OSIRIS—Gamma-ray spectroscopy software for on-site inspections under the Comprehensive Nuclear-Test-Ban Treaty

Abstract

We have designed and tested software for the acquisition and analysis of high-resolution gamma-ray spectra during on-site inspections under the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The On-Site Inspection RadioIsotopic Spectroscopy-OSIRIS-software filters the spectral data to display only radioisotopic information relevant to CTBT on-site inspections, e.g., 131 I. A set of over 100 fission-product spectra was employed for OSIRIS testing. These spectra were measured where possible, or generated by modeling. The test spectral compositions include non-nuclear-explosion scenarios, e.g., a severe nuclear reactor accident, and nuclear-explosion scenarios such as a vented underground nuclear test. Comparing its computer-based analyses to expert visual analyses of the test spectra, OSIRIS correctly identifies CTBT-relevant fission product isotopes at the 95% level or better.

A method for limiting data acquisition in a high-resolution gamma-ray spectrometer during On-Site Inspection activities under the Comprehensive Nuclear-Test-Ban Treaty

“…The entire code was validated against experimental measurements of fission spectra of equal sample ages [8]. Furthermore, we received 80 spectra that were generated using GEANT4 in order to demonstrate measurement restriction in references [6] and [11]. These spectra represent various sample ages starting from 2 days to 1.5 years after the event by propagating the radionuclide activities in time using the appropriate yields and decay chains.…”

“…measurement system with restrictions accomplished by software (OSIRIS) [6]. In this approach, the acquired data are completely unavailable to the user, and all analysis stages, including radionuclide identification and quantification, are automatically performed.…”

“…Measured data are not saved, but they are erased immediately after the analysis is completed. The only available information is a report specifying the presence (and activities) of OSI-relevant radionuclides [6]. Fission-product spectra were used to test the OSIRIS software.…”

On-Site Inspection RadioIsotopic Spectroscopy (Osiris) System-Integration and Field-Testing Report

“…The Osiris spectrum analysis software and the spectrum analysis test are described further in a Nuclear Instruments and Methods in Physics Research A article [17]. …”