Probabilistic Failure Analysis of Austenitic Nuclear Pipelines against Stress Corrosion Cracking

2005 ◽  
Vol 219 (7) ◽  
pp. 607-624 ◽  
Author(s):  
C Priya ◽  
K. B. Rao ◽  
M. B. Anoop ◽  
N Lakshmanan ◽  
V Gopika ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Degradation Mechanism ◽  
Failure Criteria ◽  
Initial Crack ◽  
Corrosion Cracking ◽  
Austenitic Steels ◽  
Failure Assessment ◽  
Degree Of Sensitization ◽  
Failure Probabilities

Stress corrosion cracking (SCC) is an important degradation mechanism to be considered for failure assessment of nuclear piping components made of austenitic steels. In this paper, an attempt has been made to compute the failure probabilities of a piping component against SCC with time using Monte Carlo simulation (MCS) technique. The initiation and propagation stages of stress corrosion cracks are modelled using the general methodology recommended in PRAISE modified by using the recommendations given by ASM for more rational modelling of stress field around cracks for estimating their growth with time. Degree of sensitization, applied stress, time to initiation of SCC, initial crack length, and initiation crack growth velocity are considered as random variables. An attempt has been made to study the stochastic propagation of stress corrosion cracks with time, using MCS technique. The trend of the distribution of crack depths at the initial stages obtained from simulation are compared and is found to be in satisfactory agreement with the relevant experimental observations reported in the literature. The failure probabilities are computed using two different failure criteria, namely (a) based on net-section stress and detectable leak rate as recommended in PRAISE and (b) based on R6 approach (using R6-option 1 curve as the failure assessment diagram). The procedure presented in the paper is general and the usefulness of the same is demonstrated through an example problem.

Strategies for Treating Weld Residual Stresses in Probabilistic Fracture Mechanics Codes

2011 ◽  
Author(s):  
Frederick W. Brust ◽  
R. E. Kurth ◽  
D. J. Shim ◽  
David Rudland
Keyword(s):  
Fracture Mechanics ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Degradation Mechanism ◽  
Welding Process ◽  
Corrosion Cracking ◽  
Uncertainty Sources

Risk based treatment of degradation and fracture in nuclear power plants has emerged as an important topic in recent years. One degradation mechanism of concern is stress corrosion cracking. Stress corrosion cracking is strongly driven by the weld residual stresses (WRS) which develop in nozzles and piping from the welding process. The weld residual stresses can have a large uncertainty associated with them. This uncertainty is caused by many sources including material property variations of base and welds metal, weld sequencing, weld repairs, weld process method, and heat inputs. Moreover, often mitigation procedures are used to correct a problem in an existing plant, which also leads to uncertainty in the WRS fields. The WRS fields are often input to probabilistic codes from weld modeling analyses. Thus another source of uncertainty is represented by the accuracy of the predictions compared with a limited set of measurements. Within the framework of a probabilistic degradation and fracture mechanics code these uncertainties must all be accounted for properly. Here we summarize several possibilities for properly accounting for the uncertainty inherent in the WRS fields. Several examples are shown which illustrate ranges where these treatments work well and ranges where improvement is needed. In addition, we propose a new method for consideration. This method consists of including the uncertainty sources within the WRS fields and tabulating them within tables which are then sampled during the probabilistic realization. Several variations of this process are also discussed. Several examples illustrating the procedures are presented.

Effect of Long-Term Service Exposure on the Localized Corrosion and Stress Corrosion Cracking Susceptibility of Type 347 Stainless Steel

CORROSION ◽  
10.5006/2612 ◽  
2017 ◽  
Vol 74 (3) ◽  
pp. 350-361 ◽  
Author(s):  
K. Ravindranath ◽  
N. Tanoli ◽  
B. Al-Wakaa
Keyword(s):  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Localized Corrosion ◽  
X Ray Diffraction ◽  
Degree Of Sensitization ◽  
Corrosion Susceptibility ◽  
Service Exposure

