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In this annual report of the project “Experimentally verified model based predictions for integrity of copper overpack” (PRECO2017) the status of the experimental and modelling activities and results has been summarised up to the end of January 2018. The testing program and related activities have been continued and partly modified to support the assessment and verification of the long term integrity of the protective copper (Cu-OFP) overpack of the canister. To consider more discontinuous uniaxial behaviour, creep tests with stepwise increasing load and stress dips were conducted, and the results were compared with those from normal constant load creep testing. In general, the transients especially from stepwise increase in loading can consume a part of the deformation capacity and shorten creep (or creep-fatigue) life. The relaxation testing programme has continued with cyclic relaxation tests. The relaxation testing aims at developing a relaxation model for the FE calculation. It is expected that with the relaxation model the stress and strain distributions will be different when compared to the FE results with a traditional creep model only. The results of continuing multiaxial (notched bar) creep testing program suggest notch weakening, or life reduction by tensile multiaxiality. The 10.000h testing of a CT specimen from the modified welding (FSW) process with argon protective atmosphere is complete and the specimen is going to be investigated by metallography to study the behaviour of the oxide particles.

The performance of materials in critical high temperature components of power and process plants is one of the major technical reasons limiting both the component life and process efficiency. New structural materials can be attractive in principle, but it has been challenging to simultaneously achieve good mechanical strength, oxidation resistance and cost-effective composition in the candidate alloys. The optimal material solutions for a given component depend on multiple factors, but one typical limiting factor is the waterside oxidation resistance at highest operating temperatures and pressures that extend to the supercritical (SC) or even ultra-supercritical (USC) range. To facilitate development of improved alloys for the new demanding applications, the methods of materials modelling can be useful to explore the effects of new ranges of chemical composition and fabrication routes. In the current paper oxidation modelling based on the concept of Cr and Ni equivalents is presented and applied to long term operation of superheaters made of nominally similar 11%Cr steel. The model quantifies the impact of the alloying elements on steam side oxidation to facilitate prediction of the oxide growth according to the alloy composition. The model can be used to predict the effect of variation of particular alloying elements, to explore the effects of alloying modification on performance for alloy development, and for life prediction when life is limited by water/steam side oxidation. The model prediction shows generally good agreement with the observed oxide layer thickness and also with prediction from conventional parabolic expressions when available for the alloy.

The paper highlights the practical aspects of new EU project SmartResilience and its application in Finland. The basic idea of the project is that modern critical infrastructures are becoming increasingly "smarter" (e.g. cities). Making the infrastructures "smarter" usually means making them smarter in normal operation and use, but it has to be checked if these smart critical infrastructures (SCIs) will behave equally "smartly" and be "smartly resilient" also when exposed to extreme threats, such as extreme weather disasters or, e.g., terrorist attacks. Similarly, the question is, if making existing infrastructure "smarter" is achieved by making it more complex, would it also make it more vulnerable? Would this affect resilience of an SCI as its ability to anticipate, prepare for, adapt and withstand, respond to, and recover? These questions are tackled by the project, which plans answer these questions in several steps: by (#1) identifying existing indicators suitable for assessing resilience of SCIs; (#2) identifying new "smart" resilience indicators (RIs) - including those from Big Data; (#3) developing a new advanced resilience assessment methodology based on smart RIs ("resilience indicators cube", including the resilience matrix); (#4) developing the interactive "SCI Dashboard" tool; and (#5) applying the methodology/tools in eight case studies, integrated under one virtual, smart-city-like, European case study. One of these case studies will take place in Finland, dealing with modern systems of energy supply.

Recurring waterwall leaks have been observed in a coal-fired boiler where subsequent inspections have shown through-wall internal oxidation, mostly at butt welds of 16Mo3 boiler tubes. In several cases the oxide had retained a thick pit plug even after local penetration of the tube wall. The original initiation site is no longer visible as it was removed by oxidation, but away from the most severe damage the internal oxidation appears to have initiated immediately downstream after a protruding weld root. This location, estimated oxidation rate and oxide appearance suggest that the mechanism is related to locally intensive heating in addition to flow turbulence. In the damage history of the same boiler wall, the first comparable leaks were recorded at shop welds with strongly protruding root shape, presumably inducing particularly strongly turbulent flow, and even then only after long term service. The most recent failures, however, occurred at normal repair welds or even within parent material, and after much shorter time in service. The characteristic features and causative factors of the tube failures are discussed in the paper, based on the available evidence and experience from operation and maintenance.

