EUROPEAN RESEARCH NETWORK AIMING AT HARMONISED PLANT LIFE PREDICTION PROCEDURES

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1 EUROPEAN RESEARCH NETWORK AIMING AT HARMONISED PLANT LIFE PREDICTION PROCEDURES R. Rintamaa a, I. Aho-Mantila a, L. Heikinheimo a, N. Taylor b a VTT Technical Research Centre, Finland b European Commission Joint Research Centre, The Netherlands address of main author: irina.aho-mantila@vtt.fi ABSTRACT The European Network of Excellence NULIFE (Nuclear Plant Life Prediction) has been launched with a clear focus on integrating safety-oriented research on materials, structures and systems and exploiting the results of this integration through the production of harmonised lifetime assessment methods. NULIFE will help provide a better common understanding of the factors affecting the lifetime of nuclear power plants which, together with associated management methods, will help facilitate extensions to the safe and economic lifetime of existing nuclear power plants. In addition, NULIFE will help in the development of design criteria for future generations of nuclear power plant. NULIFE was kicked-off in October 2006 and will work over a 5-year period to create a single organization structure, capable of providing harmonised R&D at European level to the nuclear power industry and the related safety authorities. While over half are from the research sector, NULIFE also involves many industrial organizations and, in addition to their R&D contributions, these take part in a dedicated End User Group. Joint research and development activity priorisation procedure and first pilot projects are defined. Led by VTT (Technical Research Centre of Finland), the project has a total budget in excess of EUR 8 millions. In Finland nuclear plant life prediction research is carried out in national nuclear safety programmes, today in SAFIR2010 programme, aiming at training of new scientists, linking and integrating international co-operation with the Finnish research as well. The main target is to maintain and improve knowledge needed for life management of the present power plants but also to be ready for the future needs. The SAFIR2010 programme is formed of eight areas where reactor circuit is one of the key topic consisting of research on: environmentally assisted cracking, structural integrity and monitoring of integrity. This work complements the research in European programmes. 1. THE VISION OF NULIFE Research and development to assess the service life of nuclear power plants is a multidisciplinary enterprise and must therefore take into account many factors. Lifetime assessment requires knowledge not only of the ageing of materials but also of factors such as load effects and reactor water chemistry and the influence of these on plant safety. Research data arising from this work has ultimately to be utilised for the development of safe and economic operation of existing nuclear power plants and the design of new units. NULIFE s 5-year vision is therefore to create a virtual institute with an integrated RTD platform embracing all European stakeholders within a completely new structure with improved and efficient use of public and private RTD funding. It will provide the European nuclear power industry and national regulatory authorities with information and methods to 1

2 assess the service life of nuclear power plant materials and structures, as well as to underpin strategies for upgrades or refurbishment. In particular, NULIFE will serve to support the harmonisation of lifetime assessment methods and practices for nuclear power plants throughout Europe. Best practices for the prediction of life time of reactors or systems will support strategic management in the decisions on upgrading the plant. The path towards the vision is described in Figure 1, proceeding through different phases of integration evolution and finally reaching NULIFE Institute with customer-driven programme. [1] Major milestones 12 months 36 months 24 months 60 months 48 months Beyond 5 years Consolidation of integration plan Preparation of business plan Integration plan NULIFE Institute with customer-driven programme Transition plan for permanent entity Creation of Virtual Institute Structure with permanent entity features Joint use of facilities Investment policy Launching of new RTD projects Development and application of procedures and best practices Business plan, Updated structure Links with national programmes Approaches to training, knowledge and comm. Viable expert groups Coherent structure Communication methods Permanent management structure Long term business plan Acknowledged solution provider Past Networking activities Key integration indicators FIG. 1. Planned organizational evolution during the five phases of NULIFE ( ). 2. THE UNIQUE CONSORTIUM OF NULIFE The core of the network comprises ten leading research institutions, technical support organizations and industrial enterprises from across Europe. Key organizations, Contractors of NULIFE are VTT, Technical Research Centre of Finland, a Coordinator of NULIFE Studiecentrum voor Kernenergie - Centre d'etude de l'energie Nucléaire, SCK CEN from Belgium Ustav jaderneho vyzkumu Rez a.s., Nuclear Research Institute Rez plc, NRI from Czech Republic Commissariat a L'Energie Atomique, CEA and Electricité de France, EdF from France AREVA NP GmbH from Germany European Commission Directorate General Joint Research Centre, JRC, from The Netherlands British Energy Generation Ltd and Serco Ltd from UK and Forsmark Kraftgrupp AB from Sweden. The contractual arrangement is shown in Figure 2. The ten core organizations (contractors) are signatories to a Consortium Agreement, which defines the working arrangements and 2

