ODIN - Small Punch Tensile/Fracture Test Datasets on Grade 91 steel from cryogenic to room temperature

Data collection containing small punch tensile/fracture data for tests on Grade 91 ferritic/martensitic steel performed between cryogenic and room temperatures. The material has the same chemical composition as P91/ T91 but is supplied in form of a plate rather than as pipe (P91) or tube (T91). The particular batch of Gr. 91 used in the present work (S50460) as part of the FP7 project MATTER was originally produced for the FP6 project EUROTRANS (project domain 4: DEMETRA). Disc-shaped small punch (SP) specimens as specified in the European Code of Practice were used. Their diameter was 8 mm and their thickness 0.5 mm. The surface roughness was less than Ra = 0.15 um on both sides. SP tensile/fracture mechanics tests were performed with varying displacement rates and temperatures as listed in Table 1. On the specimens tested at 0.5 mm/s X-ray computed tomography analysis has been carried out and the 3D surface has been reconstructed.JRC.F.4-Innovative Technologies for Nuclear Reactor Safet

INCEFA-PLUS (Increasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment)

INCEFA-PLUS is a European Project (funded by the European Commission HORIZON2020 program) that started in July 2015 and lasts five years (until June 2020). The project consists of 16 members from all over Europe and has as its main goal to guarantee safety in operations of Nuclear Power Plants (NPPs) by delivering experimental data to support the development of improved environmental fatigue assessment guidelines. The issues that are being studied (experimentally) are those of common interests to all participants: the effects of mean strain/stress, hold time, strain amplitude and surface finish on the fatigue performance of austenitic stainless steels in the LWR (Light Water Reactor) environment. Within the framework of the CEN (European Committee for Standardization) workshop FATEDA, the consortium developed a fatigue data format. This data format was used in an online environmental fatigue database, where the experimental data are made available for all participants. Later in the project, it is intended to develop an environmental fatigue assessment procedure on the basis of this data. The paper will introduce the project and describe phase one (of three) testing, including conditions such as surface finish and hold time. The plans that are being made for phase two testing will be detailed. The materials used in the tests, the surface finish data and some experimental results for phase one will be presented, together with a summary of the INCEFA-PLUS testing protocol. Finally, a review of existing assessment methodologies and a summary of dissemination activities will be provided.This project has received funding from the Euratom research and training program 2014-2018 under grant agreement No 66232

Test methodologies for determining high temperature material properties of thin walled tubes

This report presents briefly the test methods used, within the in the EERA JPNM Pilot Project TASTE, for defining the tensile and creep material properties relevant to the integrity of nuclear fuel claddings. These properties are challenging to extract from thin walled tubes since the standard test methods use test specimen that require minimum material thicknesses in the order of 10 mm or more. In consequence the thin walled material properties are acquired through a number of testing techniques and evaluation methodologies suitable for the thin walled product form. In this report the different test methods and their data assessment requirements are briefly described. The test methods evaluated here comprises of sub-size (curved specimen) tensile testing (ST) of the cladding tube, micro specimen (dog-bone) tensile testing (MT), Small Punch testing (SP), Segmented Expanding Cone Mandrel tests (SCM), the ring tension (RT) and ring compression (RC) tests and internal pressure testing (IP).JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

INCEFA-PLUS Findings on Environmental Fatigue

INCEFA-PLUS is a five year project supported by the European Commission HORIZON2020 programme. The project concluded in October 2020. 16 organisations from across Europe have combined forces to deliver new experimental data which is being used to develop improved guidelines for assessment of environmental fatigue damage to ensure safe operation of nuclear power plants. Within INCEFA-PLUS, the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue endurance of austenitic stainless steels in light water reactor environments have been studied experimentally. This document constitutes a Reference Book compiling the research developed within the INCEFA-PLUS Project. It provides a comprehensive overview of the tasks performed, and it also presents the background and the assumptions taken to develop the INCEFA-PLUS experimental and analytical works. It compiles and orders documents and contributions from INCEFA-PLUS partners.This project has received funding from the Euratom research and training program 2014-2018 under grant agreement No 662320

Creep strength and minimum strain rate estimation from Small Punch Creep tests

A new standard is currently being developed under the auspices of ECISS/TC 101 WG1 for the small punch testing technique for the estimation of both tensile and creep properties. Annex G of the new standard is covering the assessment and evaluation of small punch creep (SPC) data. The main challenge for estimating uniaxial creep properties from SPC data is the force to equivalent stress conversion between SPC and uniaxial creep tests. In this work a range of SPC assessment methodologies, benchmarked for the standard, are compared for verifying the best practice used in the standard. The estimated equivalent stresses for SPC are compared to uniaxial creep stresses at equal rupture times, using three alternative models. In-depth analyses are performed on SPC and uniaxial creep data for P92, F92 and 316 L steel tested within an inter-laboratory round robin. The formulation for SPC equivalent creep strain rate in the standard is also assessed

Characterization of Austenitic Stainless Steels with Regard to Environmentally Assisted Fatigue in Simulated Light Water Reactor Conditions