Steam driven turbogenerator units with size up to nearly 2 GW provide large fraction of the electric power in the world. Steam turbines may show good reliability, but their disturbances tend to be associated with significant cost so that preventive and corrective maintenance is generally easily justified. However, it is often not simple or convenient to implement repairs or replacements when unexpected damage is found at the time of opening the casing. This is because many turbine components are large in size or unique by design, and possibly only available from a limited number of suppliers and even then with a long lead time. Fortunately alternative measures can be often taken, and two types of steam turbine damage are considered here: steam erosion of inner casings and other stationary components subjected to flowing wet steam, and steam leaks of the main flange surfaces. From the user point of view, it may matter that much of the manufacturers' knowledge on turbines resides far away, partly because unlike some decades ago, the number of manufacturers in the world is now small. Together with low number of comparable machines, this may to some extent limit the local availability of expertise and experience for successful maintenance. It helps however that many features such as materials and operating conditions in steam turbines are not particularly daunting in the required knowledge accumulation, and that today the manufacturers may agree to offer help in the turbine maintenance regardless of the original manufacturer. Challenges may appear when outsourced turnkey maintenance implies shipping of major turbine sections or components to factory, to correspondingly extend the shutdown period because of the geographic distance involved, even if the maintenance project were to stay within schedule. It is demonstrated in the paper that successful on-site repair is often a viable and attractive alternative to conventional full repairs or replacements.

Risk-based inspection (RBI) has become common approach to support asset management in e.g. refineries, chemical industry in general and a few other industrial sectors. Although there are regionally established traditions to use RBI also in power plants, recently the interest has been spreading to include a widening base of common power plants. This is partly due to increasingly established standard practices, tools and availability of the techniques also for smaller scale users, and partly due to the generally established benefits and needs for safety and optimization of resources. In this paper we show how RBI was applied in a small scale for the main steam line of a CHP (combined heat and power) plant in Finland. The experience showed some typical features of initiating RBI, for example how important and beneficial (although at first somewhat tedious) it is to systematically gather and handle the required background information of design, fabrication, inspections, maintenance and operational history for RBI of an ageing plant. In the case of the example plant, the steam system had been significantly modified because of process changes, and the level of documentation was not equally thorough everywhere. Existing conventional guidelines and experience were found to be useful to support relatively lean RBI by suggesting typical areas of elevated probability of failure and therefore recommended areas to be inspected, for example at welds of large branches, locations of high strains in thermal system displacement or deviations in the function of the piping supports. Observed indications in the inspections were largely consistent with expectations and only resulted in repairs within the planned outage period. The resulting risk-based (or -informed) inspection and action plans are the main outcomes of the RBI exercise, aiming to produce the best justification and return on the maintenance investment, and to support safe operation and long-term lifecycle performance of the plant.

This report describes candidate resilience issues and indicators to be used when assessing, predicting and monitoring resilience of Smart Critical Infrastructures (SCIs). A total of 233 candidate issues and 1264 indicators are provided for various threats, SCIs and the five phases of the resilience cycle used in the SmartResilience project. Structured candidate issues and indicators are mainly provided by collecting existing issues/indicators from the risk, safety, security, crisis management, business continuity and similar domains, considering resilience as an "umbrella". The main intended reader is the person (user) - within a city or area, or a specific SCI - who is responsible for performing the resilience assessment, prediction or monitoring, including carrying out necessary calculations. This can be an in-house person performing e.g. selfassessment, or it may be an external assessor. The issues and indicators presented in this report and stored in the SmartResilience database are candidate issues and indicators. Each user is responsible for finding a relevant and complete set of issues and indicators for his/her own case study. The report may be used together with the SmartResilience methodology and the Guideline for assessing, predicting and monitoring resilience of SCIs developed in the SmartResilience project.

