Environmental Fatigue Analysis of nuclear components within the framework of INCEFA-SCALE project

ABSTRACT: INCEFA-SCALE started in October 2020. The objective of this project is to improve the capacity to predict the lifetime of Nuclear Power Plant (NPP) components subjected to environmental assisted fatigue. The project starts off by analysing the existing data and then provides new environmentally assisted fatigue data which allow the laboratory test outcomes to be applied to components with real geometries and loads. So far, the data mining of different finished projects (INCEFA-PLUS, USNRC, EPRI, MHI and AdFaM) has been carried out, and test conditions for filling the knowledge gaps have been established. Moreover, the test matrix for 2022 has been defined. In this first phase, tests are focused on producing reference data, analysing complex waveforms (variable amplitude) and the effect of the surface finish. The next testing phases will focus on particular conditions: multi-axial tests, notches, stress/strain gradient effect and size effect. Furthermore, the microstructural analysis of common materials and a guideline for fatigue striation measurement on the fracture surface have been developed. This article provides an update on the project status and the advances made in data analysis, mechanical understanding and testing conditionsThis project has received funding from the Euratom research and training program 2019-2020 under grant agreement No 945300. The contributions of all partners in the INCEFA-SCALE project are also acknowledge

PTPA variants and impaired PP2A activity in early-onset parkinsonism with intellectual disability

The protein phosphatase 2A complex (PP2A), the major Ser/Thr phosphatase in the brain, is involved in a number of signalling pathways and functions, including the regulation of crucial proteins for neurodegeneration, such as alpha-synuclein, tau and LRRK2. Here, we report the identification of variants in the PTPA/PPP2R4 gene, encoding a major PP2A activator, in two families with early-onset parkinsonism and intellectual disability. We carried out clinical studies and genetic analyses, including genome-wide linkage analysis, whole-exome sequencing, and Sanger sequencing of candidate variants. We next performed functional studies on the disease-associated variants in cultured cells and knock-down of ptpa in Drosophila melanogaster. We first identified a homozygous PTPA variant, c.893T&gt;G (p.Met298Arg), in patients from a South African family with early-onset parkinsonism and intellectual disability. Screening of a large series of additional families yielded a second homozygous variant, c.512C&gt;A (p.Ala171Asp), in a Libyan family with a similar phenotype. Both variants co-segregate with disease in the respective families. The affected subjects display juvenile-onset parkinsonism and intellectual disability. The motor symptoms were responsive to treatment with levodopa and deep brain stimulation of the subthalamic nucleus. In overexpression studies, both the PTPA p.Ala171Asp and p.Met298Arg variants were associated with decreased PTPA RNA stability and decreased PTPA protein levels; the p.Ala171Asp variant additionally displayed decreased PTPA protein stability. Crucially, expression of both variants was associated with decreased PP2A complex levels and impaired PP2A phosphatase activation. PTPA orthologue knock-down in Drosophila neurons induced a significant impairment of locomotion in the climbing test. This defect was age-dependent and fully reversed by L-DOPA treatment. We conclude that bi-allelic missense PTPA variants associated with impaired activation of the PP2A phosphatase cause autosomal recessive early-onset parkinsonism with intellectual disability. Our findings might also provide new insights for understanding the role of the PP2A complex in the pathogenesis of more common forms of neurodegeneration.</p

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A scaling approach to model history effects in fatigue crack growth under mixed mode I+II+III loading conditions for a 316L stainless steel

International audienc

Peridynamic numerical investigation of asymmetric strain-controlled fatigue behaviour using the kinetic theory of fracture

Abstract Numerical fatigue process modelling is complex and still an open task. Discontinuity caused by fatigue cracks requires special finite element techniques based on additional parameters, the selection of which has a strong effect on the simulation results. Moreover, the calculation of fatigue life according to empirical material coefficients (e.g., Paris law) does not explain the process, and coefficients should be set from experimental testing, which is not always possible. A new nonlocal continuum mechanics formulation without spatial derivative of coordinates, namely, peridynamics (PD), which was created 20 y ago, provides new opportunities for modelling discontinuities, such as fatigue cracks. The fatigue process can be better described by using the atomistic approach-based kinetic theory of fracture (KTF), which includes the process temperature, maximum and minimum stresses, and loading frequency in its differential fatigue damage equation. Standard 316L stainless steel specimens are tested, and then the KTF-PD fatigue simulation is run in this study. In-house MATLAB code, calibrated from the material S‒N curve, is used for the KTF-PD simulation. A novel KTF equation based on the cycle stress‒strain hysteresis loop is proposed and applied to predict fatigue life. The simulation results are compared with the experimental results, and good agreement is observed for both symmetric and asymmetric cyclic loading

