Abstract
The corrosion reaction of unirradiated uranium with deuterated liquid water under an argon (Ar) overpressure was investigated. Two samples were examined at two temperatures (55 °C and 70 °C) under an argon atmosphere and contained conditions. The rate of corrosion was derived by monitoring the pressure changes in the cell as a function of time (ascribed to D2 generation from U-corrosion). Post-corrosion examination was conducted using FIB and XRD. Measurements of water pH were made immediately after the experiments were stopped. From the analyses, it was concluded uranium-deuteride (UD3) was formed in the reaction products as part of the U‑D2O(l) -Ar(g) reaction. This result confirms the formation of uranium hydride/deuteride as part of the uranium-liquid water reaction in an enclosed environment, where deuteride forms through the reaction of U with oxidation-generated D2. From reaction rate behaviour combined with post-reaction surface/interface analysis, it is suggested that after a gas ‘threshold’ pressure limit is reached (~0.5 bar) UD3 formation is facilitated, leading to volume expansion and generation of stress in the overlying oxide. Breakage of this oxide would lead to direct exposure of UD3 and U to aqueous oxidation, leading to reaction rate enhancement.
Highlights
In the UK, the total amount of radioactive waste is estimated at approximately 4.77 million m3 as summarized by the Nuclear Decommissioning Authority (NDA) on April 1st, 2016 [1]
The long-term reaction of the U-D2O(l)-Ar ternary system was examined at 55 C and 70 C under enclosed/contained conditions
A very complex morphology of different texture than that of UO2 could be observed on some of the cross-sectional faces of the samples (Fig. 2). These findings strongly imply that UO2 is not the only phase forming in the reaction products, with uranium hydride likely to be produced
Summary
In the UK, the total amount of radioactive waste is estimated at approximately 4.77 million m3 as summarized by the Nuclear Decommissioning Authority (NDA) on April 1st, 2016 [1]. This continuous increasing stock of waste material, which requires safe handling, treatment, storage and permanent disposal, presents one of the most serious technical challenges for the nuclear industry. Intermediate level waste (ILW) represent ~6% of the total stock in the UK, the majority of which are currently interim stored in A. Banos et al / Journal of Nuclear Materials 535 (2020) 152178 silos and to a lower extent in the ponds [2]. The potential for thermal transients, thermal excursions and even pyrophoric reactions owing to the unstable nature of bulk UH3 under sudden exposure to air and other oxidants raises serious safety and technical concerns for the industry
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