The report discusses the challenges posed by four types of threats -terrorist attacks, cyber attacks, extreme weather and social unrest- on the SmartResilience case studies. The way this analysis was conducted was by assessing these threats using a 5x5 framework matrix. The two axes of the matrix were phases (understand risks, anticipate/prepare, absorb/withstand, respond/recover, adapt/learn) and dimensions (system/physical, information/data, organizational/business, societal/political, cognitive/decision-making). Each individual matrix block was discussed by subject experts who identified specific challenges and implications for each matrix element and rated its relevance (high, medium, low). In terms of the results, the system/physical dimension received the highest number of important challenges. Overall, the most important singular element was to understand risks in the organizational/business dimension. The least importance was attributed to the adapt/learn phase.

Steam turbine is a rotating machine and therefore fatigue is an important damage mechanism to consider already in turbine design, and it is remains necessary to consider the risk of initiation and growth of fatigue cracks in the later in-service inspection and maintenance activities. With successful design and fabrication, and operation within the intended limits, the expected fatigue life is relatively long but nevertheless finite and variable. The design features and materials of steam turbine blades are generally well established, and conventional methods of inspection and maintenance are widely applied to monitor and limit the evolution of in-service damage. As the fatigue performance of a blade is simultaneously sensitive to material characteristics, structural/loading geometry and surface condition, the combined potential range of these factors explains in principle the observed wide scatter in turbine blade life. In this paper, examples on reduced blade life are discussed based on recent experience with a case example.

Power plant structures operating at high temperatures are designed for a lengthy explicit or implied minimum life, dictated by the expected life-consuming damage mechanisms like corrosion, creep, fatigue and other forms of wear and tear. The actually realised damage shows highest rates at locations of the most adverse combination of material properties (weakness e.g. in welds), loads (mechanical, environmental, thermal) and other features like geometry and deviations from the intended condition. In case of no additional surprises, the technically justified life is likely to nevertheless differ from the assumptions in design. The explicit or implied "safety factors" will offer on average some extended life and service potential to components even after operation up to and beyond the nominal design life. To avoid surprises, it remains wise be well informed of the evolving material and component condition of an ageing plant. The common questions are when and how should one measure to achieve the required confidence for decisions to run, repair or replace. In this paper we contemplate the challenges for managing the life of critical components of current and future power plants. Radical changes may happen in the merit order of plants by e.g. shifting fuel prices or public policies, and this could naturally affect the need, available budget and planning to maintain a given plant. Less impact is expected in the established principles of the technical operations like monitoring, inspections and interpretation of the results. However, changes are likely in selected areas related to materials and component lifing.

Storing solid fuels like coal in large quantity is known to involve a risk of spontaneous combustion. In comparison to conventional open stockpiles, closed storage may in principle decrease this risk by more limited ingress of air, but the risk can also be enhanced for example by reduced access for preventive or mitigating action. The risk of self-heating until ignition is considered here for a unique underground rock storage of a coal-fired power plant. The main adverse consequence of non-functioning storage is interrupted district heating that is more difficult to replace in winter than lost electricity supply. To predict the risk of spontaneous combustion with reasonable confidence, material modelling of coal properties has been applied with verification by comparison to actual field evidence. Fire risk management is discussed in terms of the available early warning indicators and options for cooling, extinguishing and prioritised use of stored fuel.

At high temperatures the water/steam side oxidation resistance is an important issue for boiler components like superheaters, where the growing internal oxide decreases heat transfer and increases surface temperature. This is increasingly critical for modern plants that aim for high efficiency from elevated levels of operating temperature and pressure. In this paper, a new simple model is presented to describe the steam/water side oxidation rate of common alloys for the high temperature end of the boiler plant. The model is based on the chemical composition of the alloys, applying equivalence expressions for collapsing the multi-variable problem to a more easily manageable setting with a combined parametric oxidation (POX) model. For verification, a range of experimental water/steam oxidation data from numerous tested alloys has been compared with the model predicted oxide growth. The results suggest a surprisingly good agreement with the model and test data. Although the optimised model parameters differ between e.g. steels and nickel alloys, as expected due to difference in the oxides, they remain very similar within a given material class, e.g. for all tested steels.