3 decision-making procedures in NULIFE. They are supported by the contributions of 27 organizations (Table 1) from industry and research, which contractually act as third parties under the full responsibility of contractors. Contract EU/EC Consortium Agreement VTT SCK CEN NRI CEA Electricité de France AREVA NP GmbH JRC British Energy Generations Ltd Serco Ltd Forsmark Kraftgrupp AB Collaboration Agreement Collaborators (NN) Associate Agreement Associate Contributors (27) FIG. 2. The unique contractual structure of NULIFE consortium with third parties, so called Associate Contributors. The third parties support this in several important ways: Provide a sufficiently broad representation of European nuclear countries and stakeholders to allow NULIFE to achieve its consensus/harmonisation objectives Contribute technically to investigation of priority issues and to assessment and benchmarking of proposed procedures, leading to their broad acceptance Contribute to the network's knowledge base of expertise and data from existing R&D programmes Provide an in-built mechanism for effective dissemination, both in terms of ensuring rapid uptake of proposed procedures as well as substantially extending the contact base of the network at national and regional level Increase the participation of PhD students and young professionals and widen the training base Provide increased options for mitigating possible changes to the consortium organization Reinforce the influence of NULIFE at wide international level as being European Network/Centre of Excellence A Collaboration Agreement mechanism is also applied whereby additional organizations can take part in specific activities on a discretionary basis but without any reimbursement of costs. This is intended mainly to facilitate the participation of utilities and other external stake-holders in the End User Group. The EU funding (EUR 5 million) is specifically targeted at a process of integration between the contributing research institutions and ensuring the long-term sustainability of the network. 3

4 Table 1. Organizations participating in NULIFE as Associate Contributors. Associate Contributors Country Institute of Metal Science - Bulgarian Academy of Sciences Bulgaria AREVA NP SAS France Institut de Radioprotection et de Sureté Nucléaire France Fraunhofer Institute for Mechanics of Materials Germany Forschungszentrum Dresden Rossendorf e.v Germany Gesellschaft für Anlagen- und Reaktorsicherheit mbh Germany Universität Stuttgart Germany Bay Zoltán Foundation for Applied Research Hungary AEKI Atomic Energy Research Institute Hungary Lithuanian Energy Institute Lithuania Nuclear Research & Consultancy Group The Netherlands Centro de Investigaciones Energéticas Medioambientales y Spain Tecnológicas Institute For Nuclear Research Pitesti Romania Center of Technology and Engineering for Nuclear Projects Romania Vattenfall Research and Development AB Sweden Tecnatom, S.A. Spain Paul Scherrer Institut Switzerland Rolls-Royce Power Engineering PLC UK The University of Manchester UK Josef Stefan Institute Slovenia E.ON Kernkraft GmbH Germany ENEL Produzione S.p.A Italy Oskarshamm KG AB Sweden Studsvik Nuclear AB Sweden Westinghouse Electric Sweden AB Sweden Siempelkamp Pruef- und Gutachter-GmbH Germany Ringhals AB Sweden 3. ORGANIZATIONAL STRUCTURE OF NULIFE The main organizational elements of NULIFE (Figure 3) are as follows: Governing Board is the ultimate decision-making body of the Consortium and consists of one nominated representative of each contractor. Nominated representatives of the associate contributors also have the right to participate to the Governing Board meetings as observers. Executive Group is responsible for the execution of the agreed work programme and comprises nominated representatives of the Work Package (WP) leader organizations. Infrastructure Group (a sub-group of the Executive Group) develops common platforms for network administration, for experimental testing and investigations, for simulation and analyses, for data management, documentation and software tools. Expert Groups provide a mechanism for coordinating and integrate the available expertise of the researchers nominated by each of the participating organizations, for supporting the research projects and for developing advanced technical methods; the Expert Groups may have sub-groups dedicated to specific technical areas. 4

