International Workshop: Materials resistant to extreme conditions for future energy systems: Book of Abstracts

This is the third Workshop on Physics-Based Models and Experimental Validation funded by the European Union's Enlargement and Integration Programme with creep and plastic deformation of metals as the focus theme this year. In addition to provide a platform for collaboration and exchange of information between researchers in EU Member States and the target countries, the Workshop also aims to bring together students and international experts, scientists addressing more basic research with code developers and industrial end-users and to provide cross-cutting by involving scientists from different sectors such as nuclear, aerospace and automotive. Material is the key for the development of our future society such as new energy system, transport system and electronic equipment. The material properties, performance of components in different environments and associated material degradation mechanism depend on the microstructure and chemical composition of the material. By "physics-based" we refer to models that address microstructures and associated thermodynamic non-equilibrium mechanisms and processes at different length and time scales. Such models include molecular dynamics, dislocation dynamics and crystal plasticity. The basic foundation for such models were established in the 20th century but the further development and application to industrial problems is of more recent date thanks to the dramatic improvement of computational power. The ultimate goal is to combine several models, including continuum based phenomenological models, into a multi-scale approach to address complex material properties and also application to industrial components. Although one of the drivers for physics-based models is to replace the need for expensive material testing, experiments will be needed to develop, calibrate and validate physics-based and multi-scale models. Thus the integration of physics-based models and innovative experimental techniques are clearly coupled. The physics based models can be used for design of new materials with tailored properties or reducing the cost and time for development of new materials using physics-based models integrated with experiments. This research is therefore singled out as a key priority in broader research programmes. The Workshop consists of ten keynote lectures, 19 oral presentations and a Poster session with over 50 posters. New developments and applications of the various physics-based models as well as some cases for scale bridging will be presented. There are also presentations on specific experimental techniques and on some that address the applicability for industrial applications.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

On Plastic Collapse Analysis of KBS-3 Canister Mock-Up

This report describes an in-depth finite element simulation of a spent fuel canister for geological disposal loaded in iso-static pressure until plastic collapse. The canister consists of a copper overpack and a ductile cast iron insert with steel cassettes where the spent fuel is placed. The higgly non-linear finite element analysis is based on the explicit formulation and includes large deformations, non-linear material behaviour and contact between the canister components. The analysis includes comparison between two-and three dimensional models and assessment of the different geometrical features such as corner radius of the cassette, cassette off-set, different bonding/dedonding conditions between insert and steel cassette. The analysis shows that the bonding cassette/insert has a large impact on the collapse load. Two large-scale mock-ups test that had been performed earlier are also simulated by the developed finite element models. There is a very good agreement between measured and computed deformations versus applied load and collapse load.JRC.F.4-Nuclear design safet

A Prospective Study for Probabilistic Approach of Thermal Fatigue in Mixing Tees

The work performs a prospective study on probabilistic approach of thermal fatigue in mixing tees (Civaux 1 damage case) by means of the limit state function and Monte Carlo simulation. It is based on previous work where a deterministic assessment for thermal fatigue crack growth in high-cycle loadings, under the large nonlinear gradient stress profiles through wall-thickness due to sinusoidal thermal loading, has been done.The probabilistic approach considers variability in initial crack depth and Paris law C scaling parameter by means of specific probability density distributions. The crude Monte Carlo Simulations are performed using specific routines implemented in MATLAB software with Statistics Toolbox, and probabilities of failure are derived using the failure function which is defined based on a limit state given by the critical crack depth. The results were checked against predictions from empirical cumulative distribution and a good agreement was found. An important task was to estimate distribution function for fatigue lives after finding probabilities failure associated with corresponding fatigue lives by means of the failure function approach. Using specific MATLAB functions from Statistic Toolbox, for both axial and circumferential crack growth the pdf, associated mean value of the fatigue life and CoV have been estimated. The log-normal distribution has been found to best fit the results from failure function approach with MCS, for both cases.JRC.F.4-Safety of future nuclear reactor

Assessment of Thermal Fatigue Crack Growth in the High Cycle Domain under Sinusoidal Thermal Loading - An Application - Civaux 1 Case

