NUCLEONIX SYSTEMS GA720 Instruction Manual page 14

Procedure for Calibration with Source
This unit namely Gamma Area Monitor Type GA 720 has been calibrated at Radiation Standard & Calibration Lab
of Nucleonix Systems (P) Ltd., using Gamma Survey Instruments Calibrator of AEA Technology, USA. It operates
in the range of Dose rate mode (0.1 mR/hr – 100mR/hr) for Gamma Radiation.
Calibration Procedure with Gamma Source (Cs – 137 – 136.742mCi)
The instrument is calibrated with gamma instrument calibrator of Nucleonix Associates. This comprises of a 164
mCi – 137 gamma source traceable to NIST.
The monitor is pre-loaded with a lookup table for computation of dose rate. To calibrate instrument with source,
expose the detector to below dose rates and record the observed dose rates. Detector axis is to be perpendicular
to source beam. Keep the source at marked up positions for various dose rate and observe the monitor reading.
Expected
D os era te (mR/hr)
0.0 m R/hr
1.0 m R/hr
5.0 m R/hr
10.0 m R/hr
20.0 m R/hr
50.0 m R/hr
100.0 mR/hr
Very Important Note : Please note that for a required dose-rate, always choose to keep detector probe at
maximum possible distance from source with minimum no. of lead block attenuators. This is to prevent scattering
effect due to attenuator blocks at close distance (<50 cm)
Now in case a reading exceeds the tolerance of +/- 10%, of expected dose rate then adjust calibration factor or
monitor such as to make entire readings fall within +/- 10% of expected dose rate.
When the manual is dispatched to the customer, calibration factor is to be mentioned below and also saved in the
instrument program.
Over Load Test
(a) 10 Times Highest Range
(b) 50 Times Highest Range
(c) 100 Times Highest Range
Calibration Factor
Calibration Date
Calibration Due
Tested By
Date
CHAPTER - VII
CALIBRATION
:__________________
:__________________
:__________________
:
:
Observed Dos erate (mR /hr)
Passsed
Yes/No
Yes/No
Yes/No
Calibrated by :________________
Instument S.No. :________________
Approved By
Date
11
:
: