The influence of hydrogen peroxide and hydrogen on the corrosion of simulated spent nuclear fuel

Abstract

The synergistic influence between H₂O₂ and H₂ on the corrosion of SIMFUEL (simulated spent nuclear fuel) has been studied in solutions with and without added HCO₃⁻/CO₃²⁻. The response of the surface to increasing concentrations of added H₂O₂ was monitored by measuring the corrosion potential in either Ar or Ar/H₂-purged solutions. Using X-ray photoelectron spectroscopy it was shown that the extent of surface oxidation (U^V + U^VI content) was directly related to the corrosion potential. Variations in corrosion potential with time, redox conditions, HCO₃⁻/CO₃²⁻ concentration, and convective conditions showed that surface oxidation induced by H₂O₂ could be reversed by reaction with H₂, the latter reaction occurring dominantly on the noble metal particles in the SIMFUEL. For sufficiently large H₂O₂ concentrations, the influence of H₂ was overwhelmed and irreversible oxidation of the surface to U^VI occurred. Subsequently, corrosion was controlled by the chemical dissolution rate of this U^VI layer.