RE: Efficiency for detection of Tc-99m

["Abelquist, Eric" <AbelquiE@orau.gov>]

John-

The detection efficiency of a GM pancake for Tc-99m is not good.  I would
estimate the pancake's efficiency to gammas to be less than 0.5% (0.005
c/dis).  One datum point that may be useful is our measured efficiency to
Mn-54, which was 0.0042 counts/disintegration.  The gamma energy of Mn-54
(835 keV) is greater than that of Tc-99m (140 keV) - so the pancake
efficiency for Tc-99m will likely be even less.  

Regards
Eric

abelquie@orau.gov

-----Original Message-----
From: Jacobus, John (OD) [mailto:JJacobus@exchange.nih.gov]
Sent: Friday, January 21, 2000 9:44 AM
To: Multiple recipients of list
Subject: Efficiency for detection of Tc-99m


Can anyone give me a reasonable detection efficiency for measuring Tc-99m
surface contamination using a GM pancake type probe?

-- John 

John Jacobus, MS
Health Physicist
National Institutes of Health
Radiation Safety Branch, Building 21
21 Wilson Drive, MSC 6780
Bethesda, MD  20892-6780
Phone: 301-496-5774      Fax: 301-496-3544
jjacobus@exchange.nih.gov (W)
jenday@ix.netcom.com (H)
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