Design and operation of an automated beta-particle counting system for the measurement of 220Rn (and 222Rn) progeny

Abstract

A fully automated system of the continuous (active) type has been designed for the unattended quantification of 222Rn progeny and 220Rn progeny in calibration and test facilities, as well as working and living environments. The system uses a beta-particle detector and associated electronic circuitry, in conjunction with an in-house microprocessor-based processing interface card and a personal computer, operated by specially developed in-house software. The system represents a significant improvement over systems using alpha-particle detectors because of its enhanced flexibility of design and virtual elimination of plate-out effects in the sampling head, and of self-absorption phenomena in the sampling filter. The beta-particle system was tested and calibrated in a Radon/Thoron Test Facility (RTTF) of the walk-in type under a variety of experimental conditions. For the geometry used for this system, the Potential Alpha Energy Concentration (PAEC) in air can be calculated by the expression PAEC -264 Nbeta (cpm/microjoule*m-3), where Nbeta is the beta-particle system count rate in counts per minute (cpm).