Experimental investigation of corrosion of IG-110 graphite by steam

In the framework of a cooperation between the Japan Atomic Energy Research Institute (JAERI) and the Research Centre of Julien (KFA) experiments on the corrosion of the Japanese graphite IG-110 by water vapour were carried out. The temperature of the graphite samples and the water vapour partial pressure were kept constant at 1000°C/474 mbar. The total pressure in the test loop using helium as carrier gas was varied between 3 and 55 bar. Burn-off and pressure dependent reaction rates and density profiles in corroded samples were measured. As expected, the burn-off dependence of the reaction rate decreased with increasing pressure, while only a comparably low pressure dependence of the reaction rate was found. The latter indicates that the influence of the Knudsen diffusion is giveneven for the highest pressure. This finding is in fair agreement with the results of density profile measurements carried out at a couple of corroded samples, which also revealed a relatively small pressure dependence of the "penetration depth". Correlations for the caculation of reaction rates and the penetration depth are given

Korrosion von graphitischen Hochtemperaturreaktor-Werkstoffen mit Wasserdampf/Helium Mischungen im Druckbereich von 3-55 bar bei Temperaturen von 900-1150°C

In course of accident examination for High Temperature Reactors (HTR), experiments on the corrosion behavior of graphitie reactor materiale in steam have been performed at total pressures of 3-55bar and temperatures of 900-1150°C (1173-1423K); these experiments and their evaluation are documented here. Reactor materials examined are the structure graphite V483T2 and the tuel element matrices A3-27 and A3-3. In all experiments, the stearn partial pressure was 474rnbar (inert gas helium). The dependence of reaetion rates and density profiles on burn-off, total pressure and temperature has been examined. Experimental reaction rates depending on burn-off are fitted by theoretical curves, a procedure, which allows rate comparison for a weil defined burn-off. Comparing rates as a function of total pressure, V483T2 shows a linear dependence on 1/$\sqrt{p_{total}}$ whereas tor matrix materials a pressure independent rate was found for P$_{total}$4mm for A3-3