Proposal of guidelines for structural integrity assessment on thermal aging embrittlement of cast austenitic stainless steel in BWR environment

2019 ◽  
Vol 2019 (0) ◽  
pp. OS1316
Author(s):  
Yasufumi MIURA ◽  
Taku ARAI
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Thermal Aging ◽  
Structural Integrity ◽  
Integrity Assessment

European Project ATLAS+: Status of the WP1 Relative to the Experimental Program on Pipes and Specimens

2020 ◽  
Author(s):  
Dominique Moinereau ◽  
Tomas Nicak ◽  
Anna Dahl
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Large Scale ◽  
Structural Integrity ◽  
Assessment Tools ◽  
Ductile Material ◽  
Experimental Program ◽  
Small Scale ◽  
Integrity Assessment ◽  
European Project

Abstract The 4-year European project ATLAS+ (Advanced Structural Integrity Assessment Tools for Safe long Term Operation) was launched in June 2017. One of its objectives is to study the transferability of ductile material properties from small scale specimens to large scale components and validate some advanced tools for structural integrity assessment. The study of properties transferability is based on a wide experimental program — within the framework of work-package 1 (WP 1) — which includes a full set of fracture experiments conducted on conventional fracture specimens and on large scale components (mainly pipes). Three materials are considered in the program: a low-alloy ferritic steel 15NiCuMoNb5 (WB36) typical from feedwater line in German PWR, an aged austenitic stainless steel weld typical (narrow gap) from EPR and a typical VVER austenitic stainless steel dissimilar weld (DMW). Several European organizations are involved in the experimental work: EDF, CEA, Framatome, ARMINES, KIWA, Framatome GmbH, VTT, BZN, MTA-EK, and CIEMAT.

Elastic-Plastic Fracture Mechanics Analysis of Cast Stainless Steel Pipes (Influence of Axial Load on Z-Factor of Pipes With Circumferential Crack Under Bending Load)

2013 ◽  
Author(s):  
Masayuki Kamaya ◽  
Kiminobu Hojo
Keyword(s):  
Stainless Steel ◽  
Axial Load ◽  
Power Plants ◽  
Structural Integrity ◽  
Term Operation ◽  
Steel Pipes ◽  
Integrity Assessment ◽  
Plastic Failure ◽  
Elastic Plastic ◽  
Bending Load

Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of cracked pipes. In the ASME Section XI, the load multiplier (Z-factor) is used to derive the elastic-plastic failure of the cracked components. The Z-factor of cracked pipes under bending load has been obtained without considering the axial load. In this study, the influence of the axial load on Z-factor was quantified through elastic-plastic failure analyses under various conditions. It was concluded that the axial load increased the Z-factor; however, the magnitude of the increase was not significant, particularly for the main coolant pipes of PWR nuclear power plants.

Hydro-Abrasive Wear Damage at Reactor Recirculation Pump Bearing Journals

2012 ◽  
Author(s):  
Robert Engel ◽  
André Fibier ◽  
Jens Heldt ◽  
Andreas Ronecker
Keyword(s):  
Stainless Steel ◽  
Heat Exchanger ◽  
Power Plant ◽  
Austenitic Stainless Steel ◽  
Regulatory Authority ◽  
Material Removal ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Erosion Mechanism ◽  
Wear Damage

During the refueling and maintenance outage in August 2011 at Leibstadt Nuclear Power Plant in Switzerland, the inspection of the hydrostatic bearings of the two identical recirculation pumps revealed a deep circumferential erosion groove on the inside surface of each of the bearing journals. The bearing journals are made of austenitic stainless steel. The cylindrical journal is welded to the back shroud of the impeller and surrounds the internal stationary heat exchanger of the pump by forming a narrow fluid filled annulus. The location of material removal was the same as in the year 2004 when similar wear damage was fixed by build-up welding. The plant decided to repair the damage during the subsequent outage in 2012. However, the Swiss Federal Nuclear Safety Inspectorate in return required the plant to identify the precise erosion mechanism, to ensure the structural integrity of the journals by taking into account the rate of material removal from 2004 up to the 2012 outage, and to include provisions for the early detection of a journal failure. This paper summarizes the previous as well as the latest results of different inspections, investigations, evaluations, and analyses done to meet the requirements of the Swiss regulatory authority. The results show that, from a safety-related and an operational availability perspective, it is acceptable not to repair the damaged bearing journals prior to the 2012 outage.

