Re[2]: Beta rule of thumb

["MIKE RUSSELL" <russelmj@songs.sce.com>]

  Keith,

  Here's my two cents.

  I've always interpreted these "Rules of Thumb" not for converting activity to
  dose rate but rather converting measurements made by friskers to measurements
  made by ion chamber survey instruments.

  This is useful in comparing contamination survey measurements made by an
  survey meter when the count rate is too high to be handled by a frisker.

  Our empirically derived conversion is 10,000 cpm on a frisker (pancake GM
  tube) equals 1 mR/hr on an RO-2 (open window).

  This value (100,000 dpm/mR/hr) is about 5 times higher than the value
  you quoted below.

  mike russell
  russelmj@songs.sce.com






Randy,

Mark is asking about a ROT, which, by nature incorportates a bunch of
assumptions, and he's also truncating the units (all good rad-techs speak a
shortened form of the incredibly cumbersome techno-jargon which abounds in
HP).  Apparently it's been too long a week - you're over-analyzing :)

Anyway....
Mark, my old rule o' thumb gives slightly different levels for the gamma.
But it's in the ballpark.  I get 2,000,000 dpm to one mrem/hr.  But what's
a million dpm among friends.  My beta dose rate conversion is a factor of
100 higher.  i.e. the same 2 million dpm gives 100 mrem/hr or conversely,
it only takes 20,000 dpm to yield 1 mrem/hr.

Anybody have numbers terribly different from this?

---------------------
>Date: Thu, 02 Oct 97 10:49:34 EST
>From: "Norman Randy" <rnorman@smtplink.microbio.com>
>Subject: Re: Rule of Thumb for BETA contamination
>
>     Something escapes me here...isn't dpm "decays PER MINUTE" and mrem a 
>     unit of dose? The dose received via exposure to a certain number of 
>     dpm (or uCi, etc.) depends (among many other things) upon the total 
>     time of exposure. The same activity can yield a very low dose or a 
>     very high dose, depending upon the amount of time one is exposed, no??
>     
>     I though this was a basic concept...am I missing something here? Are 
>     there assumptions being made that are not explicitly stated? 
>     
>     Come on now, it's already been a long week..no fair playing games with 
>     my head!
>     
>     Randy Norman
>     Safety Manger, RSO, CHO, BSO, etc.
>     MA BioServices, Inc.
>     Rockville, MD
>     rnorman@microbio.com
>
>
>______________________________ Reply Separator
_________________________________
>Subject: Rule of Thumb for BETA contamination
>Author:  radsafe@romulus.ehs.uiuc.edu at INTERNET
>Date:    10/2/97 8:46 AM
>
>
>The rule of thumb conversion for removable contamination has been 1 mrem 
>gamma = 1 million dpm
>assuming Co-60 as the major isotope does anyone have a rule of thumb for 
>1 mrem BETA ? 
>     
>I'll welcome any input 
>
Keith Welch
Thomas Jefferson National Accelerator Facility
Newport News VA
welch@cebaf.gov
Ph: (757)269-7212
FAX:(757)269-5048