On-line measurement of stack gas particulate radionuclides

Stack gases from nuclear facilities can contain both natural and man-made radionuclides. Interferences from natural radon daughters limit the detection capability of common radiation measurement methods. An improved system using on-line multichannel analyzers, alpha energy spectroscopy, gamma-ray analysis, radon-compensated gross beta counting, and automated data reduction is presented. This system provides accurate determination of certain stack effluent fine particulates as air concentrations at or near the derived concentration guides alarms at preset levels. The system, the moving filter radioactive aerosol monitor (MFRAM), is an adaptation of the transuranic aerosol measurement system developed by the Lawrence Livermore National Laboratory. The MFRAM controls a high-temperature sample stream to minimize mass formations that degrades alpha spectroscopy results. It features an alpha energy analysis (AEA) algorithm for automatic internal energy calibration with resolution compensation and spectral peak extraction. The AEA program reports 239Pu, 212Bi, and 212Po as air concentrations; 212Po is used to compensate for the radon contribution to gross beta measurements. The resultant beta measurement is used to determine the long-lived radionuclide gross beta concentration