Toward a Mechanistic Model of Stress Corrosion Cracking in PHWR Fuel Sheaths

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Andrew Oussoren ◽  
Paul Chan ◽  
Diane Wowk ◽  
Andrew Prudil
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Failure Time ◽  
Mechanistic Model ◽  
Corrosion Cracking ◽  
Performance Model ◽  
Operating Conditions ◽  
Mechanistic Modeling ◽  
Release Rates ◽  
Hoop Strain

Abstract This work builds on the iodine-induced stress corrosion cracking (ISCC) model of Lewis and Kleczek by integrating the fuel performance model fuel and sheath modeling tool (FAST) to provide thermal and mechanical analysis of the fuel sheath, which was previously required as input parameters. The iodine transport methodology of the Lewis–Kleczek model has been modified to utilize the more mechanistic diffusion model in FAST, and an empirical surface multiplier term has been derived to predict iodine release rates under normal operating conditions based on measured release rates from in-reactor sweep gas tests. A fracture mechanics analysis is implemented using threshold stress intensity values and crack growth rates reported in literature. A correlation to predict crack initiation has been derived by analysis of a database of power histories with known ISCC defects. This correlation is based on the change in sheath hoop strain during a power ramp and is shown to be more accurate at discerning failure versus nonfailure than the correlations used in the previous Lewis–Kleczek model and FUELOGRAMS. Failure time prediction of the model is compared against power ramp test FFO-104 performed at the National Research Experimental (NRX) reactor. Fuel failure is predicted to occur 27% faster than experimentally measured; failure time is explored in a series of sensitivity studies to suggest areas for further development. The model improvements represent a step forward in the mechanistic modeling of stress corrosion cracking (SCC) in pressurized heavy water reactor (PHWR) nuclear fuel.

Effects of Weld Overlays on Leak-Before-Break Margins

2011 ◽  
Author(s):  
G. Angah Miessi ◽  
Peter C. Riccardella ◽  
Peihua Jing
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Intergranular Stress Corrosion ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Water Reactors ◽  
Weld Overlays ◽  
Leak Before Break

Weld overlays have been used to remedy intergranular stress corrosion cracking (IGSCC) in boiling water reactors (BWRs) since the 1980s. Overlays have also been applied in the last few years in pressurized water reactors (PWRs) where primary water stress corrosion cracking (PWSCC) has developed. The weld overlay provides a structural reinforcement with SCC resistant material and favorable residual stresses at the ID of the overlaid component. Leak-before-break (LBB) had been applied to several piping systems in PWRs prior to recognizing the PWSCC susceptibility of Alloy 82/182 welds. The application of the weld overlay changes the geometric configuration of the component and as such, the original LBB evaluation is updated to reflect the new configuration at the susceptible weld. This paper describes a generic leak-before-break (LBB) analysis program which demonstrates that the application of weld overlays always improves LBB margins, relative to un-overlaid, PWSCC susceptible welds when all the other parameters or variables of the analyses (loads, geometry, operating conditions, analysis method, etc…) are kept equal. Analyses are performed using LBB methodology previously approved by the US NRC for weld overlaid components. The analyses are performed for a range of nozzle sizes (from 6″ to 34″) spanning the nominal pipe sizes to which LBB has been commonly applied, using associated representative loads and operating conditions. The analyses are performed for both overlaid and un-overlaid configurations of the same nozzles, and using both fatigue and PWSCC crack morphologies in the leakage rate calculations and the LBB margins are compared to show the benefit of the weld overlays.

Applicability of Formula of the Irradiation Assisted Stress Corrosion Cracking Rates for Neutron-Irradiated Type 316L Stainless Steels to Various Types of Stainless Steels Under Boiling Water Reactor Condition

2020 ◽  
Author(s):  
Masato Koshiishi ◽  
Hitoshi Seto ◽  
Shigeaki Tanaka ◽  
Ryoji Obata
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Mechanistic Model ◽  
Corrosion Cracking ◽  
The Other ◽  
Type 316L ◽  
Type 304 ◽  
Crack Growth Rates ◽  
Simplified Formula

Abstract The Hashimoto-Koshiishi model is the predictive mechanistic model for crack growth rates (CGRs) of stress corrosion cracking (SCC). The simplified formula of the Hashimoto-Koshiishi model was developed for the calculation of CGRs of irradiated Type 316L stainless steels (SSs). This study evaluated the applicability of the developed formula to various types of stainless steels by analyzing experimental data of CGRs. The developed formula was determined to be applicable for Type 304L SSs and 316NG SSs as well as Type 316L SSs. On the other hand, the formula was unsuitable for irradiated Type 304 SSs because the mechanical properties and the Cr concentrations at the grain boundaries of Type 304 SSs were different from these quantities for Type 316L SSs.

scholarly journals ЗАКОНОМІРНОСТІ КОРОЗІЙНОГО РОЗТРІСКУВАННЯ ТРУБНОЇ СТАЛІ 10Г2ФБ У МОДЕЛЬНОМУ ГРУНТОВОМУ СЕРЕДОВИЩІ ЗА КАТОДНОЇ ПОЛЯРИЗАЦІЇ

