Meeting new challenges in radon measurements service with solid state alpha track analysis

Full text: The national and international legislation on the control of exposures to radiation now covers exposures to the naturally occurring radioactive materials (NORM), with particular emphasis on radon in workplaces. Consequently, many more working environments have now been brought to the realm of radiation monitoring. This is mirrored by a corresponding increase in the demands for radon monitoring service. The new challenges occasioned by the increase in demands are illustrated in this paper. The paper also describes the new integrated radon measurement system at the ENEA ION-IRP radon-in-air testing laboratory, designed to meet the new challenges. In this presentation emphasis is laid only on the special features, hardware and software, of the measurement system that directly result in enhancement of the overall throughput and the quality of the radon service. In addition the use of a new technique based on a numerical filtering of the main physical parameters of the alpha track analysis used to determine the radon exposure with a CR-39 detector is presented, with particular emphasis to the quality improvements of the measurement. The readout procedure adopted by the Enea radon Service is based on track analysis by light microscopy. Since the dimensions of the tracks are significantly affected by the light intensity, the illumination of the field of view (FOV) has to be as homogeneous as possible, in order to avoid sensitivity dependence on track position in the FOV. The lighting variation could be severe, especially at the borders or when a rectangular FOV is used. The coefficient of variation of the FOV light uniformity has to be periodically checked to maintain the variation below an acceptable limit, whereas if the results exceed this value a remedial action is mandatory. The numerical correction procedure here presented results effective. (author)