Inspecta Technology AB

Stockholm, Sweden

Inspecta Technology AB

Stockholm, Sweden
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Agency: European Commission | Branch: FP7 | Program: CP-CSA | Phase: Fission-2013-2.1.1 | Award Amount: 10.28M | Year: 2013

Preparing NUGENIA for HORIZON 2020 The objective of the NUGENIA\ project is to support the NUGENIA Association in its role to coordinate and integrate European research on safety of the Gen II and III nuclear installations in order to better ensure their safe long term operation, integrating private and public efforts, and initiating international collaboration that will create added value in its activity fields. The project consists of two parts, the first part being a Coordination and Support Action and the second part a Collaborative Project. The aim of the first part, the Coordination and Support Action, is to establish an efficient, transparent and high quality management structure to carry out the planning and management of R&D including project calls, proposal evaluation, project follow-up dissemination and valorisation of R&D results in the area of safety of existing Gen II and future Gen III nuclear installations. The preparatory work will encompass governance, organizational, legal and financial work, as well as the establishment of annual work plans, with the aim to structure public-public and/or private-public joint programming enabling NUGENIA to develop into the integrator of the research in the respective field in Europe. The management structure will build on the existing organisation of the NUGENIA Association, currently grouping over 70 nuclear organisations from research and industry (utilities, vendors and small and medium enterprises) active in R&D. In the second part, the Collaborative project, one thematic call for research proposals will be organized among the technical areas of plant safety and risk assessment, severe accident prevention and management, core and reactor performance, integrity assessment of systems, structures and components, innovative Generation III design and harmonisation of procedures and methods. The call will take place one year after the start of the project. The call will implement the priorities recognised in the NUGENIA Roadmap, in line with the Sustainable Nuclear Energy Technology Platform (SNETP) and International Atomic Energy Agency (IAEA) strategies. The research call which is going to be organised within the project is open to all eligible organisations. The NUGENIA\ project will benefit from the experience of the NUGENIA Association member organisations on managing national research programmes and from the track record of the NUGENIA project portfolio.


Bolinder T.,Inspecta Technology AB | Faleskog J.,KTH Royal Institute of Technology
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2015

In this work, the significance of residual stresses on ductile fracture is investigated by a set of experiments that are analyzed by finite element simulations. The treatment of residual stresses as expressed in fracture assessment procedures such as R6 is believed to be very conservative for ductile materials, when fracture occurs at high primary loads. Earlier numerical studies have reinforced this belief. This is supported in the current study. Tests on notched 3PB specimens with and without residual stresses were conducted on two ferritic steels. The residual stresses were introduced by applying a compressive preload on notched specimens. The tests were designed to achieve crack initiation at load levels around the plastic limit load. The crack growth in the tests was measured by a compliance method and by color marking of the crack surface. The crack tip driving force J was evaluated numerically for specimens with and without residual stresses. The experimental results show that the residual stresses clearly contribute to J at low primary loads. However, this contribution diminishes as the primary loads increase. The experimental results were also compared with results evaluated using the R6 procedure. These comparisons revealed overly high conservatism in R6 for cases with residual stresses compared to the ones for cases without residual stresses where less conservatism was evident. © 2015 by ASME.


Bolinder T.,Inspecta Technology AB | Sattari-Far I.,Inspecta Technology AB | Faleskog J.,KTH Royal Institute of Technology
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2011

In this work the significance of residual stresses for ductile fracture was investigated. The treatment of residual stresses as expressed in fracture assessment procedures such as the R6 method is believed to be very conservative for ductile materials, when fracture occurs at high primary loads. Earlier numerical studies have reinforced this belief. Tests on notched 3PB specimens with and without residual stresses were conducted on two ferritic steels. The residual stresses were introduced by applying a compressive pre-load on notched specimens. The tests were designed to achieve crack initiation at load levels around the limit load. The crack growth in the tests was measured by a compliance method and by colour marking of the crack surface. The crack-tip driving force J was evaluated numerically for specimens with and without residual stresses. The experimental results show that the residual stresses clearly contribute to J at low primary loads. However, this contribution diminishes as the primary loads increase. The experimental results were also compared with results evaluated using the R6 procedure. These comparisons revealed an overly high conservativeness in R6 for cases with residual stresses compared to the conservativeness for cases without residual stresses. Copyright © 2011 by ASME.


Koissin V.,Catholic University of Leuven | Shipsha A.,Inspecta Technology AB | Skvortsov V.,Saint Petersburg State University
Journal of Sandwich Structures and Materials | Year: 2010

This article deals with experimental, theoretical, and FE characterization of the local buckling in foam-core sandwich beams. In the theoretical approach, this phenomena is considered in a periodic formulation (unbounded wrinkle wave); a nonlinear stress-strain response of the face material is accounted for. In the FE approach, nonlinearity of the core material is also modeled. Full-field strain measurement is employed in the tests showing that the commonly used edgewise compression set-up can cause premature waviness of the faces, and therefore, nonlinear local deformations in the core layer. © The Author(s) 2010.


Svensson T.,TS Ingenjorsstatistik | Hannes D.,Inspecta Technology AB | Johannesson P.,SP Technical Research Institute of Sweden | Dahlberg M.,Inspecta Technology AB | Anderson A.,SP Technical Research Institute of Sweden
Procedia Engineering | Year: 2015

Fatigue bending tests have been performed on welded pipes made from an austenitic stainless steel. Four types of loading were used: 1) constant amplitude, 2) a load expected at pressure vessel environment, 3) a Gaussian load, and 4) a specially constructed two-level block load. The twenty-eight test results are evaluated using three different models: 1) the classical Basquin equation neglecting the fatigue limit, 2) the ASME model with a fatigue limit, and 3) a model with continuously decreasing fatigue limit. No significant differences between the three models were found. Predictions based on constant amplitude results appear to be non-conservative. © 2015 The Authors. Published by Elsevier Ltd.


