Safety and economic challenges drive the search for new robust materials to enable more efficient and sustainable nuclear energy. Zirconium and silicon carbides and nitrides were recently proposed as fuel cladding materials, and their stability under irradiation needs to be fully understood. One of the concerns is water radiolysis leading to the formation of oxygen, hydrogen peroxide, and hydrogen, which are not favorable in nuclear reactor operation. In this work, we explore the effect of the surface composition on water radiolysis for zirconium carbides, nitrides, and silicon nitrides by evaluating hydrogen production under gamma irradiation. It was found that only the materials that have a significant amount of adsorbed water produce a detectable amount of hydrogen under 1 MGy of gamma irradiation. At the same time, in the presence of the water excess in slurries containing 20-90% of water, the difference between the studied materials was less pronounced. All ceramic powders have slightly increased hydrogen production under gamma irradiation in comparison with pure water. It was previously found that certain oxides, including zirconium oxide, can increase hydrogen yield, while others, like silicon oxide, do not affect hydrogen production. One of the possible suggested mechanisms requires hydroxyl groups present at the surface, and weekly bounded water available in close proximity to the surface. We demonstrate that the surface of zirconium carbide and nitride, as well as silicon nitride, have different amounts of oxygen present in the forms of water and oxides. The role of the oxide film and weakly bonded water on the surface of the ceramic powders in water radiolysis will be discussed.

Role of surface chemistry of several nitrides, carbides, and oxides on water radiolysis under ionizing radiation

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ACS Fall 2022

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