Final Technical Report on Radioxenon Event Analysis

Abstract

This document was printed on recycled paper. Executive SummaryAutomated radionuclide samplers to monitor for nuclear explosions are being installed as part of the International Monitoring System. Data from these systems is being generated and tools to analyze large data sets and complex operational parameters are required. In addition, the processes to efficiently screen and categorize the samples need to be developed. This Advance Spectral Analysis for Radioxenon (ASAR) project supported the U.S. National Data Center (NDC) radionuclide sample collection objectives by researching and developing algorithms and analysis approaches and building analysis tools that can be used with the NDC database. These tools were designed initiated on the previous Data Center project, and extended and upgraded during the ASAR project. These tools provide an independent calculation approach and can be used to provide confidence in the data and activity concentrations provide by the International Data Center (IDC).In addition to the main review toolset, the ASAR project supported the enhancement of the calibration tool, which allows semi-automated calculation of the calibration data collected from beta-gamma systems. And the ASAR project supported the development of a stand-alone analysis tool, using a different analysis approach using standard spectra fitting. This was developed in conjunction with the University of Texas, with the support of Dr. Biegalski during his sabbatical at PNNL. This tool is useful for low activity concentration samples and can provide increased accuracy in the calculated values.With the increased capability in analyzing the data files and providing high-confidence values, the ASAR project focused on exploring the approaches to effectively screen and categorize samples. There are many samples collected every day, with many activity concentrations below the minimal detectable concentration. However, there are also detections every day which need to be reviewed and resolved. Almost all of these are from emissions from nuclear power plant reactors or medical isotope production facilities, but they require careful inspection and review; making this process as efficient as possible was a main focus of the ASAR project. This is an active research area and no simple approach is satisfactory. Although the systems measure four radioxenon isotopes which can provide much more information when combined in ratios that when analyzed individually, they are not always detected above the minimal detectable concentration (MDC) of the collection and measurement system. Even in cases where several or all isotopes are detected, the radioxenon data can't discriminate nuclear explosions from medical isotope production or reactor start-up in all scenarios. In these cases, additional information is required to support resolution of radioxenon detections, such as seismic detection or other information. The radioxenon data can be screened to narrow down the number of detections that require further analysis and combined with other...

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