5 End User Group is composed of representatives of participating utilities, other endusers and manufacturing industry; its role is to give advise on concerning research directions and to select and propose the research priorities together with the NULIFE Executive Group. NULIFE Governing Board Chair J-P. Hutin EdF Management Contractors, Associate Contributors, Collaborators Expert Groups 1) Materials and materials ageing 2) Integrity assessment 3) Lifetime evaluation 4) Safety, risk information and reliability Executive Group Chair R. Rintamaa VTT Infra Group R&D infra End User Group R&D strategy R&D projects Regulators National and international networks/projects/ organisations FIG. 3. The main interactions between organization groups and the cross-cutting work packages. The work programme (referred to as the Joint Programme of Activities or JPA) consists in a series of work packages (WPs), which are clustered in three main areas: integrating activities; R&D support activities and spreading excellence activities (including training) (Figure 4). 5

6 Integrating IA-3 (NRI) Knowledge management IA-5 (JRC) Harmonisation IA-2 Expert Groups - Materials (SCK CEN) - Integrity (ANP-G) - Lifetime (SERCO) - Safety & risk (FKA) IA-1 (VTT) Mapping of partner RTD expertise IA-4 (CEA) Key facilities IA-7 (VTT) Integration planning IA-6 (VTT) Business plan RA-1 (BE) Road Mapping of RTD priorities RA-2 (EDF) End users priority for new projects Management Activities Coordinator VTT Joint R&D RA-3 (SCK CEN) Stress Corrosion Cracking RA-4 (EDF) Thermal Fatigue SA-1 (VTT) Website and communication platform SA-2 (JRC) Reporting and publications SA-3 (SCK CEN) Education, training and dissemination SA-4 (JRC) Partner projects and networks Spreading SA-5 (CEA) Links to regulators FIG. 4. Joint Programme of Activities including Integrting Activities (IA), Joint Research and Development Activities (RA), Spreading Excellence Activities (SA) and Management Activities (MA). 4. EXPERT GROUP ACTIVITIES NULIFE brings together a broad range of scientific and technical competences, facilities, tools, data, operating experience and organizational skills which must be effectively integrated into the network structure and work programme (Figure 4). An important first step is therefore to perform a comprehensive mapping exercise. As a result of this complementary and overlapping resources will be identified, together with any gaps that have to be addressed. The NULIFE questionnaire for mapping expertise has been launched. Research organizations and service providers are asked to define the current expertise, and end users and vendors are asked to define strategic needs. This covers different reactor types, experimental conditions, system and component types as well as material types. Life management expertise is broken down into areas such as degradation modes, load effects, condition monitoring, inspection, integrity assessment and safety management. Testing facilities, organization/process related expertise, dissemination skills as well as design, manufacturing, operation expertise are also all being considered. The coordination of the network's combined expertise is managed principally via a system of Expert Groups covering the following generic technical areas: Materials Expert Group (EG1) deals with the material property issues, in particular the mechanisms of materials degradation (Environment Assisted Cracking, thermal ageing, irradiation embrittlement) and characterization of the properties of aged materials, i.e. as a function of in-service conditions. Integrity Expert Group (EG2) is concerned with establishing state-of-the-art in methods and tools for of assessing potential damage or failure modes. It deals not only 6

