Year
2012
Abstract
High Resolution X-ray (hiRX) is a new analytical method being developed for detection of actinide elements associated with spent fuel. The use of doubly curved crystals (DCC) in hiRX offers a unique combination of high energy resolution and sensitivity which provides great potential for safeguards applications. The DCCs are utilized on both the excitation and collection sides of the instrument. This affords both monochromatic excitation and detection resulting in high sensitivity single element detection. The prototype instrument uses the RhKa line at 20.214 keV for excitation. When this monochromatic excitation is combined with the DCC used to collect the X-ray fluorescence for the Pu analyte, in this case the PuLa line at 14.279 keV, the resulting spectra exhibit a single peak with near zero background. The prototype instrument has achieved a limit-of-detection of about 130 pg with direct excitation of dried residues of aqueous Pu solutions. This detection limit is well below the levels achieved with conventional methods of Pu assay. When the hiRX spectrum is compared with a conventional energy dispersive X-ray fluorescence (EDXRF) spectrum, there is a significant reduction in background. This background reduction is attributed to several factors based on the monochromatic features of the instrument: 1) monochromatic excitation reduces the scatter from the sample; 2) monochromatic detection filters out the intrinsic radiation from the sample, 3) intense peaks from other elements are eliminated from detection. Each one of these features enhances the sensitivity of hiRX and provides a high fidelity signal for detection. This paper will present new results on the application of hiRX to typical spent fuel elemental composition using a synthetic cold surrogate solution containing 50elements along with a high level of uranium. These results offer insight into the advantages of hiRX for sensitive Pu assay and the eventual application to a real spent fuel samples.