Recent activities and results of the Nuclear Energy Agency (NEA) Working Group on Integrity and Ageing of Components and Structures (WGIAGE)

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1 Recent activities and results of the Nuclear Energy Agency (NEA) Working Group on Integrity and Ageing of Components and Structures (WGIAGE) Olli Nevander Nuclear Safety Specialist, NEA Jürgen Sievers Chief Expert on Structure Mechanics, GRS 4 th International Conference on NPP PLIM, Lyon, France SESSION 3-8; 26 October Organisation for Economic Co-operation and Development

2 The NEA: A Forum for Co-operation for the Most Advanced Countries in the World Founded in member countries 7 standing technical committees 75 working parties and expert groups 18 international joint projects and 4 database projects Organisation for Economic Co-operation and Development 2

3 The NEA Mission To assist its member countries in maintaining and further developing, through international co-operation, the scientific, technological and legal bases required for a safe, environmentally friendly and economical use of nuclear energy for peaceful purposes. To provide authoritative assessments and to forge common understandings on key issues, as input to government decisions on nuclear energy policy, and to broader OECD policy analyses in areas such as energy and sustainable development Organisation for Economic Co-operation and Development 3

4 OECD/NEA Membership Australia Austria Belgium Canada Chile Czech Republic Denmark Estonia Finland France Germany Greece Hungary Iceland Ireland Israel Italy Japan Korea Luxembourg Mexico Netherlands New Zealand Norway Poland Portugal Russia Slovak Republic Slovenia Spain Sweden Switzerland Turkey United Kingdom United States OECD and NEA member OECD member, not NEA NEA member, not OECD 2017 Organisation for Economic Co-operation and Development 4

5 Organisation for Economic Co-operation and Development 5

6 Current Officers WGIAGE Chairman: WGIAGE Vice-chair: Jürgen Sievers (GRS) Carlos Castelao (CSN) Metal Sub-Group Chairman: Metal Sub-group Vice-Chair: Concrete Sub-Group Chairman: Concrete Sub-Group Vice-Chair: Seismic Sub-Group Chairman: Seismic Sub-Group Vice-Chair: Robert Tregoning (NRC) Björn Brickstad (SSM) François Tarallo (IRSN) Pekka Välikangas (STUK) Nebojsa Orbovic (CNSC) Emmanuel Viallet (EdF) WGIAGE Secretariat: Olli Nevander (OECD NEA) Organisation for Economic Co-operation and Development 6

7 Structure and activities of WGIAGE The WGIAGE consists of a main group and three subgroups dealing with: a) integrity and ageing of metal structures and components; b) integrity and ageing of concrete structures and; c) seismic engineering. The WGIAGE group started its annual meetings in year During years the WGIAGE published totally 8 technical reports. In year 2017 totally 15 international activities are going on in the WGIAGE Organisation for Economic Co-operation and Development 7

8 WGIAGE main group's activities 1. Continuous work in coordinating the long term operation research with the goal to collect and identify current experience and assess areas for further improvement on plant ageing management at the member countries. The recent result of the work was the published report: NEA/CSNI/R(2015)13, Questionnaire on Long- Term Operation of Commercial Nuclear Power Plants, with recommendations on new research activities in the area; 2. The activity on behaviour of components and structures under severe accident loading (COSSAL) includes a couple of benchmark studies for PWR and BWR plant types. The objective of the ongoing COSSAL work is to compare structure mechanical analysis methods for integrity assessment of metallic components of selected pressurized and boiling water reactors under severe accident loading. In the end of COSSAL activity there will be a final Workshop on February General working subject of groups to identify research and development areas with common interest of members related to age-related degradation of materials in safety-related systems, structures and components (SSCs). Main group also coordinate and review the activities of its three subgroups Organisation for Economic Co-operation and Development 8