The assessment of fatigue crack growth due to cyclic thermal loads arising from turbulent mixing presents significant challenges, principally due to the difficulty of establishing the actual loading spectrum. So-called sinusoidal methods represents a simplified approach in which the entire spectrum is replaced by a sine-wave variation of the temperature at the inner pipe surface. The amplitude can be conservatively estimated from the nominal temperature difference between the two flows which are mixing; however a critical frequency value must be determined numerically so as to achieve a minimum predicted life. The need for multiple calculations in this process has lead to the development of analytical solutions for thermal stresses in a pipe subject to sinusoidal thermal loading, described in a companion report. Based on these stress distributions solutions, the present report presents a methodology for assessment of thermal fatigue crack growth life. The critical sine wave frequency is calculated for both axial and hoop stress components as the value that produces the maximum tensile stress component at the inner surface. Using these through-wall stress distributions, the corresponding stress intensity factors for a long axial crack and a fully circumferential crack are calculated for a range of crack depths using handbook K solutions. By substituting these in a Paris law and integrating, a conservative estimate of thermal fatigue crack growth life is obtained. The application of the method is described for the pipe geometry and loadings conditions reported for the Civaux 1 case. Additionally, finite element analyses were used to check the thermal stress profiles and the stress intensity factors derived from the analytical model. The resulting predictions of crack growth life are comparable with those reported in the literature from more detailed analyses and are lower bound, as would be expected given the conservative assumptions made in the model.JRC.F.4-Nuclear design safet

2nd International Workshop on Physics-Based Modelling of Material Properties and Experimental Observations with special focus on Fracture and Damage Mechanics: Book of Abstracts

This report covers the book of abstracts of the 2nd International Workshop on Physics Based Modelling of Material Properties and Experimental Observations, with special focus on Fracture and Damage Mechanics. The workshop is organized in the context of European Commission’s Enlargement and Integration Action, by the Joint Research Centre in collaboration with the TOBB University of Economics and Technology (TOBB ETU) on 15th-17th May 2013 in Antalya, Turkey. The abstracts of the keynote lectures and all the technical presentations are included in the book. This workshop will give an overview of different physics-based models for fracture and degradation of metallic materials and how they can be used for improved understanding and more reliable predictions. Models of interest include cohesive zones to simulate fracture processes, ductile-brittle transition for ferritic steels, ductile fracture mechanisms such as void growth or localized shear, fatigue crack initiation and short crack growth, environmental assisted cracking. Experimental studies that support such models and case studies that illustrate their use are also within the scope. The workshop is also an opportunity for scientists and engineers from EU Member States and target countries to discuss research activities that could be a basis for future collaborations.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

PVP2008-61853 THERMAL FATIGUE CYCLIC-DOWN SHOCKS ON 316L MODEL PIPE COMPONENTS

ABSTRACT There is a continuing need for reliable thermal fatigue analysis tools to ensure that high safety levels are maintained in the main coolant lines of light water reactors. To advance the accuracy and reliability of thermal fatigue load determination, a combined experimental and numerical investigation has been conducted on cylindrical components of 316L stainless steel subjected to cyclic thermal shocks of varying intensity. Slightly different experimental conditions were applied in each test to explore the effect of ∆T max values of increasing severity, the effect of a superimposed static axial load and a reduced test piece wall thickness. Particular attention is given in this work to the influence of a constant tensile axial load on the quenching down shock damage. A comparison between thermal down-shock tests with and without additional constant tensile load is analysed in details here below

Development of the Mandrel Test for Controlled Displacement of Zircaloy Tubes : Summary of Initial Work 2007

