Radiation Monitoring of Nuclear Power Station Stack Effluents

The key to satisfying Nuclear Regulatory Commission requirements for measuring airborne radioactivity escaping from nuclear power stations is to obtain representative samples. The impact of the problem of representative sampling was evaluated by means of a state-of-the-art survey, which is summarized in this paper. Data obtained from this study showed that there is now a pronounced trend toward the use of flow processing and sampling nozzle arrays rather than reliance upon turbulent mixing and the use of discrete sampling nozzles. An error analysis shows that the chief source of error is an inadequate number of sampling nozzles when nonuniform mixing occurs. Using the Limerick power station stack monitoring system as a model, a design description is given of an isokinetic sampling system using flow processing and sampling nozzle arrays. Potentials for improvement of this system are then discussed.