Deposition of volatilized ruthenium on stainless steels

The volatilization of Ru in nuclear fuel processing and waste management operations gives rise to a number of potential problems, many of which relate to the subsequent deposition of volatilized material in downstream plant and pipework. As well as the physical effects of bulk deposites, this can pose radiological hazards on account of the radioisotope exp 106 Ru that is present in appreciable quantities in fission products at short and moderate cooling times. Volatile Ru deposition at temperatures of 150 deg C and above, under the conditions occurring in nuclear processing plants, produces the crystalline dioxide RuO sub 2 , and no bonding with the steel surfaces occurs. Deposits were prepared on Type 321 and Type 304L stainless steel substrates under conditions likely to occur in nuclear processing plants, particularly in waste calcination and vitrification, where the problem is most acute. The deposits were formed on the substrates at 150 deg C from Ru generated by calcination of a Ru(NO) (III) solution in nitric acid. The deposits were examined by SEM, microscopy, and X-ray analysis, including diffraction patterns and photoelectron spectra.