Optimization of a Quartz-Crystal Spectrometer Design for Analyzing K X-Rays From Pu and U

The ability to quickly and accurately quantify the Pu and U content within spent nuclear fuel is essential to nuclear forensics. The Pu/U ratio can be determined via non-destructive analysis (NDA) by detecting self-induced x-ray fluorescence (XRF) from the Pu and U in the fuel. However, during conventional spectroscopy, the characteristic x-ray peaks of interest are obscured by the Compton background and require extended exposure times. Quartz-crystal x-ray spectrometers allow x-rays of selected energies, obeying Bragg’s law for coherent scattering of incident photons, to be focused directly onto a detector. This provides a higher signal with less background by decreasing the possible Compton interaction in the detector. The spectrometer and collimator designs were optimized by simulating the system in MCNP. Also, the quartz crystal parameters were finalized by optimizing the probability of the diffraction of the xray energies of interest. The Pu and U XRF K-series lines range from 95 to 120 keV. Previous experiments investigating wavelength-dispersive spectrometers were performed at much lower energies (