9 Structure and activities of metal subgroup The subgroup finished a project on the effects of ageing and embrittlement on the structural integrity of the reactor pressure vessel (RPV) entitled, Probabilistic Structural Integrity of a PWR Reactor Pressure Vessel (PROSIR) - NEA/CSNI/R(2016)12. The subgroup arranged the Fourth International Conference on Fatigue of Nuclear Reactor Components, 28th September-1st October 2015 in Seville, Spain. The Proceedings were published - NEA/CSNI/R(2017)2 in The benchmark on the analytical evaluation of the fracture mechanic parameters K and J for different components and loads was finished with the summary report NEA/CSNI/R(2017)11. Benchmark work on analyses of Leak-Before-Break (LBB) in piping systems has started in Within the LBB benchmark activities the application of national requirements for LBB into the cracking analysis will be compared. Further the effect of the primary water stress corrosion cracks (PWSCC) will be studied. The workshops and reporting will follow in years 2018 and The activity on evaluation of design and monitoring requirements for vibrations in safety related piping and reactor pressure vessel internals is looking for limits, requirements and operating experiences in member countries. The result report of the activity will be published in Organisation for Economic Co-operation and Development 9

10 Ongoing activities of concrete subgroup The concrete subgroup of WGIAGE is steering a project on ageing of concrete, entitled Assessment of Structures subject to Concrete Pathologies (ASCET). This project was initiated in A prior project in this area resulted in the report: NEA/CSNI/R(2015)5, entitled Bonded or Unbonded Technologies for Nuclear Reactor Pre-stressed Concrete Containments. The ASCET project is reporting its second phase and starting its third phase in The first phase results are reported in detail in a published NEA report /NEA/CSNI/R(2016)13/. The ASCET-project is providing recommendations for ageing management of nuclear facilities subject to concrete degradations with a focus on alkali-silica (aggregate) reaction (ASR). The benchmark activities on Improving robustness assessment of structures (IRIS) are now in phase 3. The first two phases of IRIS activities are published in: /NEA/CSNI/R(2014)5/ and /NEA/CSNI/R(2011)8/. The IRIS benchmark activities are based on experiments with different missiles (ca. 50 kg) impacting reinforced concrete slabs. The tests have been/are performed at the VTT, Finland. The results are providing new information which is useful for the validation of analysis methods to be used for the assessment of airplane crash scenarios Organisation for Economic Co-operation and Development 10

11 Ongoing activities of Concrete subgroup Activities on pre-stressed concrete reactor containment behaviour in test conditions taking into account ageing effects have been started in The activities include various benchmarks based on test programs at the French 1/3 scaled containment test facility VERCORS (see Figure 2). Presently a VERCORS benchmark is going on and results are expected in March A workshop on VERCORS benchmark results will be arranged in Saclay, near Paris in August >>>> An activity for comparing the probabilistic and performance-based methods in reassessment and design of building structures in nuclear facilities in member countries is going on. The resulting report of this activity will be published in About 21 meters high VERCORS facility: an experimental mock-up of a reactor containment-building at 1/3 scale has been built at EDF Lab Les Renardières near Paris (France). Source: VERCORS webpage Organisation for Economic Co-operation and Development 11

12 Ongoing activities of Seismic subgroup a) The activity on quantifying the existing margins in seismic analysis of safety class components for high seismic loads associated with existing design practices within a benchmark activity (MECOS) is in reporting phase. The MECOS activity is developing new design and analysis methods and standard provisions for fatigue ratcheting in the case of seismic events. The final report on results including the benchmark and workshop descriptions will be published in A piping system for the shaking experiments in Bhabha Atomic Research Centre, Mumbai. Tests were carried out by the Central Power Research Institute (CPRI) of Bangalore, India. Test results were used in the MECOS benchmark Organisation for Economic Co-operation and Development 12

13 Ongoing activities of Seismic subgroup b) The activity on developing methodologies to assess the robustness of NPP structures against Safe Shutdown Earthquake (SSE) with on-site observations and measurements is in the reporting phase. The information used in this activity is collected in member countries during earthquake events in the sites. The activity will be reported in c) The benchmarking activities on the seismic capacity of reinforced concrete shear walls (CASH) are now in the second phase. In this phase, the capacity of a full scale shear wall extracted from a NPP building is assessed with various seismic loading intensities (pushover, cyclic and dynamic analyses). The results of the work will be reported end of d) Seismic hazard assessment is a major concern in many member states because of the uncertainties that are generally attached to these assessments. Therefore the subgroup has an activity on making a comparison study of Probabilistic Seismic Hazard Analysis (PSHA) in areas with low, medium and high seismic activities. This concept of PSHA testing is targeting for the reduction of uncertainties. The results of PSHA activity will be reported and published in Concurrently comparisons of PSHA outputs between areas with high activity and low-medium activity are planned to be carried out based on the activity results. Together with the ongoing activity Methodology development for improved assessment of SSE robustness against on-site observations these two activities are trying to reach better understanding and possible harmonization of different approaches and methods to estimate the effects of seismic hazards in nuclear design Organisation for Economic Co-operation and Development 13