7 with fracture mechanics methods, but includes also a consideration of existing Codes and Procedures, Non Destructive Examination, safety factors and certain special topics (effects of load history, crack arrest, secondary and residual stresses, WPS). In Lifetime Expert Group (EG3), the knowledge gaps identified by the other expert groups will be assessed in terms of their implications for through-life structural integrity. In addition, an assessment will be made of the potential for, and possible implications of, knowledge gaps outside the scope of the other expert groups. Lifetime Expert Group will take a long-term perspective of component integrity, in particular the safety justification of components over the whole of their foreseen operational life, where the demonstration of safety margins becomes dominated by considerations of fatigue (including thermal fatigue and corrosion fatigue), irradiation embrittlement and other ageing processes (including creep and creep-fatigue). Safety Expert Group (EG4) will add to other Expert Groups to support the Network by providing advice on identification, characterisation and management of uncertainties in lifetime evaluation, through modelling structural reliability and performing risk assessments to provide added insights into the assessment of safety margins. The researchers named by the participated organizations are allocated to one or more of the Expert Groups (Figure 5). Each group is lead by a Contractor organization and is coordinated by a committee representing the main technical interests. Their principal tasks are: plan and implement a strategy for developing NULIFE s technical expertise in the relevant area planning and execution of R&D and harmonisation projects, via teams selected from the EG s pool of expertise support horizontal network WPs such as expertise mapping, knowledge management, training, dissemination etc. Each EG may have sub-groups dealing with specific technical topics. The EG coordination committees meet at network meetings, but sub-groups on may hold separate meetings. Partner 1 Partner 1 Partner 1 Partner 1 Partner n Organisations participate in NULIFE with a group of named researchers EG1 Materials EG2 Integrity EG3 Lifetime EG4 Safety Researchers contribute to the permanent Expert Groups, which may each have several discipline-specific sub-groups Each EG has a Leader and a coordinating committee; these meet at the network meetings R&D Project R&D Project R&D Project Researchers from the EGs contribute to specific R&D projects of fixed duration SMIRT August 12-17, 2007 Toronto, Canada FIG. 5. NULIFE s Expert Group system for integrating the efforts of the researchers nominated by the participating organizations. 7

8 5. RESEARCH AND DEVELOPMENT PLANNING Effective developing R&D projects to meet stakeholder needs is essential to NULIFE s strategy (Table 2). The network work programme therefore has a dedicated work package (RA-1 R&D Road Mapping) that is tasked toset up and implement a systematic and clear process for identifying necessary research topics for NULIFE, define the necessary work programmes and make recommendations to the Executive Group for implementation. Table 2. The End User Group s preliminary identification of research topics and application areas. Reactor pressure vessel Internals Reactor coolant system Connected lines Steam generators Thermal fatigue (Pilot) X X X Stress corrosion cracking (Pilot) X X X Welds and repairs X X Clad properties and ageing X Safety factors / uncertainties X X X Stress classification X The interest shown by the End User Group for stress corrosion cracking and thermal fatigue lead to these topics being chosen as the two pilot R&D projects. The respective goals are as follows: The stress corrosion cracking pilot project will exploit the results from relevant national programmes in which NULIFE members participate, by an information sharing process involving both the contractors and third parties. The deliverables will be an integrated database on environmental assisted cracking (EAC) of light water reactor materials, together with best practice guidelines on EAC testing. The thermal fatigue study will exploit results from recent international and European projects. Its main tasks include: Complete the validation database for thermal stratification and thermal striping type damage Extend the knowledge base on thermal hydraulic boundary conditions for high frequency loading in mixing zones of piping including probabilistic aspects Extend the assessment procedure and review the best practice in predicting fatigue damage accumulation using both phenomenological criteria and proper material modelling and also provide recommendations for fatigue crack growth Provide recommendation on fatigue curves, including implicit or explicit consideration of environmental effects By providing research excellence and fostering common approaches in nuclear power plant lifetime prediction, NULIFE will contribute to the Electric Power Utilities decision making in terms of plant operation and investments. Safety Authorities will also benefit from the knowledge in their duties to grant plant licenses for the continued operation of plants. The ability of the network to deliver procedures and best practices documents on ageing issues will be an important measure of the network s impact. At the highest level, NULIFE will support the development of a European Common Safety Justification Framework. Since lifetime management tools are only one element in such a framework, its development will require support from other stakeholders than R&D organisations. The broad composition of the network is a major advantage in this respect. 8

