Prediction of the Lifetime Integrity of a Nuclear Waste Container Material Based on Thermal Stability Studies

Abstract

The kinetics of precipitation in C-22 alloy (UNS N06022) was estimated through isothermal aging experiments at temperatures ranging from 427°C to 800°C for times up to 40,000 h. The phases that formed, at least after the longer aging times, were identified by transmission electron microscopy (TEM).Aged samples were also examined using scanning electron microscopy (SEM) to determine when precipitation began on grain boundaries, completely covered grain boundaries, and began forming within the grains. This data was used to evaluate the kinetics of precipitation at lower temperatures using a simple exponential temperature dependende. The corrosion resistance of aged samples was investigated using the ASTM Specification G28B technique. The time to cause a significant increase in corrosion rate was also determined as a function of temperature and was fit to an exponential temperature dependence. Preliminary results indicate that C-22 alloy base metal would remain a highly corrosion resistant, single-phase material for greater than 10,000 years at temperatures below approximately 300°C.

Corrosion-resistant alloy testing and selection for oil and gas production

“…Lehman and Kosel [68] and Abd-Elhady and Sargent [69] showed that for model Ni 2 Cr intermetallic alloys containing different concentrations of P, the ordering reactions were accelerated by the presence of higher P. The ordering reactions have been shown to occur in other Ni–Cr–Mo alloys [70,71] and they occur very slowly in annealed alloys at temperatures below 500°C [72,73]. Some Ni–Cr–Mo alloys are aged at close to 700°C to form ordered Ni 2 Cr type phase in order to strengthen the alloy through heat treatment [74,75].…”