System Tests of OSIRIS—A Spectrum-Blind Gamma-Ray Spectrometer for On-Site Inspections Under the Comprehensive Nuclear-Test-Ban Treaty
A. J. Caffrey, Ph.D.
Nuclear Nonproliferation Department
Idaho National Laboratory*
have conducted extensive system tests of the On-Site Inspection
RadioIsotopic Spectroscopy (OSIRIS) system: a spectrum-blind
instrument for the acquisition and analysis of high-resolution
gamma-ray spectra during on-site inspections under the Comprehensive
Nuclear-Test-Ban Treaty (CTBT). Unlike most other spectrometers,
the OSIRIS system does not display actual gamma-ray spectra, and its
software filter limits the display of spectral information to just
seventeen CTBT-relevant fission-product isotopes, for example, 131I.
OSIRIS system studies include an unplanned 1-meter drop test at the
former Nevada Test Site; measurements of spectrometer
energy-calibration accuracy and electronic-gain stability of the
spectrometer over the range -12 °C (10 °F) to 50 °C (122 °F); and
measurements following the decay of a calibrated uranium
fission-product source for over a year. Many of the fission-product
measurements were conducted outdoors under a broad range of ambient
*OSIRIS research and development at Idaho National
Laboratory, Lawrence Livermore National Laboratory, and Pacific
Northwest National Laboratory is supported by the Office of Nuclear
Detonation Detection, NA-222, National Nuclear Security Administration,
U.S. Department of Energy.