Sorption isosteres and isotherms of silver on NBG-17 graphite

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. Finally, the IAEA and Langmuir isotherms provided a better fit than the IAEA Freundlich isotherm.