The chemical durability of glass and graphite–glass composite doped with cesium oxide

• Published in: Journal of nuclear materials Vol. 432; no. 1-3; pp. 529 - 538
• Main Authors: Hamodi, Nasir H., Abram, Timothy J., Lowe, Tristan, Cernik, Robert J., López-Honorato, Eddie
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2013; Elsevier
• Subjects: Activation energy; Applied sciences; Cesium; Cesium oxides; Controled nuclear fusion plants; Dissolution; Durability; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Glass; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; Particulate composites; Surface chemistry; Borosilicates; Chemical stability; Cesium; Oxides; Carbon; Dissolution; Leaching; Nuclear reactor; Kinetic model; Boron; Valence; Graphite; Coated particle; Lixiviation; Silicon; Recycling; Microstructure; Alumina; Activation energy
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2012.09.010

The role of temperature in determining the chemical stability of a waste form, as well as its leach rate, is very complex. This is because the dissolution kinetics is dependent both on temperature and possibility of different rate-controlling mechanisms that appear at different temperature regions. The chemical durability of Alumina-Borosilicate Glass (ABG) and Glass–Graphite Composite (GGC), bearing Tristructural Isotropic (TRISO) fuel particles impregnated with cesium oxide, were compared using a static leach test. The purpose of this study is to examine the chemical durability of glass–graphite composite to encapsulate coated fuel particles, and as a possible alternative for recycling of irradiated graphite. The test was based on the ASTM C1220-98 methodology, where the leaching condition was set at a temperature varying from 298K to 363K for 28days. The release of cesium from ABG was in the permissible limit and followed the Arrhenius’s law of a surface controlled reaction; its activation energy (Ea) was 65.6±0.5kJ/mol. Similar values of Ea were obtained for Boron (64.3±0.5) and Silicon (69.6±0.5kJ/mol) as the main glass network formers. In contrast, the dissolution mechanism of cesium from GGC was a rapid release, with increasing temperature, and the activation energy of Cs (91.0±5kJ/mol) did not follow any model related to carbon kinetic dissolution in water. Microstructure analysis confirmed the formation of Crystobalite SiO2 as a gel layer and Cs+1 valence state on the ABG surface.