An unsolved longstanding challenge to expand the Safeguards regime is to assay spent nuclear fuel (SNF) for its plutonium content. Regardless of the process used to assay the fissile content, there must be a gamma-ray measurement to determine the plutonium mass. Fissile material isotopic measurements in the presence of the intense gamma-ray background from (sub 137)Cs and other fission products are difficult. Plutonium-mass measurements using high-resolution passive gamma-ray spectroscopy are practically impossible due to the approximately 10(sub 7) higher activity of isotopes such as (sub 137)Cs. Assay using measurements of gamma rays with energies above 3 MeV that are emitted from the short-lived decay products of neutron irradiated SNF is more promising but still requires gamma-ray spectroscopy at rates on the order of 1 million counts per second (Mcps) or higher in the gamma-ray spectrometers due to the passive gamma ray background. PNNL has developed new digital filtering and analysis techniques to produce an ultra high-rate gammaray spectrometer that can operate at these count rates. A standard coaxial approximately 40% efficient high-purity germanium (HPGe) crystal has made passive gamma-ray measurements of SNF at a throughput of about 400 kcps at an input rate of 1.3 Mcps. Optimized filtering algorithms have been developed to preserve the spectroscopic capability of the system even in the very short processing times between events at these high rates. This Ultra-High Rate HPGe (UHRGe) spectroscopy system also operates at real time using a field-programmable gate array to perform spectral operations.
PDF
download
878987797
028-85220240