The advantage of using supercritical water (SCW) systems for power generation is based on the increased thermodynamic efficiency when operating at higher temperature and pressure. This has been realised for many years in medium to large size supercritical fossil plants. High efficiency in power generation is not only desirable because of economical reasons but also for enhanced environmental performance meaning reduced quantity of forming ash and emitted pollutants including CO2. Steam oxidation has become an important issue for steam power plants as operating temperatures increase from current to 650°C and even higher. To achieve these higher steam values new materials are needed. This paper presents results of the oxidation performance of potential new alloys (FeCrAlY, NiCrAl and Sanicro 25) in a supercritical water autoclave environment at 650°C/250 bar, with 150 ppb dissolved oxygen.

The research programme on the creep issues of the nuclear waste disposal canister copper material has continued with long-running uniaxial and multiaxial experiments as well as relaxation testing to support the material modelling activities, which produce appropriate material models to be used in the FE analysis, which will be used to assess the stresses and strains in the critical locations of the canister. The relaxation testing is ongoing and it has proven necessary to use a servo-mechanical testing machine in order to generate good quality test data. The initial FE prediction of strain rates calculated by the LCSP creep model and a relaxation model suggests a clear difference, but this needs to be verified after a better relaxation model is defined based on much more data. The most important result of this year has been the observation of cracking in the oxide particle zone at the friction stir weld root in the longest running CT test, which was terminated after 50 000 hours for sectioning and metallographic investigations. The oxide particles have nucleated creep cavities which have eventually lead to cracking of the oxide particle zone in spite of the low stress state 8 mm ahead of the notch tip. This observation is in line with the earlier results from uniaxial creep tests with a radial sample from the weld root. The weakness only manifests itself in long-term testing because the cavity nucleation and growth process is a slow process. Because of the low strength of the oxide particle zone welding in air should be avoided and vacuum or inert gas should be used instead.

Risk-based inspection (RBI) is not always applied in power plants that are generally not seen to carry similar safety and other hazards as e.g. some branches of the chemical industry. Hence the supporting standardization, industrial guidelines and available services for RBI activities have not been as well established in the power industry. Such support has been addressed for example in the European projects RIMAP, iNTeg-Risk and SafeLife-X, with results that include recommendations towards the evolving European standardization on risk-based assessments. This paper aims to explore the benefits of probabilistic life assessment in supporting RBI and related maintenance planning. The details in the input information, including the progression rates of the active damage mechanisms, will affect the associated uncertainty in the probability of failure, predicted minimum life, and the resulting conclusions on next inspections. However, successful probabilistic treatment of the input information can allow realistic treatments of the models for the indicated or postulated damage mechanisms, and by using for example Monte Carlo approach, the outcome prediction is not sensitive to the mathematical formulation of the individual or combined damage mechanism models. The examples have been selected from components subjected to high temperature service in applications where one can expect unavoidable damage accumulation in long term operation, and/or multiple mechanisms affecting the component life. Implications are discussed in terms of implementation in RBI and other aspects of managing the assets.

Hot steam lines operate at high temperatures and are designed against creep. In service they will consume the creep life at the highest rate in locations with the most adverse combination of material strength (weakness) and high stress (e.g. system loads). Adverse effects in stress state are promoted by features of geometry and discontinuities in the materials properties. In practice it is essential to find the areas of maximum damage, as these will determine the locations and timing to inspect and finally to repair or replace before failures or unplanned outages. The inspection experience from power plant steam systems have provided the established views on the expected locations of the early creep damage, and rules on timing the next inspection. The experience has also shown that optimal timing is materials dependent, and that the steel grade X20CrMoV11-1 (X20, 11% Cr steel) performs particularly well in the inspection statistics. This paper describes a case with observed creep cavitation and cracking in a branch weld of a X20 steam header that was replaced after 135 000 service hours. The characteristics of the observed damage and its evolution are discussed.

