Researchers from University of Bristol (Bristol, United Kingdom) are investigating a small number of bulging stainless steel drums containing nuclear waste from Britain's nuclear reactors. According to the researchers, the bulges are most likely caused by corrosion of the 30- to 40-year-old metal-clad spent uranium, which is embedded in concrete inside the 500-L drums. When uranium corrodes, it can form either uranium oxide (UO2) or uranium hydride (UH3). UO2 forms relatively slowly when uranium reacts with oxygen or water. When water corrodes uranium, the reaction also releases hydrogen and forms UH3, which has the potential to cause fires. To see if this was occurring, the team created laboratory-scale models of the waste drums with matchstick-size bars of uranium embedded in concrete. The bars were corroded in wet, dry, and hydrogen-rich storage conditions. Using x-ray diffraction, the team identified the different corrosion products inside the models based on their deflection signatures. Three-dimensional representations of the models were created with tomography, enabling the team to measure corrosion rates. They found the UO2 barrier reduces the amount of corrosion from water as it grows thicker, but it does not prevent hydrogen from reaching the uranium. Source: American Institute of Physics, aip.org.
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