Measurement of Effective Diffusion Coefficients for Chloride Salts in Nonprotective Magnetite

Abstract

Abstract Measurement of diffusion coefficients for chloride salts in nonprotective magnetite have been performed. The nonprotective magnetite was produced by corroding carbon steel in a chloride solution at 260°C. The nonprotective magnetite was grown under compression in an isothermal capsule to simulate “denting” of steam generator tubes in pressurized water reactors. The effective diffusion coefficients were measured as a function of the dent size at temperatures from 54 to 260°C. The effective diffusion coefficient is described in terms of the porosity of the nonprotective magnetite, the sodium chloride bulk diffusion coefficient, and an empirically determined lithologic factor. The lithologic factor is a parameter that accounts for the resistance to diffusion from the porous structure. The lithologic factor was found to be a strong function of temperature from 54 to 149°C. The lithologic factor was not found to be a function of the dent size for the range of dent sizes investigated (0 to 140 µm).