The high temperature sections of power and combined heat and power (CHP) boilers are designed for some de facto expected but finite life. Several significant damage mechanisms must be taken into account, particularly in superheaters and reheaters that are designed for creep but also suffer from thermal degradation, external erosion and corrosion, and internal steam oxidation that will gradually increase the metal temperature. As rising temperature tends to accelerate all damage mechanisms, major effects can be expected from the internal oxide growth. The feedback loop is taken into account in procedures to predict superheater life from known tube dimensions, time in operation, and other initial data. The oxide effect can be mitigated by internal cleaning, but in-service spallation of a relatively thick internal oxide can also become significant in old plants. Spallation can create problems but extends the tube life by keeping the wall cooler than with an adherent oxide. Examples are shown for boilers with more than 150 000 h of service.

Autoignition of coal in underground storage facilities is reviewed in the light of recent incidents of smouldering fires. The opportunities to prevent and extinguish closed-space fires are also considered considering the efficiency of the available alternatives. The challenges of such fires are highlighted by an example case, describing the observations and outcome of a smouldering coal storage fire. The principles of self-heating and most critical factors in spontaneous combustion such as the condition and quality of coal are fairly well known, but usually only provide partial help in fire prevention. The experience suggests that nitrogen injection can be useful for extinguishing controllable fires, while more extensive measures may be needed against uncontrolled fires. In general, efficient fire extinction during plant operation can be challenging, as any air ingress tends to feed the fire. Methods and indicators for predicting and detecting the ignition are discussed, and improvements are suggested to enhance the storage and plant availability. Also, new experience on dealing with frozen coal is discussed in brief.

Oxidation and corrosion of materials in highly demanding applications is critical for longterm performance of materials used in power generation. Energy production in biomass fired boilers is increasing rapidly due to the advantages of CO2 neutrality and renewability. Fluidised bed combustors and grate fired boilers have proved the most reliable technologies for burning biomass since its fuel characteristics are variable. The fly ash of biomass is relatively corrosive due to its composition containing high concentrations of chemically active compounds of alkali, sulphur and chlorine, and it also may contain erosive components especially in the case of fluidised bed boilers. Due to the potential for severe chlorine induced corrosion, plant operating temperatures and efficiency must be limited. To overcome material wastage more alloyed materials are needed. The high cost and sometimes hard to manufacture bulk materials could be replaced with coatings, which can be applied on the more economic low alloy steel having the proper mechanical properties. The paper discusses the benefits and limitations of thermal sprayed coatings in biomass boilers. The applied examples have included iron and nickel based HVOF and arc sprayed coatings subjected to verification field testing in boiler testing under in aggressive biofuel conditions. The coatings have shown good corrosion resistance in long-term field tests.

The combination of structural and materials performance together with the actual service conditions will determine the ideal timing for maintenance and the technical lifetime of gas turbine blades. While the designer aims to fit the process, structural and materials solutions together according to the foreseen service, some deviation is likely both in the manufactured components and in the actual service conditions. These deviations do not need to be large, as in particular a relatively small shift in local temperature can translate into large differences in life. The interest on the actual service temperatures often extends beyond the original supplier, but then the assumptions of design or original test data may not be available. Sacrificing one blade of a set for detailed inspection provides an opportunity to estimate the distributions of the effective service temperatures. In this paper, the principles of doing this are reviewed in brief, and few examples are given of evaluated blades. Although it is naturally possible that blades suffer from higher than expected thermal loads, quite often the evaluation will result in allowed life extension with or without refurbishment. The limitations of the approach are also discussed in brief.

