The Use of Self-Induced XRF to Quantify the Pu Content in MOX Spent Nuclear Fuel

The development of techniques for the accurate quantification of the plutonium content in spent nuclear fuel would provide significant advances for shipper/receiver differences and for input accountability at reprocessing facilities. Several techniques have been studied previously for achieving this goal but these have met with limited success. Due to the radioactive nature of spent fuel, decay energy is being deposited in the fuel at a relatively constant rate. That decay energy leads to self-induced x-ray fluorescence of the uranium and plutonium atoms in the fuel. These resulting x-rays are then emitted by the fuel rod and can be measured in an appropriately designed and implemented instrument. The presence of uranium x-rays has been observed on numerous occasions; however, due to its dilute nature in the spent fuel and the presence of a large background, the plutonium x-rays have only been observed in a small number of experiments and generally with fuel containing very large loadings of plutonium. In this work, a feasibility study was conducted using both Monte Carlo simulations and measurements of PWR spent fuel rods at Oak Ridge National Laboratory as part of the Coupled End-to-End (CETE) demonstration. This feasibility study demonstrated the measurability of the plutonium x-rays for PWR spent fuel with burnups ranging from 35 to 70 GWd/MTU and the potential application of this technique as a quantitative assay tool.