This report describes some initial work at IE to develop a displacement controlled test for testing the material properties of spent fuel cladding tubes. The objective is to have a test which allows stavle failure under increasing and for which the level of axisymmtery can be controlled. The cone-Mandrel test consists of a set of arc-shaped segments placed inside a section of a Zircaloy tube and pushed outwards by the vertical displacement of a conical shaft. The cone-mandrel is first developed for un-irradiated conditions but the test should also be applicable for irradiated components in hot cells at ITU. The report describes the practical implementation of the cone-mandrel with 8 segments and applied to three specimens. The tests show that the cone-mandrel can be used to attain controlled displacements until failure. The load is not accurately monitored for very low loads due to misalignment between cone, segments and tube. It is, however, straight-forward to compensate for this effect from the registered displacement/strain curve. The tested specimens were subsequently analysed by fractographic studies. The main fracture was by shearing along lines that make 45¿ angle with the axial and circumferential directions. The tests were simulated by non-linear finite element (FE) calculations. The finite element calculations simulated the experimental observations quite well. The FE calculations also allowed us to better understand the failure by necking and the deviation of axi-symmetric loading due to stress concentrations at the end of the segments. Furthermore the cone is also subjected to plastic deformation. The plastic deformation of the cone and the deviation from axi-symmetric load conditions can be reduced by increasing the number of segments. To this end mandrels with 6, 8 and 10 segments were analysed. The conclusion is that one should use at least 8 segments and that one should use a harder material for the cone.JRC.F.4-Safety of future nuclear reactor

Creep Simulations of Nuclear Fuel Cladding under long term Storage Conditions with TRANSURANUS

Within a joint research project between the Institute for Energy (IE) and the Institute for Transuranium Elements (ITU) on the integrity of spent nuclear fuel cladding the ITU code TRANSURANUS was used to simulate creep of Zircaloy cladding tubes under long term storage conditions. Since TRANSURANUS is designed to model the mechanical, thermal and physical behaviour of fuel rods during reactor operation it was the objective of this study firstly to explore the limitations of the present creep models in TRANSURANUS for the simulation of long term creep processes under dry storage conditions. If the present creep models in TRANSURANUS were found to be inappropriate then the next objective was to formulate the properties of an "ideal" creep model for dry storage. The creep models were compared with creep tests on unirradiated Zircaloy cladding tubes. It turned out that the standard creep model for Zircaloy cladding in TRANSURANUS, the model of Lassmann and Moreno, underestimated the creep strains of the tests significantly. The creep model of Mayuzumi and Onchi, which was designed to model long term creep processes under dry storage conditions, lead to reasonable agreement with the creep tests for temperatures of 350 degrees Celcius and above. It turned out that for the accurate prediction under low-temperature conditions (under 350 degrees Celcius) more sophisticated creep models, which account for a shift in creep mechanisms, are necessary.JRC.F.5-Safety of present nuclear reactor

Microstructural analysis of thermal fatigue damage in 316L pipes

This report summarizes the data and main conclusions derived from microstructural characterisation of 316L pipes subjected to thermal fatigue with a peak temperature of 550°C. TOFD measurements are compared with measured crack depths from cut segments, and fracture mode and corrosion have been assessed by SEM and EDX, respectively.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Scientific Assessment in support of the Materials Roadmap enabling Low Carbon Energy Technologies: Technology Nuclear Energy

This scientific assessment serves as the basis for a materials research roadmap for the nuclear fission technology, itself an integral element of an overall "Materials Roadmap Enabling Low Carbon Technologies", a Commission Staff Working Document published in December 2011. The Materials Roadmap aims at contributing to strategic decisions on materials research funding at European and Member State levels and is aligned with the priorities of the Strategic Energy Technology Plan (SET-Plan). It is intended to serve as a guide for developing specific research and development activities in the field of materials for energy applications over the next 10 years. This report provides an in-depth analysis of the state-of-the-art and future challenges for energy technology-related materials and the needs for research activities to support the development of nuclear fission technology both for the 2020 and the 2050 market horizons. It has been produced by independent and renowned European materials scientists and energy technology experts, drawn from academia, research institutes and industry, under the coordination the SET-Plan Information System (SETIS), which is managed by the Joint Research Centre (JRC) of the European Commission. The contents were presented and discussed at a dedicated hearing in which a wide pool of stakeholders participated, including representatives of the relevant technology platforms, industry associations and the Joint Programmes of the European Energy Research Associations.JRC.F.4-Safety of future nuclear reactor