Re: Beta measurements at Nuclear Power Plants

[Keith Welch <welch@CEBAF.GOV>]

At 09:27 AM 6/13/96 -0500, you wrote:

>     Questions:
>     
>     Is the (OW-CW)*CF method used when documenting the results of smears 
>     measured with an ion chamber or is just the (OW-CW) value reported.
>     
>     What CF is used for determining Beta Skin Dose Rate and what 
>     conversion factor is used to convert ion chamber contamination 
>     readings in mR/hr to dpm.  
>     
>     How are your CFs determined (i.e. what mix, nuclides, sources 
>     geometry,etc.)
>     
>     Thank you in advance for your response:
>     
It's been a while, but when I worked at Nuc plant, we settled on 5 (I think)
for a beta dose CF as a "standard" based on some tests that were done at our
cal facility (John Lobdell, are you out there??)  Most CFs are determined
using a U-slab (I guess because they are abundant and approximate fission
product betas) but we found that the CF was somewhat different when using
the actual nuclides of interest.

If I remember correctly, smears that were measured on ion chambers were
documented in terms of "mR smearable" units rather than attempting to
quantify dpm.  This may not be the same now.  I'm sure we did some
comparisons to determine dpm from a smear of a given open window exposure
rate, but I don't know any numbers.  Might be worth trying at your site if
you've got some hot smears.  You can probably count them in a gas flow prop.
counter with some correction possibly for high counts and
backscatter.(You'll probably contaminate the detector, but it's ok just this
once!! )

Sorry I can't be more quantitative.

Keith Welch
Thomas Jefferson National Accelerator Facility
Newport News VA
welch@cebaf.gov