr) then this is a problem but below 0.5 uSv/hr is about background. $400 seems a bit expensive for what a cheaper instrument can provide. I take it this is not for any scientific study just to get an idea of radiation levels. Since your visit to Chernobyl is probably a one time event and unless you suspect another nuclear incident in which you may be involved and need a dose assessment I don't see spending that amount for the instrument. A priori there is no reason to believe that a more expensive unit will be a better choice if all you need is dose rate and integrated dose.

 

[Bigjoemonger]

Well first it should be noted if you're going to chernobyl then they will assign you proper dosimetry.

Second the gamma scout, along with other survey meters are not good for measuring accumulated total body dose. Sure it has that capability but in reality while you're walking around in a radiation field it won't be pinned to your chest. It'll be in your hand moving up and down as you wave your arms, It'll be in a backpack or your pocket. It won't give you an accurate measurement.

Handheld survey meters like the gamma scout, rds-31 or radeye b20 are good for exploring the world of radiation detection but if you're wanting to measure dose then you need an actual dosimeter. I use the dmc 3000 self-reading dosimeter at work. Something like that you can just pin to your chest and then it doesn't matter what you do with the survey meter you still get an accurate result.

 

[mfb]

You get an accurate result for your chest. If you have sources near your hand that dosimeter won’t recognize that properly, for example.

 

[Bigjoemonger]

You get an accurate result for your chest. If you have sources near your hand that dosimeter won’t recognize that properly, for example.

True but healthwise there is a difference between total body dose and dose to the extremities. They cannot simply be added together. Internal organs are more susceptible to radiation therefore they cannot handle as much dose as the hands or feet.

 

[gleem]

The TLDs that the hospital provides can't do the same an EPD can.

But the TLD's do what they are supposed to, provide a permanent record of the dose you have received over a given length of time according to regulations that are promulgated by the Federal and State governments. As a former hospital RSO, I would not be all that happy having personnel whose training in the use of the instrument is unknown running around with an instrument whose calibration was not available and whose care and use history was unknown. My advice is, do not take it to work. If you have any concerns tell your RSO.