期刊
ACS APPLIED MATERIALS & INTERFACES
卷 8, 期 16, 页码 10562-10571出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.5b11323
关键词
nuclear fuel; dissolution; defects; oxygen vacancies; grain boundaries
资金
- European Atomic Energy Community's Seventh Framework Programme (FP7) [269903]
- University of Sheffield
- ECR Fellowship [(EP/N017374/1]
- EPSRC Nuclear FIRST Doctoral Training Centre [EP/G037140/1]
- EPSRC PACIFIC programme [EP/L018616/1]
- University of Sheffield Knowledge Transfer Account [EP/H500170/1]
- EPSRC
- REDUPP (REDucing Uncertainty in Performance Prediction) project
- Royal Academy of Engineering and the Nuclear Decommissioning Authority
- Engineering and Physical Sciences Research Council [1225666, EP/L018616/1] Funding Source: researchfish
- EPSRC [EP/L018616/1, EP/N017374/1] Funding Source: UKRI
The release of radionuclides from spent fuel in a geological disposal facility is controlled by the surface mediated dissolution of UO2 in groundwater. In this study we investigate the influence of reactive surface sites on the dissolution of a synthesized CeO2 analogue for UO2 fuel. Dissolution was performed on the following: CeO2 annealed at high temperature, which eliminated intrinsic surface defects (point defects and dislocations); CeO2-x, annealed in inert and reducing atmospheres to induce oxygen vacancy defects and on crushed CeO2 particles of different size fractions. BET surface area measurements were used as an indicator of reactive surface site concentration. Cerium stoichiometry, determined using X-ray Photoelectron Spectroscopy (XPS) and supported by X-ray Diffraction (XRD) analysis, was used to determine oxygen vacancy concentration. Upon dissolution in nitric acid medium at 90 degrees C, a quantifiable relationship was established between the concentration of high energy surface sites and CeO2 dissolution rate; the greater the proportion of intrinsic defects and oxygen vacancies, the higher the dissolution rate. Dissolution of oxygen vacancy-containing CeO2-x, gave rise to rates that were an order of magnitude greater than for CeO2 with fewer oxygen vacancies. While enhanced solubility of Ce3+ influenced the dissolution, it was shown that replacement of vacancy sites by oxygen significantly affected the dissolution mechanism due to changes in the lattice volume and strain upon dissolution and concurrent grain boundary decohesion. These results highlight the significant influence of defect sites and grain boundaries on the dissolution kinetics of UO2 fuel analogues and reduce uncertainty in the long term performance of spent fuel in geological disposal.
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