Chemical and Isotopic Characterization of Noble Metal Phase from Commercial UO₂ Fuel

Abstract

We report elemental and isotopic analysis for the noble metal fission product phase found in irradiated nuclear fuel. The noble metal phase was isolated from three commercial irradiated UO 2 fuels by chemically dissolving the UO 2 fuel matrix, leaving the noble metal phase as the undissolved residue. Macro amounts of this residue were dissolved using a KOH + KNO 3 fusion and then chemically separated into individual elements for analysis by mass spectrometry. Though the composition of this phase has been previously reported, this work is the most comprehensive chemical analysis of the isolated noble metal phase to date. We report both elemental and isotopic abundances of the five major components of the noble metal phase (Mo, Tc, Ru, Rh, Pd). In addition, we report a sixth element present in high quantities in this phase, tellurium. Tellurium appears to be an integral component of noble metal particles.

Distribution of metallic fission-product particles in the cladding liner of spent nuclear fuel

“…This study has also confirmed the observation by Pellegrini et al 36 that Te is a major fission product in these particles. The exact nature of the association of Te with the noble metal phase particles needs to be studied further.…”

“…Tellurium was consistently associated with the noble metal phase particles, and elemental analysis of a dissolved portion of the phase showed quantities around 5% of the particle. 36 These two studies (Pellegrini et al and this study) provide clear association of Te with the noble metal phase particles that had not been previously established in earlier studies. A line-scan across the particle showed evidence of chemical fractionation.…”

“…32 We have previously reported on the nature of the metallic particles from these fuels and aspects of their chemistry, including the variability of compositions in the 5-metal particles and the occurrence of Ag-Pd halides. 13,[33][34][35][36] In these earlier studies, we investigated metallic particles throughout the fuel; however, in this investigation, we concentrated on the FCI region and, in particular, the oxidized Zr metal liner nearest to the fuel.…”

Krypton-85 chronometry of spent nuclear fuel

“…This irradiation is substantially longer than typical in commercial reactor operations. Portions of this fuel were subsequently made available for study as 'Approved Testing Material 109' (henceforth, 'ATM-109'), which has also been characterized for various research purposes (e.g., Wolf et al, 2005;Buck et al, 2015;Pellegrini et al, 2019;Clark et al, 2020). Analyses of various subsamples of this material indicated radially averaged burnup in the range 61-78 GWd//ton (Wolf et al, 2005).…”

Reply on CC1

“…This irradiation is substantially longer than typical in commercial reactor operations. Portions of this fuel were subsequently made available for study as 'Approved Testing Material 109' (henceforth, 'ATM-109'), which has also been characterized for various research purposes (e.g., Wolf et al, 2005;Buck et al, 2015;Pellegrini et al, 2019;Clark et al, 2020). Analyses of various subsamples of this material indicated radially averaged burnup in the range 61-78 GWd//ton (Wolf et al, 2005).…”