Collimator Detector Effect on Design of The Radiation Portal Monitor in Gamma Radiation Detection Test According to SNI IEC 62244:2016

Abstract

BRIN’s RPM is made from NaI(Tl) Sodium Iodide crystal scintillators detectors. Due to the certification process, RPM was tested based on SNI IEC 62244:2016. This standard requires radiological tests in the form of gamma radiation detection tests by measuring radioactive statically or dynamically that are conducted by varying sources and distances. For calculating the variation of activity was using inverse-square law. This research was carried out in Serpong Nuclear Area – BRIN PUSPIPTEK. Three standards of radionuclide were used namely Am-241, Cs-137, and Co-60. In the static condition, the radionuclide source was placed in the midpoint of a distance of 2,4 m from each portal. In the dynamic condition, the source was moved through the detection area for the rate of passer-by (10 – 20 km/h). In both static and dynamic conditions, from 50 tests, a minimum of 49 alarms was triggered, the assuredness level was more than 95%. The counting results without using inverse-square law decrease with non-linear distance variations. It’s because the detector collimator opens only straight ahead causing an active area of the detector that received radiation to be smaller. The thickness of RPM’s housing frame also has a role in reducing the count value. The farther the measuring distance, the more did holder of the source blocking radiations received by the detector. This caused the different calibration factors for each counting.