9 NULIFE will also benefit from other European and national activities, collected and communicated widely in R&D forums. In the scope of the NULIFE new joint projects are being identified and prioritized to meet futur trends and needs. The launch of such projects will occur in the near future depending on priorities and funding arrangement. 6. NATIONAL RESEARCH PROGRAMME SARIR 2010 In Finland nuclear plant life prediction research is carried out in national nuclear safety programmes, today in SAFIR2010 programme, aiming at training of new scientist and linking international co-operation with the Finnish research as well. The Finnish Research Programme on Nuclear Power Plant Safety, SAFIR2010, has been planned for the years [2]. In 2007 there are altogether 30 research projects. The total volume of the programme in 2007 is planned to be approximately 46 person years and 6.3 M. The objective of the national nuclear safety research programme, SAFIR2010, is to ensure that new matters related to safe use of nuclear power plants appearing, the public authority has sufficiently such technical and other faculties that the importance of these matters can be determined without delay. High scientific quality is required of the research projects in the programme and their results have to be published. The usability of the results are not restricted to power plants of only one licence holder. The planning period for the national research on nuclear power plant safety up to 2010 contains granting licences for the Finnish power plants in use and that under construction or the overall evaluation related to licence conditions: The operating licence of plant units Loviisa 1 and 2 will be renewed and the periodic safety review included in the operating licence conditions of the plant units Olkiluoto 1 and 2 will be implemented. Operating licence will be applied for the plant unit Olkiluoto 3 that is under construction. These processes are reflected in many ways in the national safety research. SAFIR2010 research programme is divided in eight research areas that include both projects in their own area and interdisciplinary co-operational projects. The areas are: Organisation and human factors Automation and control room Fuel and reactor physics Thermal hydraulics Severe accidents Structural safety of reactor circuit Construction safety and Probabilistic Safety Analysis (PSA). The biggest area is Structural safety of reactor circuit (23% of total volume), projects planned for 2007 are summarised below: Risk-Informed Inspections of piping: The overall objective of the project is to support the implementation of risk-informed in-service inspection (RI-ISI) at Finnish nuclear power plants by studying relevant issues related to RI-ISI. Main objectives are the development of structural reliability methods for quantification of piping leak and break probabilities, the development of methods for evaluating inspection capability and the link between inspection qualification, detection probability and RI-ISI, and studying issues related to risk-ranking, selection of inspection sites and acceptance criteria of a RI-ISI programme. 9

10 Fatigue endurance of critical equipment: The project aims to improve and verify models used for assessment of fatigue endurance and failure probability of nuclear reactor pressure boundaries and critical components used in power machinery. Quantitative, mechanism based and risk informed probabilistic evaluation of fatigue crack initiation (and short crack growth) due to thermal and/or mechanical loads is aimed, but compatibility with the existing design codes need to be maintained. Water chemistry and oxidation in the primary circuit: The objective is to study how different water chemistry conditions affect the oxidation rate of different fuel cladding materials, the decontamination procedures available at the moment and options for chemistry conditions in these processes, pre-oxidation of component and system surfaces, which can have a crucial effect on the corrosion rate and activity incorporation onto the surfaces.the fourth objective is to evaluate the effect of dissolved H 2 on the stability of the oxide films on nickel-base alloys and their weldments during cool-down of a PWR. Monitoring of the structural integrity of reactor circuit: The aim of this project is to develop techniques and monitoring systems that can be used to monitor the structural integrity of the primary circuit components. The aim is to develop measurement systems both for detection and analysis of macroscopic flaws and microscopic changes in the material that are often preceding the macroscopic failure. In 2007 the basics for the design of monitoring system will be studied. It is also necessary to develop inspection techniques that can be applied to reactor circuit components where the access is restricted and decreasing the reliability of inspection. This kind of inspection items are e.g. welds with coarse grain size and nozzle welds where the difficult geometry is restricting the performance of inspection. Fracture assessment for reactor circuit: The objectives for fracture risk assessment comprise (i) calculation of design and unforeseeable loads and their effects on a structure by applying numerical modelling; (ii) development of advanced fracture mechanics assessment tools and analysis methods based on material characterisation, damage mechanisms models and structural performance, in order to control structural failure both in cases of postulated initial flaw and environmentally assisted (internal) material damage; (iii) determination of degradation in material properties during service. Influence of material, environment and strain rate on environmentally assisted cracking of austenitic nuclear materials: The project aims to increase the understanding of environmentally assisted cracking (EAC) mechanisms in austenitic nuclear materials by identification of precursor events for EAC. The role of deformation mechanisms and localisation of deformation in EAC of deformed, non-sensitised stainless steels, nickel-based materials and their weld metals as well as irradiated stainless steels are investigated in depth during the four year project. Investigations are performed on different types of materials as a function of cold work, environment (BWR and PWR) and strain rate. Crack initiation investigations are carried out on stainless steels during the first year, continued on nickelbased materials and their weld metals during the second and partly third year and on irradiated stainless steels during the third and fourth year. The role of dynamic strain ageing and localisation of plastic deformation on EAC of nickel-based materials is studied within an ongoing thesis work. The influence of strain rate and environment on the fracture toughness properties of austenitic nuclear materials are also measured during the first year. The latest international knowledge is brought to Finland by participating in international co-operation within the field of EAC and irradiation assisted stress corrosion cracking (IASCC). Interaction and challenges of the Structural safety of reactor circuit projects are presented in Figure 6. Projects are supported by advanced facilities for materials ageing testing in simulated nuclear environments and Hot-Cells for irradiated materials testing. VTT s Quality Management 10

