Reference, Questions and Help > Instrument Q&A
Frisking question
RDTroja:
--- Quote from: makua13 on Feb 23, 2005, 03:32 ---I been calibratin them things for years and never saw 18%, not with Tc99 anyways. Funny how numbers get larger when you get older.. ::)
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Interesting... just the other day I was thinking that some numbers get smaller as you get older...
And I never referenced Tc-99. Not sure I ever used that as a calibration source myself, but that was 100 years ago or so.
RDTroja:
--- Quote from: 870xprs on Feb 23, 2005, 07:09 ---... even though our sophisticated contamination monitors "can" see activity at much lower levels, we don't want to do that because to do so would exceed the standard set by the NRC in the generic letter. We would be shooting ourselves in the foot to look for radioactivity at levels lower than the NRC's standard. That's why we dont use a GeLi to release everything.
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I wonder what happened to that concept. If I ever get my hands on the idiot that came up with 'no detectable activity' as a limit I think I may strangle him.
And the first time someone in the position of authority recommends using a GeLi to free release something, I am coming after you, 870xprs, just for putting it in print! ;)
Shonkatoys:
The limit for Strontim is only 1000 dpm 100 cm2 where the limit for uranium is 5000 dpm 100 cm 2 therefore I would slow down even more than 1.5 inches a second to realistically check for strontium per 10cfr 835 to detect the lower limit.
For transuranics I was told you should frisk at 1 inch every 11 seconds with a 43-5 ZnS probe to meet the limits, However no one does this. Transuranics should only be surveyed with a large surface Contamination monitor if surveying buildings in my opinion. Surveying for transuranics is a joke on everysite I have been in my opinion. 20 clicks different from background give or take a few clicks in a minute. You must be crazy if you think that anyone can survey to this. Too easy to miss 500 dpm 100 cm 2.
stownsend:
There are a couple of limits for Sr90,either pure or in a mixed fission product.When you take into consideration of the energy,eff,and probe size your only looking for ~30 counts so you need to stress the turbo frisk doesn't work or as an HP help frisk them.As far as transuranics go you can't see 20 dpm/100cm2 in the field,only on lab equip.ie.tennelec or protean and frisking to the 500dpm/100cm2 total takes a trained eye .That's why we seniors make the big bucks!!!
870xprs:
--- Quote from: RDTroja on Feb 23, 2005, 09:34 ---I wonder what happened to that concept. If I ever get my hands on the idiot that came up with 'no detectable activity' as a limit I think I may strangle him.
And the first time someone in the position of authority recommends using a GeLi to free release something, I am coming after you, 870xprs, just for putting it in print! ;)
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That's ok, but I should point out that it's considered one of the rites of passage for Sr. HPs that they have to 'splain things to someone in a position of authority. That's another reason they pay us the big bucks. ;) ::)
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