Quantification of Water-Content of Simulated Nuclear Waste Glasses Using Nuclear Reaction Measurements
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ABSTRACT Water content of glasses is an important factor in glass manufacture. In the case of slurryfed processing of waste glass melters, the water content of waste glasses may change the waste form properties significantly. A reliable, non-contact and quantitative measurement technique, with a spatial resolution of about 2-mm was used to determine the concentration of dissolved 9 water molecules in simulated nuclear waste glasses. The 1 F resonant reaction was used. The 9 9 'H (' F, (y)16O reaction requires a resonance energy that is available by use of a 6.471 MeV' F beam. A series of ten segments of slurry-fed, joule-heated, research-scale melter tests were conducted to determine the redox effects on processing of various feeds. Representative glass samples were collected at the middle of each segment. Their hydrogen contents were measured. The hydrogen content was correlated to the feed processing and redox of the glasses. INTRODUCTION Hydrogen and water are commonly found in several stages of generation, storage, and disposal of nuclear waste [1]. The presence of hydrogen can have significant effects on the electrical, mechanical, and chemical properties of some materials. Hydrogen is chemically versatile. As it has a valence of both +1 and -1, it can react with most elements. Additionally, hydrogen is many orders of magnitude more mobile than other common contaminants. Highenergy (MeV) ion beam techniques have been employed to measure hydrogen concentration profiles in a variety of materials, including glasses [2]. Recently, Lanford has presented the general considerations in hydrogen analysis and practical information on hydrogen profiling and data analysis in his excellent review [3]. All commercial glasses contain a certain amount of water in the form of hydroxyls (or hydrogen oxide). Hydroxyls [4] enter a glass structure and change the properties of a glass through the reaction: H20 (g) + -sSi-O-Si- 2-=Si-OH. Effects of water content on processing [5], electrical conductivity [6-8], mechanical strength [9-11], phase separation [ 12,13 ], structure [ 14-17], hygroscopicity [ 18], radiation effect [19], and thermal properties [20] of silica and silicate glasses have been extensively studied. The 'H (19F, otY)' 60 reaction used in this investigation requires a resonance energy that was available by use of a 6.471 MeV I9F beam. In this technique, the sample to be analyzed is bombarded with '9 F beam with energy at or above the resonant energy and the number of characteristic gamma rays produced in the target is measured with a scintillation detector. When the sample is bombarded with 9F at the resonance energy, the gamma-ray yield is proportional to hydrogen on the surface of the sample. When the sample is bombarded with '9F above the resonance energy, there are negligible reactions with the surface hydrogen because the energy is 353
Mat. Res. Soc. Symp. Proc. Vol. 556 © 1999 Materials Research Society
above the resonance energy. But, as the 19F ions penetrate the sample, they loose energy and reach the r
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