Jürgen Rudolph

• Senior Expert at Framatome

The fatigue assessment of safety relevant components is of importance with regard to safety and reliability of nuclear power plants. Due to their excellent mechanical and technological properties as well as their corrosion resistance austenitic stainless steels are often used for reactor internals. Internals are subject to mechanical and thermo-mec...

Welded joints are critical areas of components exposed to cooling water in NPP. For the improvement of the safety-critical fatigue design, an accurate analysis of the fatigue behavior in corrosive medium is essential. For this purpose, ER 347 weld material with its increased ferrite content and AISI 304 were investigated in medium conditions. Fatig...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. Austenitic stainless steels are often used for reactor internals due to their excellent mechanical and technological properties as well as their corrosion resistance. During operation reactor i...

The fatigue analyses included in nuclear rules of KTA [1]–[2] and ASME [3] are based on defined loads (specified or measured loads and frequencies). It is assumed that highly cyclic loadings or resonance vibrations are avoided by appropriate design. Often these loads are recorded by measurements during commissioning or during operation. In particul...

The Fatigue lifetime assessment of pressurized components e.g. in nuclear power plants (NPPs) is an essential part of the aging management (AM) ensuring safe and reliable long term operation (LTO). The practically applied calculation procedures of different international codes and standards are widely affected by the basic principles formulated in...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. Austenitic stainless steels are often used for reactor internals due to their excellent mechanical and technological properties as well as their corrosion resistance. During operation reactor int...

Thermal-hydraulic phenomena with relevance to thermal fatigue are thermal shock, thermal stratification, mixing zones and vortex penetration. The last mentioned is also known as the "Farley-Tihange" phenomenon. Damage caused by this particular kind of high-cycle thermal fatigue (HCF) can occur in piping systems at locations where part of the liquid...

In the framework of fatigue assessment of Nuclear Power Plant (NPP) components, Environmentally Assisted Fatigue (EAF) is nowadays receiving an increased level of attention by regulatory bodies, code committees and utilities worldwide. This concerns particularly the Long Term Operation (LTO) of NPPs, where EAF may impact significantly the stress re...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability. Those components are subjected to low cycle (LCF), high cycle (HCF), very high cycle fatigue (VHCF) and their combination in terms of complex loading collectives and nonlinear fatigue damage accumulation. Reactor intern...

In the past, lifetime consideration of conventional power plant components focused on the creep behavior under internal pressure loading. Changing operating conditions towards flexible loads and load cycles as well as occurring damages underline the necessity to consider the fatigue and creep-fatigue behavior of the components. It is recommendable...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. For reactor internals, austenitic stainless steels are often used due to their excellent mechanical and technological properties as well as their corrosion resistance. During operation the materi...

The European Pressure Vessel Standard EN 13445 (harmonized Standard acc. to PED 2014/68/EU) provides in its Part 3 (Design) a simplified method for fatigue assessment (Clause 17) and a detailed method of fatigue assessment (Clause 18). While the new revision of Clause 17 has already been adopted, Clause 18 “Detailed Assessment of Fatigue Life” is n...

The fatigue assessment of pressure boundary components is of importance for the aging management regarding safety and reliability in nuclear power plants with light water reactors. For the evaluation of cyclic loading conditions, different country specific design codes and standards are applied to consider various mechanical and thermal loadings as...

Power plant component condition monitoring with respect of fatigue and creep-fatigue requires information about the real operational loading of the component. Load monitoring systems are available on the market for that purpose. The retrieved load information can be further processed in terms of fatigue assessment based on realistic loading. Moreov...

The European Pressure Vessel Standard EN 13445 (harmonized Standard acc. to PED 2014/68/EU) provides in its Part 3 (Design) a simplified method for fatigue assessment (Clause 17) and a detailed method of fatigue assessment (Clause 18). While the new revision of Clause 17 has already been adopted, Clause 18 “Detailed Assessment of Fatigue Life” is n...

This paper summarizes the results of a research project on environmental effects on the fatigue lifetime of selected low-alloy steels and austenitic stainless steels. Results from investigations on the effect of hold times during fatigue in air, as well as under simulated PWR primary water conditions are presented. Strain controlled fatigue tests w...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. Reactor internals are subjected to thermo-mechanical fatigue induced by operational temperature transients and to flow induced vibrations. The resulting complex loading collectives induce low cyc...