14 Challenges and plans of WGIAGE The following general targets could be seen for the work in WGIAGE in future: 1. Less uncertainties in design codes taking into account the operating and field experiences in updating and defining new code requirements, 2. Consider potential degradation due to operating conditions and ageing as early as possible in the design process, 3. Integrate Ageing Management Program including inspections, degradation analysis, surveillance and preventive actions into the Design and Operation Codes Organisation for Economic Co-operation and Development 14

15 Identified possible new activities of metal subgroup a) Ageing of reactor pressure vessel internals and embrittlement of the reactor pressure vessel b) Environmental effects on metal fatigue c) Non-destructive Examination (NDE) implementation programs and strategies for selecting components to be inspected d) Weld Residual Stress (WRS) simulation and treatment in structural integrity analyses. e) The role of secondary stresses in fracture assessments Organisation for Economic Co-operation and Development 15

16 Identified possible new activities of concrete subgroup a) Tests with concrete samples from decommissioned NPP Gentilly 2 (Canada) b) Code comparison for determination of shear capacity and sizing of building structures c) Start activities related to ensuring the quality management and updating procedures in use of three dimensional Building Information Modelling (BIM) in design, construction and operation of nuclear facilities during their lifetime d) Ageing of concrete structures in waste storage facilities Organisation for Economic Co-operation and Development 16

17 Identified possible new activities of seismic subgroup a) Activities to provide new information into the seismic database in the IAEA External Events Safety Section (EESS) Portal b) Assessment of possibilities to use wave propagation based methods together with finite element analysis in seismic response analysis of SSCs c) MECOS expert group for looking the standard provisions for fatigue ratcheting in the case of seismic events d) Assessment on seismic behavior of aging pipe supports Organisation for Economic Co-operation and Development 17

18 RECENT REFERENCES OF WGIAGE NEA/CSNI/R(2017)11 Result of the benchmark on the analytical evaluation of the fracture mechanic parameters K and J for different components and loads NEA/CSNI/R(2017)2 Proceedings of the Fourth International Conference on Fatigue of Nuclear Reactor Components 28th September-1 October 2015 in Seville, Spain NEA/CSNI/R(2016)13 Final Report of Assessment of Structures subjected to Concrete pathologies (ASCET) phase 1 NEA/CSNI/R(2016)12 NEA/CSNI/R(2016)11 NEA/CSNI/R(2015)15 NEA/CSNI/R(2015)13 NEA/CSNI/R(2015)10 NEA/CSNI/R(2015)8 NEA/CSNI/R(2015)5 NEA/CSNI/R(2014)5 Probabilistic Structural Integrity of a Pressurised Water Reactor (PWR) Pressure Vessel - Final Report Results of questionnaire on Buried and Underground Tanks and Piping CSNI Workshop on Testing PSHA Results and Benefit of Bayesian Techniques for Seismic Hazard Assessment Pavia, Italy 4-6 February 2015 Questionnaire on Long-Term Operation of Commercial Nuclear Power Plants OECD NEA CSNI WGIAGE TASK ON HIGH ENERGY ARCING FAULT EVENTS (HEAF) Interim Report on Metallic Component Margins Under High Seismic Loads Bonded or Unbonded Technologies for Nuclear Reactor Prestressed Concrete Containments Improving Robustness Assessment Methodologies for Structures Impacted by Missiles (IRIS_2012) Final Report Organisation for Economic Co-operation and Development 18

19 Thank you for your attention All NEA publications and institutional documentation available at Organisation for Economic Co-operation and Development 19