A substantial amount of research effort has been applied to the field of environmentally assisted fatigue (EAF) due to the requirement to account for the EAF behaviour of metals for existing and new build nuclear power plants. We present the results of the European project INcreasing Safety in NPPs by Covering Gaps in Environmental Fatigue Assessment (INCEFA-PLUS), during which the sensitivities of strain range, environment, surface roughness, mean strain and hold times, as well as their interactions on the fatigue life of austenitic steels has been characterized. The project included a test campaign, during which more than 250 fatigue tests were performed. The tests did not reveal a significant effect of mean strain or hold time on fatigue life. An empirical model describing the fatigue life as a function of strain rate, environment and surface roughness is developed. There is evidence for statistically significant interaction effects between surface roughness and the environment, as well as between surface roughness and strain range. However, their impact on fatigue life is so small that they are not practically relevant and can in most cases be neglected. Reducing the environmental impact on fatigue life by modifying the temperature or strain rate leads to an increase of the fatigue life in agreement with predictions based on NUREG/CR-6909. A limited sub-programme on the sensitivity of hold times at elevated temperature at zero force conditions and at elevated temperature did not show the beneficial effect on fatigue life found in another study

Aufbau und Erprobung eines repetierenden Laser-Blow-Systems zur Untersuchung elektrostatischer Elektronendichtefluktuationen in der Rand- und Abschälschicht

High anomalous transport is one of the key problems an the way to a burning plasma. Today it is generally assumed that this anomalous transport is caused by correlated fluctuations of the electric and magnetic fields, as well as of the particle densities and temperatures. The exact mechanisms are not yet, however, completely understood. Hence, the investigation of fluctuations currently has a high priority in fusion research. Therefore, the aim of this work was to determine to which extent Li-beams that are produced by means of laser blow-off (LBO) can be used for the investigation of fluctuations of the electron density in the edge and scrape-off layer of fusion devices and to carry out fluctuation measurements. For this purpose the LBO-system installed an the TEXTOR tokamak has been upgraded for repetitive operation and used for fluctation measurements an TEXTOR and an the Wendelstein 7-AS stellarator. The principle of this diagnostic is based an the excitation of Li atoms by collisions with electrons of the plasma and the following relaxation into the ground state. This transition into the ground state is accompanied by photon emission. For the total beam, the line emission is proportional the density of both, the Li atoms and the electrons. The penetration depth of the beam is limited by the increasing ionisation of the injected atoms caused by the rise of the electron density towards the plasma center. The spatial resolution in the direction of propagation of atomic beam diagnostics is determined by the velocity of the atoms and the relaxation time of the atomic processes involved. In the case of Li-LBO the spatial resolution is about 2 mm, which is ideal for the investigation of the spatial structure of electron density fluctuations, as these have a characteristic length of 5-15 mm in radial as well as in poloidal direction. Problems arise from the short length of the LBO pulses (ca. 100 p$\mu$) and the strong temporal variation of the Li flux, that has to be taken into account during the data evaluation. Numerical simulations Show that the radial velocity and correlation length of fluctuations of the electron density can be determined by Li-LBO. The use of this diagnostic for the investigation of the temporal behaviour and frequency spectrum is, however, rather restricted. On the basis of TEXTOR discharges it could be shown for the first time that this diagnostic can indeed be used for the investigation of fluctuations of the electron density in fusion devices. However, if the temporal variation of the Li flux is too pronounced an time scales that are short compared to the duration of the LBO pulses, the distinction between correlations that arise from plasma fluctuations and those that arise from variations of the Li flux can be difficult or even impossible. On Wendelstein 7-AS, this method has been shown to be a useful tool for the investigation of fluctuations. There, it was used in combination with other diagnostics to get new information an the structure of the fluctuation cells. In some discharges, a strong distinction between fluctuations in the core plasma and in the scrape-off layer could be seen. In the latter, the measured radial velocity is observed to drop with rising density. On the basis of discharges with different orientation of the magnetic field interpretations of the observed radial velocity are discussed

Environmental Fatigue Assessment of Metallic Materials and Components

At present, sensitive industrial sectors (such as the nuclear, oil, and gas sectors) face important challenges [...

ODIN Small punch test data for Gr. 91 steel

In the framework of its institutional project on Gen IV nuclear reactors, the JRC-IET performs pre-normative materials qualification research within the work package PreMaQ. The activities focus on evaluation methods like ultrasonic fatigue, neutron diffraction, thermoelectric power measurements, x-ray tomography, small punch creep and fracture tests, and nano-indentation with the aim to establish or prepare international standards. The current data set belongs to a small punch tensile/fracture mechanics test on the ferritic/martensitic steel Grade 91.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

Small punch tensile testing of curved specimens: Finite element analysis and experiment

The Small Punch (SP) technique is a miniature test used for characterizing irradiated materials or when a testing material is available only in small quantities. In this work Finite Element (FE) models are developed to support the parametric analysis of SP fuel cladding tube specimens in comparison to standard ones. FE analysis shows that there are practically no differences between circular and rectangular flat specimens. The tube specimen results in only slightly higher maximal force (Fm). However, Fm is attained at significantly lower displacements. This is attributed to the curvature of the specimen. The friction linearly increases the Fm and to a lesser extent displacement at Fm. FE analysis also shows that the yield stress and the hardening practically do not affect the Fm. Significant specimen deformation can be expected at already small (0.1 mm) puncher deflection, which could limit the applicability of the small punch test to ductile materials. Varying degree of clamping in the experimental procedure can cause large scatter in the yield stress estimates. In all cases good agreement between the simulation and experimental results was obtained, best with a friction coefficient of 0.2.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes