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Reference, Questions and Help => Nuke Q&A => Instrument Q&A => Topic started by: rocketgirl on Jul 14, 2013, 05:24

Title: Gross alpha and beta - how low can you go?
Post by: rocketgirl on Jul 14, 2013, 05:24

I'm on a project to count gross alpha and beta in water by gas proportional counting. The boss wants us to go as low as possible but can anyone tell me how low is reasonable? We're currently looking at 1 litre samples but could go higher as we've low particulate. Can anyone help?

Title: Re: Gross alpha and beta - how low can you go?
Post by: BetaAnt on Jul 16, 2013, 01:02

It depends on what your release criteria are for your isotopes. Consult your training manual (or Basic Radiation Protection by Golnick) for MDC and MDA calculations.

Are these environmental release samples or eco-nutjob grab-a-headline study? The Univ of New Mexico wanted to build a Peace Memorial on nuclear free ground in the 1990's. The problem is there are trace amounts of nuclear fallout on every square inch of real estate. They quietly restated the siting requirements.

This is the story behind pre-atomic lead. All lead mined after July 1945 has (or may) trace amounts of radioactive fallout.

You can lower your MDA by increasing your background and sample counting times. As long as you below your release limits, don't jack up your counting times to 1000 seconds.

Normal DOE 20 DPM alpha, 200 DPM B-G.

Title: Re: Gross alpha and beta - how low can you go?
Post by: RDTroja on Jul 16, 2013, 09:00

Quote from: rocketgirl on Jul 14, 2013, 05:24

I'm on a project to count gross alpha and beta in water by gas proportional counting. The boss wants us to go as low as possible but can anyone tell me how low is reasonable? We're currently looking at 1 litre samples but could go higher as we've low particulate. Can anyone help?

The concept of 'as low as possible' shows that the boss does not know what he is talking about. There is no such thing. You can reduce background and increase count times, but there is no such thing as a perfect (i.e. 'as low as possible') counting system. That is why ALARA is not ALAP (although it started out as ALAP, it stood for As Low As Practicable which no one could pronounce or spell.)  Without an infinite count time and a true 0 background (impossible) you can't get to 0. There has to be an acceptable threshold below which nobody cares.

Title: Re: Gross alpha and beta - how low can you go?
Post by: GLW on Jul 16, 2013, 11:04

Quote from: rocketgirl on Jul 14, 2013, 05:24

I'm on a project to count gross alpha and beta in water by gas proportional counting. The boss wants us to go as low as possible but can anyone tell me how low is reasonable? We're currently looking at 1 litre samples but could go higher as we've low particulate. Can anyone help?

Yep, send me a work order and I'll come set you up,...

PM me for details,.... 8)

Title: Re: Gross alpha and beta - how low can you go?
Post by: Marlin on Jul 16, 2013, 11:10

Quote from: GLW on Jul 16, 2013, 11:04

Yep, send me a work order and I'll come set you up,...

PM me for details,.... 8)

Shameless self promotion  8)  +K

Title: Re: Gross alpha and beta - how low can you go?
Post by: rocketgirl on Jul 19, 2013, 04:39

Thanks guys, you've given me some ideas.  :)