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Frisking question

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coshaun:
As we all know, standard frisking rate is 1-2 inches per second. Can someone explain the necessity of slowing the scan rate to 1.5 inches if Sr90 is present? ???  Thanks for you help! 

SloGlo:
i'm at  a loss on yer question.... iffen yer acknowledged frisk rate is 1-2 inches/second, how much velocity are you losing by slowing to 1.5 inches/second?

the mostest prime rule of thumb for using a probe to measure any radiation emitting item is to not exceed 1/2 the width of the probe per second.  this'll keep ya safe whether it's a gm pancake or a half a meter gas proportional.  its the probe size to speed ratio.

Melrose:
I'm with SloGo, you haven't really slowed much.
Really don't need.  You're not going to see Sr90 anyway.  What you will see that is indicative of Sr90 is decay getting into the itrium (?)  which is about 2.2- 2.4 Kev, you'll see that across the street, through clothing, eye protection ...... yada yadayada.

Don't know if this helps you.... just insight for you

makua13:
Frisk rate based on certain isotopes and type of GM.  Lowerenergy will require slower rate in order to gaurantee that magical 95% certainty or MDA.  Maybe you want the probe closer too.?  There is always a diference between gemeric and spcific.  And by the way do youknow the efficiency of a "typical" pancake probe?  It isn't 10%, but more like 12-13%.  Then there is the thin window Alpha GM detector.  However in the end it is all not very accuate, just too many variables and too mch difference in isotopic energies.  Just do what the procedure tells you and write down the numbers "they" are looking for.

RDTroja:

--- Quote ---What you will see that is indicative of Sr90 is decay getting into the itrium (?)  which is about 2.2- 2.4 Kev, you'll see that across the street, through clothing, eye protection ...... yada yadayada.
--- End quote ---

Hi -- your friendly neighborhood proofreading PITA here...

Melrose, I think you meant MeV, not KeV. Won't see 2.2 KeV through much of anything... but 2.2 MeV will penetrate much more than you want it to. Yttrium-90 is indeed a pain to deal with. Not sure why you would need to slow down to see it. The 2.2 MeV beta may be hard to detect with a standard frisker probe designed for beta because it penetrates too well. But there are other, softer betas too. If you want some fun-with-firskers go to a plant with isotopes that decay by electron capture. They emit a soft (usually) x-ray that friskers are only 2% efficient for. Frisk a smear, its clean, put it in a SAM and it is screaming.


--- Quote ---And by the way do youknow the efficiency of a "typical" pancake probe?  It isn't 10%, but more like 12-13%.
--- End quote ---

I used to calibrate HP-210 probes on scalers and regularly get a realistic 18% efficiency. Gotta love conservative numbers and Rad-Con math. Easier to add a zero than multiply by 6 or 8.

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