Study of simulated HLW-glass leaching behavior under low oxygen repository condition
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Study of simulated HLW-glass leaching behavior under low oxygen repository condition Zhang Hua* and Luo Shanggeng Radiochemistry Department, China Institute of Atomic Energy, P.O.Box 275(93), Beijing, 102413, P.R.China ABSTRACT Many countries have recognized vitrification as the suitable solidification method for conditioning high level radioactive waste before they are isolated from biosphere in geologic disposal. This paper studies the leaching behavior of a simulated HLW-glass (90Nd/10) under low oxygen repository condition during 1.5 years. The leaching results showed that the glass was corroded less under low oxygen condition than under ambient atmosphere. XRD analyses showed some little diffraction peak appeared on the leached glass surface at 150°C. At the same time, no diffraction peak appeared on the leached glass surface at 90°C. The secondary products formed on the surface of the leached glass contained mainly Si, Al, Ca and Fe. INTRODUCTION Vitrification has been widely accepted as a feasible and credible option for conditioning high level radioactive wastes. The glass package will be disposed in a deep geological formation and isolated from human biosphere. Studying the dissolution behavior of the glass and the contained nuclides and making the safe assessment are the important issues in high level radioactive waste management. Recently, many countries, such as U.S.A, France, Germany, Belgium and Japan [1, 2] are working on the related research, which includes the siting of geologic repositories and research programmes in the underground research laboratories, etc.. In China, the repository site is under selection in Gansu province. This paper presents a set of experiments to investigate the leaching behavior of simulated HLW-glass (90Nd/10) under simulated low oxygen repository conditions. EXPERIMENTAL According to leaching test method MCC-1[3], experiments were carried out in a low oxygen glove box，in which the Ar concentration was higher than 99.999% and the O2 concentration was less than 1 ppm. The leachants were deionized water and simulated ground water. The leachates were analyzed by a TJA Advantage ICP-AES and a VG Plasma Quad II Plus ICP-MS. The leached glass specimens surface were investigated by a Rigaku K/max-RB X-Ray diffraction meter (XRD) using Cu Kα, (λ= 1.54 nm) radiation. The microstructure of the leached glass specimen surface was analyzed by a LEO-1450 SEM (scanning electron microscope) with KEVEX Sigma XEDS (X-Ray energy dispersive system). *Corresponding author: Tel: +86-010-69357445; Fax: +86-010-69358509 E-mail: [email protected]
The tested glasses were fabricated according to the selected formulation. First, the chemicals were put into the mortar, then triturated and mixed equably before they were put into crucibles. The crucibles were put into an electric furnace, in which the temperature was slowly risen up to 1150°C and kept at this temperature for 3h. After that, the crucibles were taken out to pour the melted glass into the graphite mould. Then, the molten glasses were
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