The corrosion rates of alloys that will be present in spent fuel waste packages are being measured to represent the generation rates of H2 in a breached package under a range of Eh-pH conditions. The H2 concentration is a crucial parameter in repository performance analyses because the presence of even small amounts of H2 in a breached waste container can significantly decrease the oxidative-dissolution rate of directly-disposed spent UO2 fuel. Potentiostatic tests are being conducted in pH 4, 7, and 10 buffer solutions spiked with NaCl at several potentials that span the ranges of redox and chemical conditions that could occur in a breached waste package. The corrosion currents are monitored as the alloys corrode and changes in the electrical properties of the metal surfaces are measured using electrochemical impedance spectroscopy. Results of tests with 316L stainless steel, Zircaloy-4, and 4320 low alloy carbon steel conducted at several voltages in pH 10 solutions with added NaCl are presented as examples. The dependencies of alloy corrosion rates on these variables and the sensitivity of the fuel dissolution rate are discussed.

Subject
Electrochemical impedance spectroscopy, Steel surfaces, Materials, Voltage, Hydrogen concentration, Corrosion rate, Cathodic current, Anode surfaces, Current measurements, Corrosion modeling, Steel, Carbon steel, Wastes
Keywords:
steel corrosion, potentiostatic tests, H2 generation
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2021
Association for Materials Protection and Performance (AMPP)
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