[ RadSafe ] Cardiolite Fate

Hansen, Richard HansenRG at nv.doe.gov
Wed May 19 13:37:34 CDT 2010


Another thing to keep in mind is that the Ludlum Model 19 Micro R Meter is energy dependent.
The uR/h rate shown on the display will over-respond to gamma rays with energies below the 662-keV gamma rays from Cs-137 that the Model 19 is usually calibrated for.

The 140 keV gamma rays from Tc-99m will cause an over-response of over 700%, and the gamma rays of 69-167 keV from Tl-201 will cause an over-response of 600%-700%.

So your measurement of 5000 uR/h (50 uSv/h) on the Model 19 was probably was actually only an exposure rate of around 700 uR/h (7 μSv/h). 

For more info, see the chart "Energy Response for Ludlum Model 19" in the Model 19 User's Manual available on Ludlum's web site at:

Best regards,
Rick Hansen
Senior Scientist
Counter Terrorism Operations Support Program
National Security Technologies, LLC, for the U.S. Dept of Energy
P.O. Box 98521, M/S NLV128, Las Vegas, NV 89192-8521
hansenrg at nv.doe.gov


Yesterday I received both Tl-201 & Tc-99m as a intravenous cocktail during a
cardiac stress test.  The dose was 3 mCi Tl-201 and 20 mCi "Cardiolite"
Tc-99m for imaging.  By the time I got home, I was quite radioactive, with
my Ludlum Model 19 measuring 5000 uR/Hr at a distance of 4 meters.
According to the information that I received, the test amounts to a 3.45 REM
total effective dose.

Dan ii

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