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18) of unwelded and welded components. Clause 18 “Detailed Assessment of Fatigue Life” is under principal revision within the framework of the European working group “CEN/TC 54/WG 53 – D...

Components of power plants are often subjected to thermo-mechanical loading conditions. Thermal loadings alone are strain-controlled loadings, inducing locally high mechanical strains and stresses, which may result in low cycle fatigue issues. Furthermore, these cycles are mixed with numerous cycles of lower stress and strain ranges. Regarding appl...

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 – Design methods with the aim of reaching a sign...

The fatigue assessment of welded joints in different engineering disciplines is usually based on nominal, structural or notch stresses on one hand (elastic concept using component fatigue curves of load controlled test data) and local strains on the other hand (elasto-plastic concept using material fatigue curves of strain-controlled push-pull test...

This paper presents a structural integrity evaluation of a duplex stainless steel pressure vessel containing several flaws detected in a longitudinal weld. The evaluation had the objective of determining whether the pressure vessel was suitable to continue in operation or whether it should be immediately repaired or even replaced. Due to timely iss...

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first des...

The load follow operation of thermal power plants in the context of the German “Energiewende” is a big challenge for those power plants. In this context TMF/SHM methods gain increasingly in importance. Most existing power plants do not actually work any more according to the load profile which was originally specified. Load monitoring with the pote...

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 - Design methods to reach a significant increase...

Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strai...

Applicable design codes for power plant components and pressure vessels demand for a design check against progressive plastic deformation. In the simplest case, this demand is satisfied by compliance with shakedown rules in connection with elastic analyses. The possible noncompliance implicates the requirement of ratcheting analyses on elastic-plas...

en Strukturmechanische Belastungen unterscheiden sich maßgeblich von thermischen und somit verformungskontrollierten Belastungen, was sich insbesondere bei der Anwendung von herkömmlichen Kerbnäherungsverfahren zeigt. Im Rahmen dieser Ausarbeitung wird eine Methodik präsentiert, die es erlaubt, elastisch‐plastische Kerbbeanspruchungen infolge therm...

Fatigue life assessment for pressurized components in nuclear power plants (NPPs) is an essential part of the aging management (AM) ensuring safe and long term operation (LTO). For fatigue life assessment different codes and standards provide a variety of methodologies with variable complexity. Major fatigue life influencing factors such as tempera...

This paper points out some relevant aspects of the simplified elasto-plastic fatigue analysis as addressed in the ASME Code Section III Subsection NB and its application to two structural components that are subjected to a slow or to a fast thermal transient. The structural components considered are a thick-walled pipe and a nozzle-to-vessel juncti...

Modern state-of-the-art fatigue monitoring approaches gain in importance in the context of renewables such as wind power plants. Fatigue is of utmost importance in terms of potential damage mechanisms and in the perspective of scheduled plant lifetime periods of 20 years. A qualified fatigue monitoring approach considering the real loads provides-t...

A statistical model for austenitic stainless steels for predicting the effect of pressurized water reactor (PWR) environments on fatigue life for a range of temperatures and strain rates is developed based on analysis of available material data from USA, Europe, and Japan. Only fatigue data from polished specimens of wrought material tested under s...

A statistical model for austenitic stainless steels for predicting the effect of pressurized water reactor environments on fatigue life for a range of temperatures and strain rates is developed based on analysis of available material data. The compiled fatigue curve data include not only results from America (Keller (1971), Conway (1975), Hale (197...

Seam welds in technical plants are often subjected to thermal loading conditions, e.g. thermal transients in the low cycle fatigue range. Corresponding to this fact, the failure of seam welds under Low Cycle Fatigue (LCF) must be predictable, to avoid cases of damage. A commonly used material for pipelines of power plants is the austenitic stainles...

Qualified fatigue assessment based on realistic input data constitutes an essential part of an ageing management strategy for Nuclear Power Plants. In this context and as a continuation of a previous paper PVP2014-28716 the requirements of load data evaluation, stress analysis and cycle counting are detailed based on a real world example from a Bra...

Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strai...

Consideration of Environmentally Assisted Fatigue (EAF) has been introduced to the German Regulatory Framework with the November 2013 revision of the German Safety Standard KTA 3201.2. Therefore, so called threshold of attention values by means of the cumulative usage factor have been included in the German KTA Program of Standards for the design o...

For plant lifetime extension programs, several products provide a customized solution for thermal load monitoring and fatigue calculation. Requirements like the consideration of Environmentally Assisted Fatigue (EAF) effects or flexible plant (e.g. load follow) operation have a crucial impact on the engineering practice of a detailed fatigue assess...

The ageing management of power plants is nowadays a main issue for all nuclear industry actors: states, regulatory agencies, operators, designers or suppliers. Consequently, lots of operators have to deal with demanding safety requirements to ensure the operation of power plants particularly in the context of lifetime extension. With regard of the...

The fatigue behavior of the austenitic stainless steel X6CrNiNb18‐10 (1.4550, AISI 347) is investigated. Experimental data are generated at room temperature, at elevated temperatures and further under thermo‐mechanical conditions. Research is focused on generating data for parameter identification, especially for the improvement of material models....

The strip-yield model is a common tool to calculate the cyclic crack tip opening displacement and the fatigue crack growth life of structures in case of isothermal fatigue loading. The incorporation of a temperature-dependent yield stress already enables its application in thermal fatigue analyses. A further extension of the strip-yield model is pr...

Nowadays, the abbreviation LTO (Long Term Operation) is well known in the NPP's world. No other kind of projects can ensure the actual economic and environmental questions of the world of energy production with this high efficiency. Two-thirds of the actual international NPP fleet in operation has reached an age of more than 25 years. The former NP...

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability. For cyclic stress evaluation, different country specific design codes and standards provide fatigue analysis procedures to be performed considering the various mechanical and thermal loading histories and geometric comp...

Austenitic stainless steel of type X6CrNiNb18-10 (1.4550) is a widely used material in piping and components of nuclear power plants. The fatigue behavior of these components is often operationally determined by thermomechanical strains and corresponding stresses. Welded structures lead to complex stresses in the component and potential fatigue lif...

Modern state-of-the-art fatigue monitoring approaches gain in importance as part of the ageing management of conventional and nuclear power plant components (NPP) and particularly in the context of lifetime extension projects and new plants. A key feature of qualified fatigue monitoring is the measurement of realistic loads based on plant instrumen...

Components of conventional power plants are subject to three potential damage mechanisms and their combination (accumulation) with impact on lifetime considerations: creep, fatigue and ratcheting. Currently, there is a growing need for advanced material models which are able to simulate these damage phenomena and can be implemented effectively with...

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method for fatigue assessment (Clause 17) and a detailed method of fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 - Design methods. The late...

The first results of a detailed fatigue model for austenitic stainless steels in general and for the grades 1.4541 and 1.4550 are presented to describe the effect of the light water reactor (LWR) coolant environments on the fatigue life. The statistical evaluations are based on strain (and load) controlled test series from different institutions. T...

Modern state-of-the-art fatigue monitoring approaches gain in importance not only as part of the ageing management of nuclear power plant components but also in the context of conventional power plants and renewables such as wind power plants. Consequently, lots of operators have to deal with demanding security requirements to ensure the safe opera...

As elastic-plastic fatigue analyses are still time consuming the simplified elastic-plastic analysis (e.g. ASME Section III, NB 3228.5, the French RCC-M code, paragraphs B 3234.3, B 3234.5 and B3234.6 and the German KTA rule 3201.2, paragraph 7.8.4) is often applied. Besides linearly elastic analyses and factorial plasticity correction (Ke-factors)...

This contribution deals with the low cycle fatigue behaviour of butt-welded joints of austenitic stainless steel (Type 347). The influence of the geometrical notch of a butt weld on the fatigue life in LCF regime is of particular interest in this context. For the purpose of comparison different weld geometries – as-welded and machined – are investi...

The fatigue assessment of power plant components based on local fatigue monitoring approaches is an essential part of the integrity concept and modern lifetime management. An integral approach like the AREVA Fatigue Concept (AFC) basically consists of two essential modules: realistic determination of occurring operational thermal loads by means of...