Bonnaud E.,Inspecta Technology AB | Gunnars J.,Inspecta Technology AB
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2014

When manufacturing cylindrical or conical structures from metal plates, residual stresses originate from both welding and bending. The sequence in which these fabrication steps are carried out is essential as it can radically change the final distribution of residual stresses. To study this effect, detailed welding and bending simulations have been performed on both axial and circumferential X-welds of a 316L stainless steel cylindrical vessel. Bending after welding is shown to reduce residual stresses markedly more than bending before welding and the benefit on critical crack size is illustrated by a Fracture Mechanics analysis. Copyright © 2014 by ASME.


Mullins J.,Inspecta Technology AB | Gunnars J.,Inspecta Technology AB
Materials Science Forum | Year: 2011

Residual stresses predicted from welding simulations are known to be sensitive to the choice of material model. Recent work has shown large differences in the predicted residual stress profile when different types of hardening model are used (isotropic, kinematic or mixed models). More information is required regarding the exact deformation conditions that exist during welding. We consider finite element models of two multi-pass, stainless steel girth welds. Temperature, stress and plastic strain histories are recorded in the weld material and in the heat affected region (HAZ). Material in the weld and HAZ is observed to undergo three to five cycles of active plastic deformation followed by thermal cycling that is purely elastic. The stress state varies from biaxial compression to triaxial tension. These deformation histories are used as the basis for a discussion of the formulation of a suitable material testing schedule and subsequent constitutive modelling.


Cronvall O.,VTT Technical Research Center of Finland | Simola K.,VTT Technical Research Center of Finland | Mannisto I.,VTT Technical Research Center of Finland | Gunnars J.,Inspecta Technology AB | And 3 more authors.
Reliability Engineering and System Safety | Year: 2012

Leakages and ruptures of piping components lead to reduction or loss of the pressure retaining capability of the system, and thus contribute to the overall risk associated with nuclear power plants. In-service inspection (ISI) aims at verifying that defects are not present in components of the pressure boundary or, if defects are present, ensuring that these are detected before they affect the safe operation of the plant. Reliability estimates of piping are needed e.g., in probabilistic safety assessment (PSA) studies, risk-informed ISI (RI-ISI) applications, and other structural reliability assessments. Probabilistic fracture mechanics models can account for ISI reliability, but a quantitative estimate for the latter is needed. This is normally expressed in terms of probability of detection (POD) curves, which correlate the probability of detecting a flaw with flaw size. A detailed POD curve is often difficult (or practically impossible) to obtain. If sufficient risk reduction can be shown by using simplified (but reasonably conservative) POD estimates, more complex PODs are not needed. This paper summarises the results of a study on the effect of piping inspection reliability assumptions on failure probability using structural reliability models. The main interest was to investigate whether it is justifiable to use a simplified POD curve. Further, the study compared various structural reliability calculation approaches for a set of analysis cases. The results indicate that the use of a simplified POD could be justifiable in RI-ISI applications. © 2011 Elsevier Ltd. All rights reserved.


Bonnaud E.,Inspecta Technology AB | Gunnars J.,Inspecta Technology AB
Procedia Engineering | Year: 2015

Weld Residual Stresses are a major concern as they markedly reduce reliability. Accurate prediction is therefore essential and is usually carried out by mean of Finite Element Analysis. In many cases, two dimensional axisymmetric modelling is sufficient but comparison with measurement has shown limitations. Full 3D simulations are therefore now preferred in several applications and especially when it comes to studying start/stop and (partial) repair effects. These two events have here been simulated in 3D and comparison with 2D results indicate a significant increase in Weld Residual Stresses. As an illustration, the reduction on critical crack size is assessed by a Fracture Mechanics analysis. © 2015 The Authors.


Bremberg D.,Inspecta Technology AB | Gunnars J.,Inspecta Technology AB | Bonnaud E.,Inspecta Technology AB | Edling L.-O.,Forsmarks Kraftgrupp AB | Kingston E.,VEQTER Ltd.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2014

Internal components in nuclear reactor pressure vessels are joined to the ferritic vessel by use of dissimilar metal welds which commonly include nickel base weld material Alloy 182. It has turned out that Alloy 182 sometimes is susceptible to stress corrosion cracking (SCC) for the operating environment in reactors. Tensile residual stress has a large influence on SCC and it is important to carefully characterize the residual stresses generated at manufacturing. The manufacturing of these welds includes welding Alloy 182 to the ferritic steel to form a buttering, post-weld heat treatment (PWHT) of the buttering, and finally attachment welding between the internal component and the buttering. An experimental program was designed for measurement and numerical analysis for validation of residual stresses in a nickel base Alloy 182 weld between the core shroud support leg and reactor pressure vessel. Two full-scale mock-ups were manufactured according to the original procedures for the buttering to the ferritic steel and the final attachment weld to the core shroud support. The mock-up was also carefully designed to produce correct boundary conditions for the support leg. Measurements were performed by the deep-hole drilling technique (DHD/iDHD). The residual stress fields from welding and heat treatments were predicted by detailed numerical modelling. Comparison between the numerical results and the measurement results shows very good agreement and validates the predicted residual stresses. It was concluded that the PWHT of the vessel only partly relieve weld residual stresses in the nickel base buttering. Copyright © 2014 by ASME.

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