Creep strain evolution plays a critical role in design and in life assessment of components subjected to service at high temperatures. For instance in turbines, boilers and steam pipes the recommended limits are 1% or 2% of strain. Unfortunately, straightforward engineering methodologies for predicting long term creep strain are not readily available. Robust methods for creep rupture extrapolation have been developed for example in the recommended procedures of the European Creep Collaborative Committee (ECCC) and PD6605 of BSI. The recently developed logistic creep strain prediction (LCSP) model transfers robustness into creep strain modelling. The LCSP model is directly linked to the rupture model and applies a small set of creep curve shape parameters to adjust primary, secondary and tertiary creep properties. The stress and temperature dependence of these shape parameters is optimised by fitting the available strain data. In this work the LCSP model was acquired for P22 steel from a small data set (max 3000 h) together with standard data for time to 1% strain. The model was then used to predict time to strain (0.5 to 5%) for two other P22 data sets using only true time to rupture. The model was also inversely applied to predict time to rupture from values of time to given strain for one of the data sets. The approach appears to be very competitive in spite of its simplicity, and is thought to hold considerable promise for e.g. creep modelling of new materials and welds, and when using FEA in creep analysis.

Structural analysis and lifetime assessment of steam drums in conventional power plants are discussed in this article. The analyses involve damage and structural mechanics, heat transfer analyses and fracture mechanics, and are connected to fluid mechanics. The used input data was from two steam drums in a Finnish fossil fuel power plant. Structural mechanics analyses were performed with FEM code ABAQUS. The lifetime analyses were performed using fracture mechanics analysis code VTTBESIT1.0. The primary considered damage mechanism was crack growth by corrosion-fatigue. Conclusions of the analysis results are summarised

Of the conventional time-temperature parameters (TTP's) for creep rupture, one of the most common is the Larson-Miller (LM) expression, which unfortunately predicts relatively inaccurate and optimistic values of extrapolated life. Some improvement can be expected by using better models such as the Manson-Haferd (MH) expression, which also can apply a low number of fitting constants, or other more complex standard models if there is sufficient data. However, similarly accepted models have not been standardised for creep strain data. In an example of constant stress creep data of 2¼Cr-1Mo (10CrMo9-10) steel, acceptable fitting of the time to given strain was obtained using a simple and robust modified MH model. The model involves four free fitting parameters, and provides a relatively good fit and an easier fitting procedure than a the more complex strain hardening model tested on the same data. Comparison to the standard creep strength of the 2¼Cr-1Mo steel suggests that the predicted long term creep strength from short term data of the example material tends towards increasingly optimistic values with increasing time and temperature. This difference appears more pronounced for time to rupture than for time to 1% creep strain, and is probably at least partly because the standard values originate from constant load testing with a systematically shorter time to rupture than under constant stress. The example involves a single data set, but demonstrates the need to avoid excessive extrapolation beyond the range of data. The conventional rule of maximum extrapolation up to three times the longest testing time is usually accepted for creep rupture. A somewhat more extensive extrapolation could be tolerated for the time to a modest strain up to about 1%

Gas turbines and particularly their hot path components exhibit relatively high maintenance cost and short in-service inspection cycles, in comparison with most main components of thermal power plants. The overall share of production capacity covered by gas fired combined cycle and CHP plants utilising gas turbines is still increasing, and the short inspection and maintenance cycles suggest corresponding strong growth for NDT services.NDT of gas turbine components is typically specified for three different purposes: within the shop during different phases of manufacturing or repairs, for user acceptance of new or reconditioned components, and for in-service assessment on the run/repair/replace decisions. The most demanding inspections in many ways are those performed in the field, as the available methods and access for the inspections can be fairly limited. Majority of the field inspections apply visual and surface techniques, but also ET and UT appear to find increasing use as they provide the potential advantage of indicating flaw depth. Examples are shown on in-service and ex-service inspections of hot end components, particularly turbine blades and vanes.

The mechanical and physical properties of engineering alumina ceramics (≥ 80% Al2O3) have been reviewed from literature data for the purpose of characterising the thermomechanical response of alumina to non-sintering manufacturing processes in engineering applications involving thermal cycles. Analytical expressions are given for temperature dependence where significant for the purpose of the work.

