Effluent Monitoring in Nuclear Plants Using On-Line Gamma-Ray Spectrometry

The operation of large nuclear power plants involves significant inventories of radioactive fission product isotopes. Effective monitoring of effluent streams from nuclear facilities requires the characterization of radioactivity present in operating systems to permit evaluation of potential hazards which might result from discharge of any radioactivity to the environment. The need for adequate documentation and control of effluents establishes a requirement for realtime determination of radioactivity on an isotopic basis. The purpose of this paper is to outline the application of high-resolution gamma-ray spectrometry to this problem. To meet the requirement for a practical working system it has been necessary to develop a completely automated gamma-ray spectrometer concept incorporating a remote computer operated pulse-height analyzer, calibration and data analysis techniques. An operating system will be described which utilizes a PDP-9 data system to operate a number of on-line spectrometers, providing automated data analysis and report generation. A detailed description of the techniques and hardware developed for this purpose will be presented.