Electrochemical Study of Corrosion Phenomena in Zirconium Alloys
Abstract
Shadow corrosion of zirconium alloy fuel cladding in BWR environments, the phenomenon in which accelerated corrosion is experienced when the cladding surface is in close proximity to other metals, has become a potentially life-limiting issue for BWR fuel. Recent results from experimentation at MIT, Halden, and Studvik suggest that a galvanic coupling drives the phenomenon between the cladding and the adjacent material. However, the actual processes involved are not understood. One key parameter that would help in the understanding of the phenomenon would be a measurement of the actual corrosion current between fuel cladding and adjacent materials in the actual in-reactor environment. The limitations placed on the bum-up of uranium oxide fuel correlates to the amount of corrosion seen through a directly measurable oxide thickness on the waterside of the zirconium alloy cladding. This oxide corrosion product directly correlates to distance from structural components, leading to the effect commonly referred to as shadow corrosion. In recent experiments, Studvik determined that there are large ECP differences associated with Inconel and zirconium alloys that correlate to increased galvanic current density when the materials are coupled. In this thesis research, four electrode pairs were used to measure galvanic current densities in the irradiation environment: Pt-Pt, Zircaloy 2 (Zr-2)-Pt, Inconel (X-750)-Pt, and Zr- 2-X-75O. To determine the changes in the coolant water conductivity due to the presence of radiolysis products, electrochemical potential measurements of Pt-Pt coupled electrodes were analyzed. Finally, attempts to characterize the observed oxide behavior using measurements from Electrochemical Impedance Spectroscopy (EIS), also known as Alternating Current Impedance, were conducted.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2005
- Accession Number
- ADA447122
Entities
People
- Nicole M. Treeman
Organizations
- Massachusetts Institute of Technology