Evolution of cations speciation during the initial leaching stage of alkali-borosilicate-glasses
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.39
Evolution of cations speciation during the initial leaching stage of alkali-borosilicate-glasses Osama M. Farid1, M.I. Ojovan2, R.O. Abdel Rahman3* 1
Reactors Department, Nuclear Research Center, Atomic Energy Authority of Egypt, P.O. 13759, Inshas, Cairo, Egypt; [email protected] 2
Department of Materials Science and Engineering, The University of Sheffield, UK; [email protected] 3*
Hot Laboratory Center, Atomic Energy Authority of Egypt, P.O. 13759, Inshas, Cairo, Egypt; [email protected]
Abstract:
Alkali-borosilicate glasses (ABS) are used as host immobilization matrices for different radioactive waste streams and are characterized by their ability to incorporate a wide variety of metal oxides with respectively high waste loadings. The vitreous wasteform is also characterized by very good physical and chemical durability. The durability of three ABS compositions were analyzed by investigating their leaching behavior using the MCC1 test protocol and these data were used to investigate the waste components retention in the altered layer and the evolution of the interfacial water composition during the test. The results indicated that the Mg species evolution is exceptional with respect to other alkaline elements and dependent on glass matrix composition and leaching progress, while transition elements speciation is fairly constant throughout leaching process and independent on glass compositions. Si and B species are changing during leaching process and are affected by waste composition. For modified wasteform sample, evolution of Mg, Si and B species is respectively constant, whereas at highest waste loading, these elements have fairly constant speciation evolution within the first 2 weeks of leaching.
INTRODUCTION: The long-term safety of nuclear/radioactive waste disposal sites depends on the integrated performance of passive engineered barriers and natural barriers to control radionuclides releases from the disposal facility [1, 2]. To assess the long –term performance of the disposal practice, the features, events, and processes (FEP) that may
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occur and affect the safety of the practice are used to build reference and alternative scenarios [1, 2]. The developed scenarios are used to model the evolution of the disposal performance [3]. Natural evolution scenario is usually considered as the reference scenario for geological disposal, it describes the projected state of the natural and engineered barriers due to the presence of most probable features, events and process [46]. In natural evolution scenario, the performance of the waste package could be compromised due to different chemical, thermal, mechanical, hydraulic, biological, and radiological processes that take place over thousands of yea
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