Titanium and niobium stabilized austenitic stainless steels X6CrNiTi18-10S (material number 1.4541, correspondent to Alloy 321) respectively X6CrNiNb18-10S (material number 1.4550, correspondent to Alloy 347) are widely applied materials in German nuclear power plant components. Related requirements are defined in Nuclear Safety Standard KTA 3201.1...

This contribution deals with the low cycle fatigue behavior of butt-welded joints of austenitic stainless steel (1.4550, type 347). The focus is on the problem how to model these welded joints adequately with the objective of its assessment. Thereby, the differences between as-welded and machined weld are considered, in addition. The considerations...

The ageing management of power plants is nowadays a main issue for all nuclear industry actors: states, regulatory agencies, operators, designers or suppliers. Consequently, lots of operators have to deal with demanding security requirements to ensure the operation of power plants. Regarding with fatigue assessment of nuclear components, stringent...

Two calibration processes are selected for determining the parameters of the Chaboche nonlinear kinematic hardening (NLK) material model for stainless steel. One process is manual that requires no outside software and the other follows a finite element software. The basis of the calibration is the monotonic stress-strain curve obtained from a tensi...

As elastic-plastic fatigue analyses are still time consuming the simplified elastic-plastic analysis (e.g. ASME Section III, NB 3228.5, the French RCC-M code, paragraphs B 3234.3, B 3234.5 and B3234.6 and the German KTA rule 3201.2, paragraph 7.8.4) is often applied. Besides linearly elastic analyses and factorial plasticity correction (Ke-factors)...

The ageing management of nuclear power plants (NPP) has gained an increasing importance in the last years. The reasons are mainly due to the international context of extending period of plants operation. The fatigue damage process takes a central position in ageing mechanisms of components. In the design phase of NPP, fatigue analyses are still bas...

An extension of the strip yield model towards the calculation of crack opening and closure under non-isothermal loading conditions is the main prerequisite for its applicability in thermal fatigue analyses. The aim of this contribution is to implement a new proposal to this feature. Here, the yield stress is allowed to be location and time dependen...

The Detailed Fatigue Calculation (DFC) of nuclear power plant components is part of the three staged approach to lifetime assessment and lifetime management of the AREVA Fatigue Concept (AFC). It is applied for fatigue relevant components showing high usage factors by application of the Simplified Fatigue Evaluation (SFE) and/or the Fast Fatigue Ev...

Nuclear power plant components are often subjected to local plastic deformations due to low cycle operational thermal loading conditions. The fatigue behavior of weld seams is of particular interest in this context. Applicable design codes for fatigue life assessment use factors (e.g. Fatigue strength reduction factors – FSRF) within the simplified...

The procedures of fatigue analyses of several relevant nuclear and conventional design codes (ASME, KTA, EN, AD) for power plant components differentiate between an elastic, simplified elastic-plastic and elastic-plastic fatigue check. As a rule, operational load levels will exclude the purely elastic fatigue check. The application of the code proc...

Cycle based counting is an internationally established procedure for the determination of fatigue usage factors in nuclear power plants. The AREVA fatigue concept (AFC) includes a three-stage approach to calculate the usage factors, utilising not only cycle based counting but additionally stress based fatigue analysis. This paper describes the deve...

The fatigue check of components has to be considered as an essential module of the safety concept as well as the ageing and lifetime management of nuclear power plants. It is based on special safety requirements in the design phase as well as in the framework of the ageing and lifetime management. Considerable efforts of load identification (fatigu...

As code-based fully elastic plastic code conforming fatigue analyses are still time consuming, simplified elastic plastic analysis is often applied. This procedure is known to be overly conservative for some conditions due to the applied plastification (penalty) factor Ke. As a consequence, less conservative fully elastic plastic fatigue analyses b...

Kurzfassung Der Nachweis der Betriebsfestigkeit ist wesentlicher Baustein des Sicherheitskonzeptes sowie des Alterungs- und Langzeitbetriebsmanagements kerntechnischer Anlagen. Hoher Aufwand zur Lastidentifikation (Fatigue Monitoring) und starke Regelwerksbindung sind kennzeichnend. Besonderheiten gegenüber anderen Technikbereichen stellen die Domi...

