[ RadSafe ] Response of GM Meters to Higher Energy Gammas

[Leo M. Lowe]

For those familiar with survey meters, what is the relative response of 
energy-compensated GM survey meters to higher energy gamma radiation?  Such 
meters are often calibrated with Cs-137 but how do they respond to the 2.6 
Mev gamma from Tl-208 in the Th-232 decay series? This gamma contributes 
more than half of the effective dose to those exposed to natural thorium.

For example, the calibration range in the specs of the Mini-rad 1000 survey 
meters from Thermo Electron extends to 1.25 Mev.  Would such meters be able 
to properly measure the ambient dose rate due NORM materials containing 
natural thorium?  (Thermo Electron has not measured the response of these 
meters to uranium or thorium products.)

If desired, feel free to respond directly to me.
Leo M. Lowe, Ph.D., P.Phys.

SENES Consultants Limited
llowe at senes.ca
www.senes.ca
Tel: (905) 764-9380
Fax:(905) 764-9386

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