Electron paramagnetic resonance (EPR) spectroscopy is an established nondestructive technique that has been applied in the nuclear field as an analytical method for <i>in situ</i> dosimetry. This technique is particularly useful for transition metals which can naturally exist as paramagnetic species, and they can be determined through exposure to a strong magnetic field generating unique resonance spectrum and through the interaction of the electron with the magnetic field of surrounding nuclei which results in a unique signal splitting known as hyperfine. This project evaluates EPR technology for non-destructive measurements of persistent fission products in environmental samples to supplement destructive analysis as a verification tool for safeguards. Proof-of-concept testing identified target analytes including stable isotopes of fission products ruthenium (Ru) and gadolinium (Gd), and the EPR spectroscopic parameters were optimized for their direct measurements and collection of the reference EPR spectral library initiated. It was observed that Ru in oxidation state +3 generates unique EPR signal resolved from common EPR-active environmental transition metals including iron, chromium, copper, and manganese. We have found that observation of Ru sorbed on zeolite matrix can be achieved not only in itself, but also in the presence of realistic concentrations of the environmental interferences. Demonstrated is the linear dependence of the EPR signal intensity on amount of Ru present in the sample enabling its quantification in these lab-developed samples. Similarly, Gd reliably produced concentration-dependent EPR signal in aqueous solutions. To-date experimental results will be presented including determination of Ru and Gd various reference soil matrices.
Year
2020
Abstract