2021 ◽  
pp. 29-39
Author(s):  
LYUDMILA NYRKOVA ◽  
PAVLO LISOVYI ◽  
LARYSA GONCHARENKO ◽  
SVETLANA OSADCHUK ◽  
ANATOLIY KLYMENKO ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Cathodic Polarization ◽  
Corrosion Potential ◽  
Relative Elongation ◽  
Corrosion Cracking ◽  
Polarization Potential ◽  
Operating Conditions ◽  
Soil Environment ◽  
Model Soil

Purpose. Investigate the regularities of corrosion cracking of 10G2FB steel under cathodic protection.Methodology. The following methods were used: slow strain rate, scanning electron microscopy, electrolytic hydrogenation, mass measurement.Results. The regularities of corrosion cracking of pipe steel 10G2FB in near neutral soil environment NS4 in the range of potentials from the corrosion potential to -1.2 V were investigated. According to the results of a complex of corrosion-mechanical, electrochemical and physical studies, it was found that with a shift in the cathodic polarization potential in the range of -0,75 V ® -0,95 V ® -1,05 V ® -1,2 V ® -0.95 V the coefficient of susceptibility of this steel to stress corrosion cracking KS increases correspondingly, 1,09 ® 1,11 ® 1,13 ® 1,26. The concentration of hydrogen which penetrating into steel at these potentials changes nonmonotonically: 0 ® 0 ® 0,057 ® 0,018 mol/dm3. The rate of residual corrosion with a potential shift in the series Еcor ® -0,75 V ® -0,95 V ® -1,05 V decreases first sharply, then slowly: 0.035 mm/year ® 0.005 mm/year ® 0.0009 mm/year ® 0.0004 mm/year, i.e. at high cathodic potentials, the applied polarization is spent on the decomposition of the aqueous electrolyte with the release of hydrogen, which penetrates into the steel and causes brittle cracking, which is confirmed by an increasing in the part of brittle fracture in the surface morphology of the specimens.Scientific originality. New results of fundamental research concerning the regularities of stress-corrosion cracking of ferrite-pearlite class steel of pipe assortment 10G2FB under conditions of cathodic protection in the range of potentials from the corrosion potential to -1.2 V have been obtained. It was revealed that a feature of the effect of cathodic polarization in the indicated range of potentials when assessing the tendency to stress corrosion cracking by the KS coefficient is an increasing in the relative narrowing and a decrease in the relative elongation, which generally indicates the embrittlement of the metal under the contact with corrosive medium and potential. Strength characteristics remain almost the same. The greatest tendency to stress-corrosion cracking is observed at a polarization potential of -1.0 V or more negative.Practical value. The developed methodology for a complex study of the regularities of stress- corrosion cracking was used for study of 10G2FB steel of the pipe assortment in a model soil environment NS4 under conditions simulating operating conditions. The new data obtained on the regularities of stress-corrosion cracking of steel will be useful for preventing the stress-corrosion cracking of main gas pipelines during operation.

scholarly journals Stress Corrosion Cracking of Steel and Aluminum in Sodium Hydroxide: Field Failure and Laboratory Test

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Y. Prawoto ◽  
K. Sumeru ◽  
W. B. Wan Nik
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Laboratory Test ◽  
Stress Corrosion ◽  
Sodium Hydroxide ◽  
Stress Corrosion Cracking ◽  
Crack Depth ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Field Failure

Through an investigation of the field failure analysis and laboratory experiment, a study on (stress corrosion cracking) SCC behavior of steel and aluminum was performed. All samples were extracted from known operating conditions from the field failures. Similar but accelerated laboratory test was subsequently conducted in such a way as to mimic the field failures. The crack depth and behavior of the SCC were then analyzed after the laboratory test and the mechanism of stress corrosion cracking was studied. The results show that for the same given stress relative to ultimate tensile strength, the susceptibility to SCC is greatly influenced by heat treatment. Furthermore, it was also concluded that when expressed relative to the (ultimate tensile strength) UTS, aluminum has similar level of SCC susceptibility to that of steel, although with respect to the same absolute value of applied stress, aluminum is more susceptible to SCC in sodium hydroxide environment than steel.

Application of Failure Event Data to Benchmark Probabilistic Fracture Mechanics Computer Codes

2007 ◽  
Author(s):  
F. A. Simonen ◽  
S. R. Gosselin ◽  
B. O. Y. Lydell ◽  
D. L. Rudland ◽  
G. M. Wilkowski
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Operating Experience ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Intergranular Stress Corrosion ◽  
Probabilistic Fracture Mechanics ◽  
Computer Codes

This paper describes an application of data on cracking, leak and rupture events from nuclear power plant operating experience to estimate failure frequencies for piping components that had been previously evaluated using the PROLOCA and PRAISE probabilistic fracture mechanics (PFM) computer codes. The calculations had addressed the failure mechanisms of stress corrosion cracking, intergranular stress corrosion cracking and fatigue for materials and operating conditions that were known to have failed components. The first objective was to benchmark the calculations against field experience. A second objective was a review of uncertainties in the treatments of the data from observed failures and in the structural mechanics models. The database PIPExp-2006 was applied to estimate failure frequencies. Because the number of reported failure events was small, there were also statistical uncertainties in the estimates of frequencies. Comparisons of predicted and observed failure frequencies showed that PFM codes correctly predicted relatively high failure probabilities for components that had experienced field failures. However, the predicted frequencies tended to be significantly greater than those estimated from plant operating experience. A review of the PFM models and inputs to the models showed that uncertainties in the calculations were sufficiently large to explain the differences between the predicted and observed failure frequencies.

