Beyond the classical kinetic model for chronic graphite oxidation by moisture in high temperature gas-cooled reactors

Validation of Wichner Predictive Model for Chronic Oxidation by Moisture of Nuclear Graphite

“…It is shown later in this report that calculations of oxidized layer profiles with the effective diffusivity corrected by the approximative relations from Eqs. (19) and (20) returned better results for 2114 but did not significantly improve the agreement between predictions and observations for IG-110.…”

“…The experimental setup used for chronic graphite oxidation by moisture is presented in detail elsewhere. 24,29 The main components ( Figure 5) are (1) the TAG furnace 16/18 (Setaram, France), a dual symmetrical thermogravimetric analyzer used for continuous weight loss measurements of graphite specimens in flowing H 2 O/H 2 /He at controlled temperatures; (2) the gas delivery manifold, which produces desired gas mixtures and controls the flow rates of each component (dry He, moist He, or 1% H 2 /He); (3) a controlled-temperature water bath for He humidification; (4) the hygrometer that measures the total gas pressure and the partial pressure of H 2 O just before the inlet of the TAG furnace; (5) a LabView application for data collection and control that commands the settings of mass flow controllers and records the corresponding flow rates, pressures, and humidity values; and (6) the mass spectrometer (Pfeiffer GSD 320) used occasionally for gas analysis of the effluent from the oxidation chamber in TAG.…”

“…o If needed, refine calculations by including Knudsen diffusivity D K and calculate global diffusivity coefficients from Eq. (19). In this study, that was done only for grades IG-110 and 2114. o Calculate detailed water and hydrogen concentration profiles in graphite below the surface, u (r) and v(r), from Eqs.…”

“…Partial results obtained during the progress of the project were presented at the annual DOE-Advanced Reactor Technologies (ART) program reviews 11,12,13,14,15 and professional conferences 16,17,18,19,20,21 and were published either as ORNL reports 22,23,24,25,26,27,28 or in open-access journals. 29 Soon after publication in 2018, the paper 29 on chronic oxidation kinetics of the four graphite grades had its first impact. A group of researchers from University of Michigan, University of Idaho, and Ohio State University used ORNL published data as the input kinetic information for a complex simulation of chronic oxidation by moisture in the He coolant of graphite fuel elements during long-term operation in a modular HTGR.…”

Study on 3D Pore Characteristics of Carbon Materials in HTGR by Micro-CT and HPMI Methods

“…Then the helium gas back to the pump and complete the cycle after two stage water-helium coolers and gas-water separator. There are studies that reported the oxidation behaviour of carbon material in HTGR, and some simulation models for the oxidation processes have been established [14][15][16]. Almost all of these studies have shown that the porosity and pore structure of the carbon materials have an important influence on the oxidation processes.…”