Sorption isosteres and isotherms of silver on NBG-17 graphite

• Published in: Journal of nuclear materials 2021-12, Vol.557 (C), p.153264, Article 153264
• Main Authors: Walton, Kyle L., Jacobson, Nathan S., Kowalski, Benjamin A., Brockman, John D., Loyalka, Sudarshan K.
• Format: Article
• Language: English
• Subjects: Adsorption; Effusion; Fission products; Graphite; Heat of adsorption; High temperature gas cooled reactors; Isotherms; Mechanistic source term; Metal adsorption; Silver; Surface chemistry; Very high temperature reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2021.153264

•Adsorption isosteres of Ag on NBG-17 were measured from 23.2 to 90.4 mmolAg (kgC)−1.•Heats of adsorption of Ag on NBG-17 ranged from 255.4 to 337.6 kJ mol−1.•Adsorption isotherms of Ag on NBG-17 were determined from 1050 to 1175 K.•Temperature-dependent forms of the Langmuir and Freundlich (IAEA) were fitted to isotherm data. Adsorption data and isotherms of various fission products on graphite are needed for high-temperature gas-cooled reactor mechanistic source term estimations. Measurements of such data for NBG-17 graphite powders, preloaded with Ag, are described. The samples were desorbed in a Knudsen-effusion mass-spectrometer. Data was sorted into adsorption isosteres for surface loadings from 23.2 to 90.4 mmolAg (kgC)−1. Straight-line fits to the Clausius-Clapeyron representation of isosteres gave the heats of adsorption as function of surface loading. Adsorption isosteres were further refined to determine adsorption isotherms from 1050 to 1175 K. Langmuir, IAEA-Freundlich, and IAEA isotherm models were fitted to the isotherm data. The IAEA and Langmuir isotherms provided a better fit than the IAEA Freundlich isotherm.