Automated QA/QC Check for Beta-Gamma Coincidence Detector

摘要

The Automated Radioxenon Sampler/Analyzer (ARSA) (Hayes 1999), built by Pacific Northwest National Laboratory (PNNL), can collect and detect several radioxenon isotopes. The ARSA is very sensitive to (133)Xe, (131m)Xe, (133m)Xe, and (135)Xe due to the compact high-efficiency beta-gamma coincidence detector it uses. As detection technology improves and more emphasis is placed on system automation, QA/QC checks become of increasing importance. By automating the QA/QC checks, the reliability of the data sets is ensured without the necessity of monitoring. Often, the automated QA/QC checks will be done on site, where radio-xenon gas is not readily available so it is important to be able to use sealed point sources as an alternative. Immediately after the initial calibration of the detector, a (137)Cs source, which has a 661.7-keV gamma-ray, is used to generate both gamma and beta spectra. The two spectra are saved to file, are called the template spectrum, and will be used as the template to perform on site QA/QC checks. The QA/QC check will automatically find the start and end points of the beta spectrum and compare them with those from the template spectrum. A similar method is used for the gamma spectrum; however, in a gamma spectrum the 661.7-keV peak can be used for the high energy end. If the points do not match, a gain and offset can be calculated to make the QA/QC spectra match the template spectra. A second and more advanced method is to take a beta-gamma coincidence spectrum for the template spectrum. A comparison of the QA/QC beta-gamma coincidence spectrum to the template spectrum will be used to determine what if any adjustments need to be made on the gain and offset. A detailed discussion of the QA/QC checks will be included in the paper.