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*

We 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. 

Recent 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 conditions.

*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.