STUDY ON THE PRECIPITATION OF Cu--RICH CLUSTERS IN THE RPV MODEL STEEL BY APT

Abstract

Reactor pressure vessel (RPV) is nonreplaceable component for the pressurized water reactor (PWR) in the nuclear power plants. RPVs are usually made of low alloy ferritic steels and A508-III steel is one type of these materials. After long-term service under the neutron irradiation, the ductile-to-brittle transition temperature (DBTT) of the RPV steel, which is the main parameter used to measure the degree of the embrittlement, will shift towards higher temperature. This phenomenon is termed irradiation-induced embrittlement, and it is a main factor to affect the operation safety and the lifetime of nuclear power plants. It is realized that the irradiation-induced embrittlement is mainly attributed to the precipitation of Cu-rich nanophases with a high number density. The precipitation process of Cu-rich nanophases can be well characterized by an atom probe tomography (APT) analysis for their size, composition and number density, and the Cu-rich nanophases obtained by the APT analysis are usually termed Cu-rich clusters. It is worthwhile to investigate the precipitation process of Cu-rich clusters by thermal aging for better understanding the mechanism of embrittlement. In order to accelerate the precipitation of Cu-rich clusters, experiment was performed by a RPV model steel containing higher Cu content than commercially available A508-III steel. RPV model steel was prepared by vacuum induction melting with higher content of Cu (0.6%, mass fraction). The specimens

Atomic Simulations for Packing Changes of Nano-Sized Cu Clusters Embedded in the Febulk on Heating

“…Brittle failure poses the greatest threat to the reactor. A large number of studies have shown that after long-term neutron irradiation at 288 • C, the impurity element Cu in the RPV steel will be precipitated as a Cu-rich nanometer phase, which is the main reason for the increase in tough-brittle transition temperature of RPV steel [9][10][11][12][13][14][15][16].…”