Considerations for Data Processing by Continuous Air Monitors Based on Accumulation Sampling Techniques

Abstract

Continuous air monitors (CAMs) sample air and alarm when concentration levels of radioactivity in air exceed preset alarm levels. The air concentrations through time are calculated based on accumulation sampling techniques. Accumulation air sampling is the process in which radioactive aerosol is continually deposited onto a collection medium and a radiation detector provides continuous measurements of the radioactivity on the filter. To assess the air concentration, time intervals are established for the counting and sampling times, and the measurement of concentration represents an average over the measurement interval. There are multiple methods that can be used to determine the concentration for the most recent measurement interval, and based on the method used, each can result in significantly different values for concentrations, associated uncertainties, and response times. We evaluate and compare several methods for determining air concentrations based on accumulation counting techniques. Further, we provide a real-life example of accumulation counting and the effects of compensating for background radiation in the context of monitoring for plutonium concentrations against a fluctuating radon progeny background. Results show the importance of selecting a method that provides for a balance of response time, measurement interval, background compensation technique, and uncertainty for optimal protection of workers.