The paper presents the results of a study conducted on the effects of long-term service exposure of Type 347 stainless steel (SS) on the microstructure and corrosion susceptibility. The material subjected to the study was in service in a petroleum refinery as heater tube at 620°C for 31 years. The microscopic and x-ray diffraction studies of the service-exposed specimen revealed the precipitation of chromium-rich carbides along the grain boundaries. The microstructural changes that occurred as a result of service exposure affected the ductility and toughness of the alloy. The sensitization of the alloy was assessed by scanning electron microscopy and double loop electrochemical potentiodynamic reactivation. The studies have indicated some degree of sensitization in the alloy. The service exposure resulted in a marginal increase in the susceptibility of Type 347 SS to pitting in environments containing NaCl and NaCl + H2S. Environments such as H2SO4 and K2S4O6 at the tested concentrations did not differentiate between service-exposed and solution annealed specimens for their corrosion susceptibility. Slow strain rate testing of Type 347 SS in both the service-exposed and solution annealed conditions showed susceptibility to stress corrosion cracking in environment containing NaCl + H2S, while the alloy did not show susceptibility to SCC in H2SO4 and K2S4O6. The long-term service exposure did not noticeably influence the SCC susceptibility of Type 347 SS under the tested conditions.

Acoustic detection of stress-corrosion cracking of nitrogen austenitic steels

2014 ◽  
Vol 115 (6) ◽  
pp. 586-599 ◽  
Author(s):  
Yu. I. Filippov ◽  
V. V. Sagaradze ◽  
V. A. Zavalishin ◽  
N. L. Pecherkina ◽  
N. V. Kataeva ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Austenitic Steels ◽  
Acoustic Detection ◽  
Detection Of Stress

Benchmarking Study on Probabilistic Fracture Mechanics Analysis Codes xLPR and PASCAL-SP Considering Primary Water Stress Corrosion Cracking

2021 ◽  
Author(s):  
Akihiro Mano ◽  
Jinya Katsuyama ◽  
Yinsheng Li
Keyword(s):  
Water Stress ◽  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Structural Integrity ◽  
Corrosion Cracking ◽  
Pressurized Water ◽  
Probabilistic Fracture Mechanics ◽  
Primary Water ◽  
Failure Probabilities

Abstract Probabilistic fracture mechanics (PFM) is expected as a more rational methodology for the structural integrity assessments of nuclear power components because it can consider the inherent probabilistic distributions of various influencing factors and quantitatively evaluate the failure probabilities of the components. The Japan Atomic Energy Agency (JAEA) has developed a PFM analysis code, PASCAL-SP, to evaluate the failure probabilities of piping caused by aging degradation mechanisms, such as fatigue and stress corrosion cracking in the environments of both pressurized water and boiling water reactors. To improve confidence in the analysis results obtained from PASCAL-SP, a benchmarking study was conducted together with the PFM analysis code, xLPR, which was developed jointly by the U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute. The benchmarking study was composed of deterministic and probabilistic analyses related to primary water stress corrosion cracking in a dissimilar metal weld joint in a pressurized water reactor surge line. The analyses were conducted independently by NRC staff and JAEA using their own codes and under common analysis conditions. In the present paper, the analysis conditions for the deterministic and probabilistic analyses are described in detail, and the analysis results obtained from the xLPR and PASCAL-SP codes are presented. It was confirmed that the analysis results obtained from the two codes were in good agreement.

Mechanisms of stress corrosion cracking of irradiated austenitic chromium-nickel steels used for WWER and PWR vessel internals

2020 ◽  
pp. 174-199
Author(s):  
B. Z. Margolin ◽  
N. E. Pirogova ◽  
A. A. Sorokin ◽  
V. I. Kokhonov
Keyword(s):  
Energy Spectrum ◽  
Stress Corrosion ◽  
Neutron Energy ◽  
Stress Corrosion Cracking ◽  
Water Environment ◽  
Corrosion Cracking ◽  
Austenitic Steels ◽  
Neutron Energy Spectrum ◽  
Damage Dose ◽  
Loading Modes

This paper presents results of a corrosion cracking test of specimens of irradiated austenitic chromium- nickel steels of grades 321 (Kh18N10T), 316 (06Kh16N11M3) and 304 (02Kh18N9). Specimens were irradiated to different damage dose from 4.5 to 150 dpa. The tests were carried out in autoclaves in the water environment simulating a coolant of the first circuit of WWER reactors at temperatures of 290–315°С. The influence of the damage dose and the neutron energy spectrum on the tendency of steels to stress corrosion cracking (SCC) is analyzed. The dominant SCC mechanisms for various austenitic steels are determined. Loading modes effects on the SCC resistance of specimens irradiated to the same damage dose are compared.

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