Adrien Couet

Effect of Alloying Elements on Hydrogen Pickup in Zirconium Alloys

Although the optimization of zirconium-based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, we conducted a systematic study of the alloy effect on hydrogen pickup, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pickup fraction was accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure, and corrosion kinetics on hydrogen uptake. Two different techniques for measuring hydrogen concentrations were used: a destructive technique, vacuum hot extraction, and a non-destructive one, cold neutron prompt gamma activation analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy, but also during the corrosion process for a given alloy. These variations result from the process of charge balance during the corrosion reaction, such that the pickup of hydrogen decreases when the rate of electron transport or Manuscript received December 25, 2012; accepted for publication June 26, 2013; published online June 17, 2014. Dept. of Mechanical and Nuclear Engineering, Penn State Univ., University Park, PA 16802, United States of America (Corresponding author), e-mail: adrien.couet@gmail.com Dept. of Mechanical and Nuclear Engineering, Penn State Univ., University Park, PA 16802, United States of America. Westinghouse Electric Company LLC, Pittsburgh, PA 15235, United States of America. ASTM 17th International Symposium on Zirconium in the Nuclear Industry on February 3–7, 2013 in

Modeling Corrosion Kinetics of Zirconium Alloys in Loss-of-Coolant Accident (LOCA)

Correctly predicting the mechanical behavior of zirconium fuel cladding during a LOCA transient is critical for nuclear safety analysis as the fuel rod needs to maintain its coolable geometry throughout the LOCA sequence. A physically-based zirconium alloy corrosion model called the Coupled Current Charge Compensation (C4) is developed. The model calculates the coupling of oxygen, electron and hydrogen currents and predicts the oxide, oxygen-stabilized \( \alpha \)-Zr and prior-\( \beta \)-Zr layers kinetics as well as the oxygen concentration profiles during a LOCA scenario. The results obtained during isothermal conditions are compared to experimental data for validation. Future developments of the C4 model include an implementation into the nuclear performance code BISON, which currently does not provide a physical description of the oxygen and hydrogen concentration profiles in the cladding. Thanks to the C4 implementation into BISON, structural integrity of the fuel cladding following a LOCA event can be assessed.