Influence of Ammonia on the Corrosion Behavior of a Zr–Sn–Nb Alloy in High Temperature Water

Abstract

Corrosion behaviors, microstructures of oxide films, and hydrogen absorptions of a Chinese domestic Zr alloy in 6.7 × 10−3 mol/L ammonia solution and 2.9 × 10−4 mol/L LiOH+9.3 × 10−2 mol/L H3BO3 solution at 360 °C, 18.6 MPa were studied. Weight gains, oxide film thicknesses, and hydrogen absorptions showed that the corrosion rate in the ammonia solution is a little higher than that in the boron–lithium solution. There is no significant difference in the microstructure and crystalline structure between the oxide films formed in the two types of solutions. The element distributions along the depth direction of the oxide films showed the existence of nitrogen in the oxide film formed in ammonia solution. Moreover, nitrogen was found to be segregated in local areas in a range of about 2 μm from the oxide/metal interface. The corrosion behavior of the Chinese domestic Zr alloy in 360 °C aqueous solution shows no difference with other Zr alloys.

Effect of Boron Content in LiOH Solutions on the Corrosion Behavior of Zr-Sn-Nb Alloy

“…At present, most of the primary coolant of PWRs is boron-lithium type, and the irradiation decomposition of water is suppressed by dissolved hydrogen [6]. Under this condition, Zr-Sn-Nb alloy maintains good corrosion resistance.…”