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Re: Lab Surveys:criteria for Contamination



>1.Do you use greater than 2X or 3X background?

We do not draw a specific line in the sand. If we find contamination
(usually by LSC) that is enough above background that we are sure it is
there, we call them and tell them what we found and where. This is done
because we may  not have found the highest spot. Researchers seem to
appreciate these calls because this helps them with experimental cross
contamination issues. I guess that the best value we can say is "sure it is
there" is about 2X bkg.

>Do you use the the NRC guidance of 200 dpm beta and 20 dpm alpha, for
>removable and 2000 dpm beta and 200 dpm alpha, for fixed contamination?
>If so, what instruments do you use to determine the dpm, and how are they
>calibrated? For example, how do require the researchers to calibrate their
>>liquid scintillation counter and/or GM counter for the different isotopes?

We work with them to get "good" results. The problem we see most often is
having the settings wide open and causing a high and erroneous background.

>Do any of you have strong arguments for or against either of the above
>methods?

No.

Paul Lavely
lavelyp@uclink4.berkeley.edu


>Ninni Jacob
>Radiation and Biological Safety Officer
>Office of Risk Management
>Brown University - Box 1914
>164 Angell Street
>Providence, RI 02912
>email: Ninni_Jacob@brown.edu



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