Abstract
To reflect potential conditions in a geological disposal facility, uranium was encapsulated in grout and submersed in de-ionised water for time periods between 2–47 weeks. Synchrotron X-ray Powder Diffraction and X-ray Tomography were used to identify the dominant corrosion products and measure their dimensions. Uranium dioxide was observed as the dominant corrosion product and time dependent thickness measurements were used to calculate oxidation rates. The effectiveness of physical and chemical grout properties to uranium corrosion and mobilisation is discussed and Inductively Coupled Plasma Mass Spectrometry was used to measure 238U(aq) content in the residual water of several samples.
Highlights
Uranium metal is a significant contributor to Intermediate Level nuclear Waste (ILW) at Sellafield, UK
In the following experiment we address this problem by performing an in-situ study of uranium corrosion in grout under full water submersion conditions, in an attempt to reflect the main features of a saturated Geological Disposal Facility (GDF)
Each sample was analysed on the I12, Joint Engineering, Environment and Processing (JEEP) beam line, at the Diamond Light Source (DLS) over two separate beam times
Summary
Uranium metal is a significant contributor to Intermediate Level nuclear Waste (ILW) at Sellafield, UK. The uranium oxidation rate was observed as initially rapid, but decreased over time, and near 50 weeks plateaued at a rate believed to reflect the steady state exchange of gases through the near-matured grout These findings are important because Equation 1 yields hydrogen which can potentially become trapped in the grout pores and if concentrations are allowed to increase over long periods of time, uranium hydride (UH3) may form. This compound is a black powder which has been known to spontaneously ignite in oxidising conditions[6,7] and, in addition to hydrogen gas, significantly increases the risk for future transportation, storage and disposal of the ILW containers. These processes are complex and dependent on a multitude of environmental conditions, each of which must be investigated
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