Transport through carbon steel of hydrogen produced by flow-accelerated corrosion

Abstract

Atomic hydrogen is produced as a by-product when a ferrous metal surface is exposed to water at a high temperature at a rate corresponding to the rate of corrosion. In de-aerated conditions, the hydrogen atoms permeate through the steel and combine into pairs to form molecular hydrogen at the opposite surface. Because of rapid diffusion of hydrogen through ferrite steels at the temperature of interest, the total rate of hydrogen emission from the steel is a measurement of the instantaneous corrosion rate. The Hydrogen Effusion Probe (HEP) has been developed for an online monitor of Flow Accelerated Corrosion (FAC) by measuring the generated through-wall hydrogen. This study was carried out to investigate the transport of hydrogen through steel to obtain a fundamental understanding of the through-wall hydrogen behaviour. HEPs have been installed on a feeder pipe in the Point Lepreau Generating Station (PLGS), on a boiler wall in the Coleson Cove Generating Station (CC), and in a test loop at the Centre Nuclear Energy Research (CNER) laboratory. Data from PLGS, CC and the experiments indicate that the HEP is sensitive and responsive to changes in FAC rate, and can provide an on-line monitor of FAC.