In order to quantify microstructural degradation at high temperatures, samples of SA 210 / AISI 304 L compound tube material were annealed in the temperature range 540 - 720°C for 1 to 1 000 hours. The hardness of the annealed material was measured and the microstructure of the samples was investigated with optical and scanning electron microscopy. Microstructural degradation was characterised by the carbide structure in the ferritic-pearlitic base material and by the depth of decarburised and carburised zones of the compound tube interface. The observed changes were quantified in terms of their time and temperature dependence and diffusion coefficients of the process. The results can be used in estimating the extent of thermal exposure of high-temperature components after long-term service or after incidences of overheating.

Thermal microstructural degradation was investigated by isothermal annealing of samples from boiler tube steels St 35.8, 15 Mo 3, 13 CrMo 44, 10 CrMo 9 10 and X20 CrMoV 12 1 in the temperature range 600 - 780°C for up to 2 000 h. Optical and scanning electron microscopy and hardness testing were used for characterising the microstructural changes and their time-temperature dependence. The results suggest a simple and consistent time-temperature dependence for all investigated materials, expected to apply also to long term service beyond the annealing time range of the present work. This would allow assessment of the in-service thermal exposure from the observed microstructure. A collection of micrographs has been prepared for this purpose, to aid in classifying and evaluating the observed microstructural state in terms of isothermal exposure to high temperature.

To indicate safe life or re-evaluation periods for high-temperature components, assessment based on measured creep cavitation damage is used worldwide. To interpret the observed damage unambiguously requires evaluation of the extent of damage on a unique, clearly defined and accepted scale. The presently available European damage scales in the guidelines NORDTEST NT TR 170 and VGB-TW 507 provide reference micrographs for a range of creep damage in the most common high-temperature steels. However, these guidelines differ in their stated and implicit definitions of a given class (extent) of damage, although both guidelines are nominally based on the same original Neubauer scale of creep damage.This work provides a comparison of the guidelines NORDTEST NT TR 170 and VGB-TW 507 guidelines, as well as an attempt to unify the European creep damage scales. The proposed unified definitions of damage are based on the quantified damage scales of NORDTEST NT TR 170 with limited revisions and simplifications. The new definitions for damage classification also aim to correct inconsistencies in the present guidelines, with minimum modifications to the actual example micrographs. The main use of the definitions is foreseen in constructing or extending compilations of reference micrographs on in-service damage, and in calibrating image analysis of such damage.

Ultrasonic testing is the main tool to inspect the structural integrity of primary circuit components in nuclear power plants (NPPs) during in-service inspection (ISI). In order to validate an inspection method and to train inspectors, reference flaws are needed. However, there are not enough real flaws available to be used for these purposes so artificial flaws must be used. Ultrasonic response from an artificial flaw must be representative enough so that it can be used as a reference flaw. Otherwise this could lead to a false result during an ISI. Unfortunately ultrasonic testing is highly dependent on the geometry of the component, the flaw type and the material in which ultrasound propagates. Therefore numerous flaws are needed to cover the probable flaw types, sizes and locations. The aim is to study artificial flaws and acquire wider knowledge on ultrasonic indications from artificial flaws in austenitic stainless steel weld and to compare them to the results from CIVA simulation. The study focuses on notches made by electrical discharge machining (EDM). EDM notches were chosen, since they represent a rough estimate of a crack type flaw and they are fairly quick and easy to manufacture.

Elastic pipe stress analyses are frequently performed to check that the stresses in pipe systems are allowed. For operation in the creep range such analyses may describe the stress distribution in the beginning but not after creep relaxation starts to take place. In the present work effects of creep are considered. A pipe system of P22 material that had been analysed by software for elastic analysis was also modelled for creep. By use of tabled creep data the following was studied: - Creep stress relaxation in the pipe system, - The effects of starts and stops on stress and strain distributions, - Creep in T-pieces with super imposed system stresses from the pipe system creep analysis. The creep properties of a virgin weld and a service exposed weld were determined by impression creep testing. The tests were performed in the parent metal, different parts of the HAZ and the weld metal. A weld was included in the model and analysed with these data. Resulting creep strain distributions from analyses with tabled and present creep test data were compared to each other and also to actual creep damage that was observed in components from the system.