A novel method for estimation of CAM filter head collection efficiency

Air sampling in a nuclear industry plays a major role in determining the effectiveness of confinement, assessing the workplace air activity levels, determining the posting requirements and to warn of significantly elevated level of airborne radioactivity. Continuous Air Monitor (CAM) is located at pre-designated locations with anticipated higher air activity potential, for early detection enabling prompt warning to the workers. The performance of CAM is highly dependent upon two factors namely particulate collection efficiency and detector efficiency. Detector efficiency is easy to determine using standard sources either insitu or externally while collection efficiency solely depends upon the design and operation of the filter head of the CAM unit. Smoke test is regarded as an easy qualitative way to determine the collection efficiency by visual examination. This paper utilizes the optical density measurement of the filter papers subjected to smoke test and presents a method to quantify the particle collection efficiency in terms of relative optical density. The technique was validated by DOP testing at the HEPA filter testing facility and the value matched within ±2%. (author)