Stress Corrosion Cracking Behavior of Commercial Zr702 in Boiling Nitric Acid Solutions for Spent Nuclear Fuel Reprocessing

The stress corrosion cracking (SCC) and its susceptibility (I-SCC) of commercial Zr702 applied for spent nuclear fuel reprocessing industry was investigated in boiling nitric acid. Stress-strain curves of Zr702 in boiling nitric acid with strain rate of 10(-5) s(-1) were obtained using independent designed slow strain rate tension (SSRT) system. Microscopic characterizations as well as numerical analysis were carried out to quantify the SCC behavior of Zr702. Results reveal that the I-SCC of Zr702 obviously increases from 5% to 26.67% with the increase in HNO3 concentration. The sharp decline in the mechanical properties of commercial Zr702 in boiling HNO3 solutions is attributed to cleavage fracture on surfaces of specimen, and the depth of the cleavage cracks increases with the growing HNO3 concentration. Finally, a model and an equation to predict the SCC behavior of commercial Zr702 in boiling HNO3 solutions was proposed. The quantitative relationship among HNO3 concentration, I-SCC, fracture stress (sigma SCC) and cleavage crack depth (d(cc)) can be described and predicted using a high-order regression equation.