Spent Fuel Canister Probabilistic Confinement Integrity Assessment

2017 ◽  
Author(s):  
John E. Broussard ◽  
Shannon Chu ◽  
Kevin Fuhr
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Probabilistic Model ◽  
Population Based ◽  
Corrosion Cracking ◽  
Spent Fuel ◽  
Integrity Assessment ◽  
Induced Stress

A probabilistic model was developed that considers the likelihood of through-wall penetration of chloride-induced stress corrosion cracking (CISCC) in austenitic stainless steel canisters and compares different population-based sample inspection regimes. This paper describes the inputs and methods used to simulate multiple canisters with a range of susceptibilities. This paper also summarizes results of key illustrative cases.

Environmental Crack Growth Predictions for Piping Components

2007 ◽  
Author(s):  
Sam Ranganath ◽  
Guy DeBoo
Keyword(s):  
Stainless Steel ◽  
Crack Growth ◽  
Test Data ◽  
Structural Integrity ◽  
Reference Curve ◽  
Pressurized Water ◽  
Water Reactor ◽  
Integrity Assessment ◽  
Asme Code ◽  
Reference Curves

Structural integrity assessment of reactor components requires consideration of crack growth. A key input to this is the development of reference stress corrosion crack (SCC) growth rate curves for use in the structural evaluation. The ASME Section XI Task Group on SCC Reference Curve is looking into available SCC data for stainless steel and nickel based alloys and associated weldment in both pressurized water reactor (PWR) and boiling water reactor (BWR) environments. The test data show significant data scatter in crack growth rates (CGR). The conservative approach is to develop reference curves that bound all available data so that upper bound crack growth predictions. While this approach may be conservative, it may lead to excessive estimates of crack growth and result in unrealistic (and often meaningless) structural margin predictions. Selection of the appropriate SCC reference curves requires realistic interpretation of test data so that the predictions are consistent with field behavior and provide reasonable, but conservative assessment. This paper describes crack growth assessment for stainless steel piping and Alloy 600 safe end components with Alloy 182/82 welds in BWR environment. The results from the crack growth analysis for piping can be used to determine whether a proposed reference curve provides reasonable results. The objective is to use the piping and safe end crack growth predictions to develop optimal SCC Reference Curves for use in ASME Code evaluations.

Risk-Informed Structural Integrity Management: Development of SMR-Centric Piping Reliability Models

2014 ◽  
Author(s):  
Bengt Lydell
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Structural Integrity ◽  
Degradation Mechanism ◽  
Management Strategies ◽  
Mitigation Strategies ◽  
Parameter Estimates ◽  
Piping System ◽  
Reliability Models ◽  
Integrity Management

In the context of risk-informed applications, this paper addresses the progress with piping reliability analysis methods and techniques and their role in supporting development of risk-informed structural integrity programs for small modular reactors (SMRs). The structural integrity of a pressure boundary is determined by multiple and interrelated reliability attributes and influence factors. Depending on the conjoint requirements for damage and degradation, certain combinations of material, operating environment, loading conditions together with applicable design codes and standards, certain passive components are substantially more resistant to damage and degradation than others. As an example, for stabilized austenitic stainless steel pressure boundary components, there are no recorded events involving active, through-wall leakage. By contrast, for unstabilized austenitic stainless steel, multiple events involving through-wall leakage have been recorded, albeit with relative minor leak rates. The field experience with safety- and non-safety related piping in commercial GenI through GenIII nuclear power reactors is quite extensive. Equally extensive is the experience gained from the implementation of different degradation mechanism mitigation strategies. By applying advanced piping reliability models, this body engineering data and integrity management insights can be used to assess the projected structural integrity of new piping system designs, including those of SMRs. The paper presents an overview of recent methodological advances and insights from the application of statistical piping reliability models to advanced reactor designs. Examples are provided on how piping reliability parameter estimates are affected by different integrity management strategies as well as by advanced, degradation mechanism (DM) resistant materials. The technical basis for the work that is presented in this paper has evolved over a period of 20+ years of focused and sustained R&D in the area of statistical models of piping reliability.

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