Development of the Spectral Deconvolution Analysis Tool (sdat) to Improve Counting Statistics and Detection Limits for Nuclear Explosion Radionuclide Measurements

The Spectral Deconvolution Analysis Tool (SDAT) is being written to improve counting statistics and detection limits for nuclear explosion radionuclide measurements. SDAT will utilize spectral deconvolution spectroscopy techniques to analyze both β−γ coincidence spectra for radioxenon isotopes and high-resolution High Purity Germanium (HPGe) spectra that are utilized for aerosol monitoring. Spectral deconvolution spectroscopy is an analysis method that utilizes the entire signal deposited in a gamma-ray detector rather than the small portion of the signal that is present in one gamma-ray peak. Counting statistics are improved by utilizing the entire detector response and the deconvolution algorithm directly handles interferences between radionuclides. This method shows promise to improve detection limits over classical gamma-ray spectroscopy analytical techniques. The Multiple Isotope Comparison Analysis (MICA) algorithm was developed previously to demonstrate the concept for this technique for β−γ coincidence spectra utilized for radioxenon analysis. These spectra are difficult to analyze by the classical peak analysis technique due to spectral interferences among the radioxenon isotopes as well as the interferences between radon progeny and the radioxenon isotopes. The deconvolution algorithm unravels the interferences and utilizes the complete signal from each radionuclide. While the MICA algorithm has demonstrated its utility for the analysis of β−γ coincidence spectra, additional developments are necessary before this technique reaches a point where it may be applied in an operational environment. SDAT will incorporate the complete functionality of the MICA algorithm, will add in spectral weighting functions to reduce the analytical residual, and will include the ability to analyze high-resolution HPGe spectra with the deconvolution method. A significant portion of this work will involve the development of calibration methods for both radioxenon and high-resolution HPGe systems. Proper calibrations of the detection systems are especially necessary for application of the spectral deconvolution spectroscopy algorithm. The detector response from each radionuclide of interest must be individually determined. The University of Texas TRIGA reactor will be utilized to irradiate a fission product generator for production of xenon isotopes for calibration. Fission products will also be generated for calibration and testing of the SDAT algorithm for HPGe spectra. Calibrations will be conducted through experimental measurements and will also be supported through Monte Carlo N-Particle Extended (MCNPX) modeling. 770 27th Seismic Research Review: Ground-Based Nuclear Explosion Monitoring Technologies