Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Abstract

In light water reactors, components made of nickel-base alloys are susceptible to environmentally assisted cracking. This report summarizes the crack growth rate results and related metallography for field and laboratory-procured Alloy 600 and its weld alloys tested in pressurized water reactor (PWR) environments. The report also presents crack growth rate (CGR) results for a shielded-metal-arc weld of Alloy 182 in a simulated PWR environment as a function of temperature between 290°C and 350°C. These data were used to determine the activation energy for crack growth in Alloy 182 welds. The tests were performed by measuring the changes in the stress corrosion CGR as the temperatures were varied during the test. The difference in electrochemical potential between the specimen and the Ni/NiO line was maintained constant at each temperature by adjusting the hydrogen overpressure on the water supply tank. The CGR data as a function of temperature yielded activation energies of 252 kJ/mol for a double-J weld and 189 kJ/mol for a deep-groove weld. These values are in good agreement with the data reported in the literature. The data reported here and those in the literature suggest that the average activation energy for Alloy 182 welds is on the order of 220-230 kJ/mol, higher than the 130 kJ/mol commonly used for Alloy 600. The consequences of using a larger value of activation energy for SCC CGR data analysis are discussed.iv This page is intentionally left blank. Foreword vThis report presents crack growth rate (CGR) data and the results of the corresponding fracture surface and metallographic examinations from cyclic loading and primary water stress-corrosion cracking (PWSCC) tests of two nickel-base Alloy 182 (A182) weldments. These weldments are typical of those used in vessel penetrations and piping butt welds in nuclear power plants. The effect of crack orientation with respect to dendrite orientation is the most significant variable investigated in this study. However, this report also compiles data from other laboratories that describe the effects of material composition, loading characteristics, and chemistry of the aqueous environment. The PWSCC growth rates described for the A182 specimens in the report are comparable to the CGR that characterize the performance of Alloy 600 (A600).This report is one of a series of reports documenting the results of CGR testing in vessel head penetration materials. This report focuses on the Alloy 82 (A82) and A182 weld metals. This report also presents results from tests of the A600 base metal. The researchers tested (1) a laboratory-fabricated, shieldedmetal-arc deposit of A182; (2) a weldment sample from the J-groove weld of a control rod drive mechanism nozzle from the Davis-Besse Nuclear Power Plant; and (3) a hot leg nozzle-to-safe end weld from the Virgil C. Summer Nuclear Station.

Robustness of RISMC Insights under Alternative Aleatory/Epistemic Uncertainty Classifications: Draft Report under the Risk-Informed Safety Margin Characterization (RISMC) Pathway of the DOE Light Water Reactor Sustainability Program

“…In recent research, the fitting constant (ε) is defined as log-normally distributed with a median value of approximately 8×10 -13 [31]. For this demonstration, the median value is set to 8×10 -13 and the 5 th percentile of the lognormal distribution was set to 40% of the median value.…”

Physics-Based Stress Corrosion Cracking Component Reliability Model cast in an R7-Compatible Cumulative Damage Framework

“…There are numerous estimates of the fitting constant for growth amplitude ε in the literature. In recent research, the fitting constant is assessed to be log-normally distributed with a median value of approximately 8E-13 [19]. For our model, the fitting constant was bracketed at the 5th and 95th percentiles of the lognormal distribution.…”

Kohonen mapping of the crack growth under fatigue loading conditions of stainless steels in BWR environments and of nickel alloys in PWR environments

“…Crack growth rates were collected from tables of data published in internal reports generated by Argonne National Laboratory [1][2][3].…”

“…

Crack Growth Rates and Metallographic Examinations of Alloy 600 and Alloy 82/182 from Field Components and Laboratory Materials Tested in PWR Environments, NUREG/CR-6964, May 2008]. The data collected were measured on austenitic stainless steels in BWR (boiling water reactor) environments and on nickel alloys in PWR (pressurized water reactor) environments.

…”