Residual Stress and Shrinkage Predictions on 14" Narrow Gap Dissimilar Metal Welds

For nuclear reactor applications, AREVA NP has to perform junctions between ferritic low alloy steel heavy section components and austenitic stainless steel piping systems. In these cases, welding remains the key process and AREVA NP has developed, for this kind of Dissimilar Metal Welds (DMW), narrow gap techniques requiring special manufacturing procedures to ensure a good resistance of the junctions. In parallel, numerical welding simulation has already proved its relevance to predict residual stress fields in welded components and becomes more and more a real support for industrial design engineers. This paper presents computations performed by AREVA NP on several 14" narrow gap DMW configurations. The simulations focused on the predictions of residual stress fields, for integrity issues, and shrinkages for manufacturing ones. Considering 2D axisymmetric hypotheses, the analyses simulate each elementary step of the mock-up manufacturing procedures. Multipass welding simulations reproduce the deposit of each bead by thermo-metallurgical and mechanical calculations. Note that non linear kinematic hardening models, strain annealing and phase transformation techniques, and self-clamping boundary conditions are used. The numerical results are in a good agreement with experimental data provided by neutron diffraction measurements and welding recording data. Thus, this work enables to give another evidence of the relevance of the numerical welding simulation and highlights the capability for AREVA NP to perform, with success, such a kind of analyses.JRC.DDG.F.4-Safety of future nuclear reactor

Numerical Welding Simulation on a 14'' Narrow Gap Dissimilar Metal Weld

AREVA NP has developed narrow gap weld techniques to perform junctions between ferritic low alloy steel heavy section components and austenitic stainless steel piping systems. In parallel, numerical welding simulation has already demonstrated its relevance to predict residual stress fields in welded components. This paper presents computations on a 14" narrow gap Dissimilar Metal Weld (DMW) configuration. The analysis simulates each elementary step of the mock-up manufacturing procedure. Multipass welding simulation reproduces the deposit of each bead by thermo-metallurgical and mechanical calculations. The main original points of the work are: ¿ The choice of non linear kinematic hardening models, ¿ The use of strain annealing and phase transformation techniques, ¿ The post weld heat treatment simulation. For validation, the numerical results are compared to measurements obtained by both neutron diffraction and deep hole drilling techniques. The residual stress fields are observed at various locations from the weld centreline, in the depth of the pipe, and a very good agreement is obtained. Within the framework of narrow gap DMW configurations, this work gives another evidence of the relevance of the numerical welding simulation and highlights the capability for AREVA NP to perform, with success, such a kind of analyses.JRC.F.4-Safety of future nuclear reactor

Load path effect on fatigue crack propagation in I+II+III mixed mode conditions – Part 2: Finite element analyses

International audienc

INCEFA-SCALE (Increasing Safety in NPPs by Covering Gaps in Environmental Fatigue Assessment - Focusing on Gaps Between Laboratory Data and Component-Scale)

INCEFA-SCALE is a five-year project supported by the European Commission HORIZON2020 programme. It is the successor to the INCEFA-PLUS programme that ran from 2015 to 2020. INCEFA-SCALE kicked off in September 2020. The objective is to continue work, advancing the ability to predict lifetimes of Nuclear Plant components when subjected to Environmental Assisted Fatigue loading (EAF). It has been generally observed by nuclear plant operators that there appears to be a disconnect between the perceived difficulty of providing an acceptable assessment result with the current EAF methodologies and the good service experience with regard to this specific degradation mechanism. It is internationally recognised that a possible contributor to this discrepancy is the transferability of laboratory-scale tests to real nuclear components. EPRI, in the USA, is leading a series of component-scale environmental fatigue tests that are expected to advance data availability significantly; however, the ability to address transferability of laboratory-scale tests to real component geometries and loadings will still be constrained by limited test data. This is the knowledge gap addressed by INCEFA-SCALE. The project strategy will be (1) the development of comprehensive mechanistic understanding developed through detailed examination of test specimens and MatDB datamining, and (2) testing focussed on particular aspects of component-scale cyclic loading.INCEFA-PLUS project, and from other external sources such as USNRC, EPRI, MHI and the AdFaM project). In parallel, the test programme needs have been agreed, and protocols agreed for managing data, testing, and material examinations consistently. Testing commenced after one year and will run for three years. Finally, the project will deliver guidance on the use of laboratory-scale data for component-scale applications. This paper will report the first year of the project and detail the preparations completed to ensure the project maximises the achievement of its objectives.</p