A framework of global ratcheting is developed for which the ratcheting measure is incremental permanent change of shape of a vessel or component. The changes of shape are such that they reduce the resistance to collapse, and, upon extended cycling, can lead to eventual failure by collapse. A ratcheting check is designed to prevent this failure. Thi...

Emanating from a discussion of local ratcheting effects and appropriate limiting criteria this paper examines existing ratcheting rules based on local (or material) response that are currently in Section III of the ASME B&PV Code, German KTA rules, and other design codes. The objective is to offer clarification of the rules that may be useful to th...

The fatigue assessment of components has to be considered as an essential module of the safety concept as well as the ageing and lifetime management of nuclear power plants. It is based on special safety requirements in the design phase as well as in the framework of the ageing and lifetime management. Considerable efforts of load identification (f...

Within the discussions on the long term operation (LTO) of nuclear power plants the ageing management is on the focus of that analysis. The knowledge of the operational thermal cyclic load data on components of the power plants and their evaluation in the fatigue analysis is a central concern. The changes in fatigue requirements (e.g. the considera...

Analysis of welded structures still remains a challenge for the analyst and in fact cannot be considered as fully solved for practical applications. For many years, a large international aggregation of researchers has developed methods to assess fatigue behaviour of welded structures. Nowadays many suggestions and methods exist to estimate fatigue...

Thermal loading conditions of nuclear power plant components cause local stress-strain hystereses. For the fatigue life prediction of nuclear power plant components under thermal cyclic and structural loading a new method based on the local strain approach is to be presented. This method involves finite-element simulations as well as the experience...

Thermal cyclic loading conditions of nuclear power plant components cause local stress-strain hystereses which are considered to be fatigue relevant events. The contributions of the hysteresis-loops to the fatigue process are evaluated using a damage parameter based on the effective cyclic J-integral which also includes the effects of crack closure...

Thermal loading conditions of nuclear power plant components cause local stress-strain hystereses. For the fatigue life prediction of nuclear power plant components under thermal cyclic and structural loading a new method based on the local strain approach is to be presented. This method involves finite-element simulations as well as the experience...

Avoiding fatigue-induced damage to components of nuclear power plant technology is an important prerequisite for maintaining plant safety and increasing availability. Fatigue monitoring is an integral part of plant aging and lifetime management. Against this background and changing framework conditions, such as design and construction of new nuclea...

Classical linearly elastic stress analysis can still be considered a principal practical application of the finite element (FE) method. It is in close relation-ship to problems of stress categorisation and evaluation according to the considered load case. The aim of the paper is to provide practical guidelines using concrete examples of power plant...

The service durability of weld seams is one of the most challenging problems of component fatigue. Hereby, the complexity is due to several peculiarities of welded structures: the detailed weld seam geometry with macroscopic and microscopic notch effects and/or defects, the properties of the welded material, residual stresses and multiaxial proport...

The service durability of weld seams is one of the most challenging problems of component fatigue. Hereby, the complexity is due to several peculiarities of welded structures: the detailed weld seam geometry with macroscopic and microscopic notch effects and/or defects, the properties of the welded material, residual stresses and multiaxial proport...

The sizing of dished ends in torispherical or semielliptical shape with or without nozzles based on pressure equipment codes and on design by rule (DbR) is a standard task. Although the design formulae are easy to handle their accuracy and range of validity should be examined. Particularly the presence of nozzles in the knuckle region complicates t...

Der Widerstand ungeschweißter und insbesondere geschweißter Bauteilbereiche gegen Ermüdungsschädigung erweist sich in Theorie und Praxis als ein komplexes Problem, für das methodisch und experimentell abgesicherte Auslegungsgrundlagen von exponierter Bedeutung im Sinne der technischen Anwendung sind. Die aus den ablaufenden Schädigungsprozessen abl...

The ACHEMA conference is an impressive exhibition on chemical apparatus engineering, closely connected with the epoch-making developments of chemical and process engineering. It is most timely to think about new opportunities of development. Large-scale plant engineering and general plant construction has experienced considerable improvement during...