Validation of Constant Load C-Ring Apex Stresses for Stress Corrosion Cracking Testing in Supercritical Water

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
R. Swift ◽  
W. Cook ◽  
C. Bradley ◽  
R.C. Newman
Keyword(s):  
Thermal Expansion ◽  
Stress Corrosion ◽  
Supercritical Water ◽  
Stress Corrosion Cracking ◽  
Mechanistic Model ◽  
Constant Load ◽  
Corrosion Cracking ◽  
Ambient Conditions ◽  
Operational Conditions ◽  
Ring Assembly

In selecting the materials for the Canadian supercritical water-cooled reactor (SCWR), the effects and extent of stress corrosion cracking (SCC) on candidate alloys of construction, under various operational conditions, must be considered. Several methods of applying stress to a corroding material are available for investigating SCC and each have their benefits and drawbacks; for simplicity of the experimental setup at University of New Brunswick (UNB), a constant load C-ring assembly has been used with Inconel 718 Belleville washers acting as a spring to deliver a near-constant load to the sample. To predict the stress at the apex of the C-ring, a mechanistic model has been developed to determine the force applied by the spring due to the thermal expansion of each component constrained within a fixed length when the temperature of the assembly is increased from ambient conditions to SCWR operational temperatures. In an attempt to validate the mechanistic model, trials to measure the force applied by the washers as the assembly thermally expanded were performed using an Instron machine and an environmental chamber. Accounting for the thermal expansion of the pull rods, the force was measured as temperature was increased while maintaining a constant displacement between the platens holding the C-ring. Results showed the initial model to be insufficient as it could not predict the force measured through this simple experiment. The revised model presented here considers the thermal expansion of the C-ring and all the components of the testing apparatus including the tree, backing washers, and Belleville washers. Further validation using the commercial finite element (FE) package abaqus is presented, as are preliminary results from the use of the apparatus to study the SCC of a zirconium-modified 310 s SS exposed to supercritical water.

scholarly journals Environmental effect on corrosion behavior of 9MnSi5 steel pipelines

2020 ◽  
Vol 221 ◽  
pp. 02001
Author(s):  
Aleksey Alkhimenko ◽  
Boris Ermakov ◽  
Ekaterina Alekseeva ◽  
Artem Davidov ◽  
Mark Kovalev ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Environmental Effect ◽  
Residual Life ◽  
Corrosion Damage ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Resistance Testing ◽  
Fluid Forces ◽  
Safe Operating

The increase in the corrosiveness of the produced fluid forces to reconsider the attitude towards the assessment of the serviceability and reliability of oil pipes, paying attention to the problems of increasing their corrosion resistance. The paper analyses environmental impact on pipeline made of 9MnSi5 steel after 12 months of operation in the oilfield to assess the residual life of pipeline and determine safe operating conditions. It was found that corrosion damage developed according to the mechanisms of general, pitting corrosion and stress corrosion cracking. Metallographic study has shown cracks of stress corrosion cracking that developed in environments containing carbon dioxide and hydrogen sulfide. Accelerated method of stress corrosion cracking resistance testing was implemented that allows to understand the tendency of steel to this type of cracking and gives a conclusion about the danger of brittle fracture of the pipeline.

Fitness for Service Assessments on Cracked Heavy Wall Reactors

2018 ◽  
Author(s):  
Jan Keltjens ◽  
Gys Van Zyl ◽  
Fahad Mudhayeq
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Water Environment ◽  
High Hardness ◽  
High Strength ◽  
Crack Size ◽  
Economic Benefits ◽  
Corrosion Cracking ◽  
Operating Conditions ◽  
Feed Water

A number of large heavy wall reactors showed severe stress corrosion cracking in the high strength low alloy steel shells. The stress corrosion was mainly caused by the fact that no PWHT was performed which resulted in very high hardness of the Heat Affected Zone; this made the HAZ extremely sensitive for stress corrosion cracking in the feed water environment. The extent of the cracking was such that replacement of all reactors was unavoidable. The redesign and fabrication of the new reactors would take over a year. Fitness for Service methodologies were used keep the reactors running safely until the replacements were installed with minimized down time. This resulted in large economic benefits over several years. The paper covers the FFS assessments performed, the special NDT methods required to get the necessary crack size information at operating conditions as well as failure mode and repair options. It demonstrates an application and the benefits of Fitness for Service assessments on key equipment.

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