11 System is certified according to ISO 9001:2000 by Lloyd s Register Quality Assurance. Destructive and non-destructive testing and chemical analysis method have been accredited by FINAS (Finnish Accreditation Service). FIG. 6. Challenges in the management of reactor circuit structural safety. 7. FUTURE TRENDS The main technical issues that are likely to be important for lifetime management in the future are to gain a better physical understanding of ageing related damage mechanisms, to develop qualified methods for detection, surveillance and control of degradation and to develop predictive models and analysis tools. For plant life management, analyses must show that the plant will continue to operate within its design basis. Where a change in operation is desired there will be a need for safety analyses to cover the new operational conditions. The future challenges need to have an adequate knowledge of the current design basis of the plant, to have a correct picture of the actual state of the plant and to define the analyses needed to support long-term operation within its design basis. This requires relevant and qualified generally accepted data bases and methodologies. Risk-informed and PSA methods will be increasingly used, e.g. to identify any excessive risk contributors, to evaluate relative significance of safety issues arising from deterministic reviews, to help prioritise corrective actions and to evaluate the effect of proposed plant or procedural modifications. Current ISI programmes are based on experience feedback and engineering judgements through a deterministic analysis. In future, more use of probabilistic safety analysis (PSA) is needed for planning of ageing management programmes. In addition, studies are underway for development of alternative methodologies for proposing an ISI programme which is in compliance with the required safety level. Periodic Safety Review 11

12 (PSR) will play an important role in future in reviewing the viability of R&D and industrial infrastructure to support safe NPP operation. Due to the current boundary conditions in the educational system, there is concern that in the future there will be less possibilities to recruit qualified personnel with knowledge from specialised vocational education. At the European level a well defined structure for training should be established. Further development of the so-called Eurocourse, offered by a consortium of organizations and covering all safety related aspects for pressure-retaining components during operation of nuclear power plants, should be continued. Lifetime management, being a multidisciplinary process, creates a strong need to navigate, share and integrate the existing knowledge as well as to co-ordinate the initiation of new R&D activities in the international level. Future form of networking, NULIFE as an example, need to exploit the experience of the running networks which provide an excellent forum for specific areas. In addition to such present activities, more emphasis is needed on qualification in all relevant technical disciplines and on effective knowledge management important to PLIM. 8. CONCLUSIONS The European Network of Excellence NULIFE (Nuclear Plant Life Prediction) has been launched with a clear focus on integrating safety-oriented research on materials, structures and systems and exploiting the results of this integration through the production of harmonised lifetime assessment methods. The NULIFE activities started in 2006 and the goals for the five first operating years are NULIFE network of excellence will form an integrated RTD platform, embracing all stakeholders at European level. NULIFE aims to improve the delivery to end-users of best-practice life assessment methods to support optimized ageing management programmes for existing nuclear power plants and also to new builds NULIFE intends to use of public and private RTD funding in an optimized way to launch new projects. NULIFE will also benefit from other European and national activities, collected and communicated widely in R&D forums. ACKNOWLEDGEMENTS NULIFE Executive Group members Milan Brumovsky (NRI), Peter Budden (British Energy), Stephane Chapuliot (CEA), Claude Faidy (EDF), Göran Hultqvist (Forskmark), Elisabeth Keim (Areva NP GmbH), David Lidbury (Serco Assurance), Steven Van Dyck (SCK CEN) are gratefully acknowledged for their contributions. SAFIR2010 Steering Committée is acknowledged for the programme description. REFERENCES [1] NULIFE - Nuclear plant life prediction ( (27 June 2007). [2] SAFIR The Finnish Research Programme on Nuclear Power Plant Safety ( (27 June 2007). 12