Chapter 9 - Ni-Based Alloys for Reactor Internals and Steam Generator Applications

Abstract

Nickel alloys have been used extensively throughout the nuclear industry because of their durability and resistance to corrosion and mechanical degradation at high temperatures. When nuclear plants were first constructed, however, the performance of Ni alloys over the long periods of nuclear reactor operation was not fully known. Over the past 50–60years, improved Ni alloys have been developed to better suit the particular operating conditions in nuclear power plants. For Ni-alloy components used in steam generators (SGs), pressure vessels, fuel assemblies, and other reactor core internals, improvements have been primarily directed at mitigating stress corrosion cracking. In the reactor core, there is the additional effect of neutron irradiation on Ni-alloy performance that has to be considered. The most important aspect of in-core behavior of Ni alloys is the fact that transmutation of the main natural isotope, 58Ni, to 59Ni results in enhanced radiation-induced degradation that is unique to Ni among common engineering alloys.