Interaction of ruthenium tetroxide with surfaces of nuclear reactor containment building

During a severe nuclear accident, different fission products will be released from the nuclear fuel and some of them may eventually reach the containment building. Ruthenium is considered to be an important fission product due to the possible formation of volatile oxides. Radiotoxicity and chemical toxicity of the volatile ruthenium compounds present a considerable hazard during a severe nuclear accident.

In this work, experiments regarding behavior of ruthenium tetroxide in the reactor containment were performed. The interactions of ruthenium tetroxide (RuO₄) with zinc, copper, aluminum and epoxy paint in dry and humid atmosphere were examined. SEM/EDX (scanning electron microscope/energy-dispersive X-ray spectroscopy), XPS (X-ray photoelectron spectroscopy) and EXAFS (extended X-ray absorption fine structure) techniques were used to identify the chemical composition of the deposits formed after the interaction of RuO₄ with the different materials. Additionally, distribution of ruthenium between different metals was examined.

Interaction of RuO₄ with the studied samples led to formation of dark, ruthenium-rich deposits. Examination of these deposits showed different chemical speciation of ruthenium on the surface when compared to the deeper layers of deposits. Interaction of RuO₄ with zinc, copper and aluminum resulted to different amounts of the deposited ruthenium on the metals.