• Total rejection of gammas from outside the active detection volume 

• No lead shielding necessary 

• Signal-to-background ratio enhanced between 1 and 2 orders of magnitude (as compared to standard counting systems) 

• Easy calibration using a point source (e. g. Ge-68) 

• Large scintillation detectors are mounted outside the stack 

• Versatile Windows based software for operation and report generation

Introduction

For stack monitoring at PET-facilities, the main advantage of this coincidence technique is that outside influences due to background do not interfere with the detectors measuring the effluent within the stack.  Another advantage is that the calibration of the detector assembly is not influenced by the overall design and operation of the facility but only by the diameter of the duct and the size and spacing of the detectors.  

Varying gamma backgrounds do not influence the coincidence technique used in the low level effluent monitoring. Depending on the number and size of the detectors used, detection limits well below 1 kBq/m³ can be achieved.