A. Hoover, W. S. Charlton, M.L. Fensin, A. Rajasingam, C. Rudy, S. Saavedra, A. Stafford, D. Strohmeyer, S. Tobin, “Measurement of Plutonium in Spent Nuclear Fuel by Self-Induced X-ray Fluorescence”, 2009 Annual Meeting of the Institute of Nuclear Materials Management, Tucson, AZ, July 12-15, 2009.
Direct measurement of the plutonium content in spent nuclear fuel is a challenging problem in non-destructive assay. The very high gamma-ray flux from fission product isotopes overwhelms the weaker gamma-ray emissions from plutonium and uranium, making passive gamma-ray measurements impossible. However, the intense fission product radiation is effective at excitingplutonium and uranium atoms, resulting in subsequent fluorescence X-ray emission. K-shell X-rays in the 100 keV energy range can escape the fuel and cladding, providing a direct signal from uranium and plutonium that can be measured with a standard germanium detector. The measured plutonium to uranium elemental ratio can be used to compute the plutoniumcontent of the fuel. The technique can potentially provide a passive, non-destructive assay tool for determining plutonium content in spent fuel. In this paper, we discuss recent non-destructive measurements of plutonium X-ray fluorescence (XRF) signatures from pressurized water reactor spent fuel rods. We also discuss how emerging new technologies, like very-high energy resolution microcalorimeter detectors, might be applied to XRF measurements.