HVDC Submarine Power Cables in the World: State-of-the-Art Knowledge

This report is the first deliverable of the OTG ("Offshore Transnational Grid") Work Package (2015-2016), which is intended to identify and analyse the engineering and geopolitical challenges for realising a transcontinental energy interconnection between Europe and North America. The paper first of all addresses the principles of a High Voltage Direct Current (HVDC) power transmission system. Special attention is given to submarine cable interconnections. The spatial context of these cables is discussed. The used technologies and materials are addressed as well as the methods used to install and operate the cables. Additional aspects, such as safety and environmental issues, are also discussed. Further the report gives an overview of operational and planned HVDC submarine power cable systems. An extensive inventory list of these cables is annexed. Finally a set of conclusions are put forward, primarily pointing at further actions of the Work Package.JRC.F.3-Energy Security, Systems and Marke

A China-EU electricity transmission link: Assessment of potential connecting countries and routes

The report looks at the potential routes for a future power interconnection between EU and China. High voltage direct current technology is considered and its potential is assessed. It analyses the renewable energy sources in the countries along the potential routes as well as the power sector and power grid in the countries crossed. Three potential routes are analysed.JRC.C.3-Energy Security, Distribution and Market

Fracture Properties of Ductile Cast Iron Used for Thick-Walled Components

The report presents the outcome of a comprehensive programme of fracture experiments addressing three nuclear waste canister inserts, which have been produced from ductile cast iron. Specific aspects related to testing the ductile cast iron are considered. J-integral at fracture initiation and subsequent crack growth resistance are given for various sampling positions within the inserts and for two temperatures, i.e. 0ºC and room temperature. Basic statistical treatment of the data is performed and the results are related to other material properties.JRC.F.4-Nuclear design safet

Optimal Paths for Electricity Interconnections between Central Asia and Europe

The European Union is increasingly considering energy cooperation with Central Asia as this is a relatively nearby and stable region with tremendous energy resources. Locally produced electricity – i.e. predominantly from gas and hydro and potentially from solar and wind energy – offer opportunities for beneficial electricity trade, both among the Central Asian countries and with the European Union. As such, Central Asia may contribute to the European Union’s security of electricity supply and the achievement of its renewable energy targets. Underpinning policies and strategies for improved energy connectivity with Central Asia and the use of renewable energy sources in this region have been developed. However, efficient electricity interconnections are still lacking, hindering the full potential of Central Asia’s energy resources. Against this background, this report presents a methodology for the computation of optimal electricity transmission routes, crossing Central Asia, the Caspian Sea and the Transcaucasia towards the European Union. This methodology, which is based on the concept of friction maps, makes use of a set of 13 input variables and is implemented in geographic information system software. For each pixel of the friction map, covering the addressed countries, a crossing cost is calculated from semi-quantitative friction scores, which are locally attributed to the variables. Starting from the final cost surface, which represents a composite weighted map of the constituent variables, the software model successfully evaluates the least-cost paths for electricity transmission throughout the considered region. It is found that the evaluated route is most sensitive to the renewable energy potential across the considered region and not to the already existing electricity assets.JRC.C.3-Energy Security, Distribution and Market

Fracture Tests to Study the Behaviour of Simulated Sub-Surface Flaws in a Reactor Pressure Vessel Steel - a Continuation of the NESC-IV project

The NESC-IV project (2000 - 2005) addressed the transferability of fracture toughness data from laboratory specimens to applications that assess the integrity of reactor pressure vessels. This project included a series of uniaxial bend tests on large beams with a simulated shallow, sub-surface flaw. The results of these experiments pointed towards a significant constraint-loss effect in the ductile-to-brittle transition temperature range of the used steel, but in view of the inherent scatter in fracture toughness of low alloy steels in the given regime, further testing was recommended. Therefore the scope of present project was to perform a set of six additional tests with nominally identical test piece geometry, material and loading arrangements, so as to obtain a statistically more relevant data set. The Institute for Energy contracted the Nuclear Research Institute in Rez to perform these experiments. Following the successful execution of the tests, a preliminary fracture mechanics analysis was made to compare estimates of the stress intensity values at failure with the material's Master Curve. The results confirmed the constraint-loss effect, which had been observed in the previous NESC-IV test series. Moreover it was found that some aspects needed further attention, such as detailed finite element modelling of the experimental arrangements and accurate characterization of the test material's fracture toughness. The latter should also consider material inhomogeneity issues.JRC.F.4-Safety of future nuclear reactor

Constraint-Based Master Curve Analysis of a Nuclear Reactor Pressure Vessel Steel

This report presents the outcome of four fracture test series, addressing the ductile-to-brittle toughness behaviour of a nuclear reactor pressure vessel steel. Each test series corresponds to a specific test specimen geometry, tensile or three-point-bend, with a given degree of crack-tip constraint. A brief overview is given of available constraint-based fracture mechanics methodologies in the ductile-to-brittle transition range, including both engineering and local approach procedures. The obtained experimental data are analysed by means of the Master Curve standard ASTM E1921. Variability of the resulting reference temperature, T0, is successfully confirmed by a selection of constraint-based methodologies.JRC.DG.F.4-Safety of future nuclear reactor

Benchmark Analyses for Fracture Mechanics Methods for Assessing Sub-Clad Flaws - NESC-VI Final Report

The sixth project of the Network for Evaluating Structural Integrity (NESC-VI) deals with the fracture mechanics analysis of a set of 3 tests on beam specimens with simulated sub-surface flaws, which were performed by NRI Re¿ plc for the PHARE project ¿WWER Cladded Reactor Pressure Vessel Integrity Evaluation (with Respect to PTS Events)¿. The objectives were as follows: ¿ to assess the capability to predict whether the cracks propagating into the cladding arrest or cause full fracture, and ¿ to assess the capability to predict the location of first initiation: near-surface or deep crack tip. The project was launched in December 2006 and completed in March 2009. It brought together a group of 10 organisations from NESC to perform comparative analyses of selected tests, based on a comprehensive datapack prepared by NRI. The investigations focussed almost exclusively on assessing the capability to predict the location of first initiation. The main results are as follows: ¿ Comparison of analyses performed by individual partners showed that the FE simulations produced consistent predictions of the observed force vs. load-line displacement (or crack mouth opening displacement) behaviour. However the differences in predicted crack tip stress intensity, KJ, as a function of applied loading were greater than those found in similar intercomparisons made as part of previous NESC projects. This underlines the importance of periodically performing such exercises. ¿ The influence of two modelling factors on KJ was clearly established: firstly for this type of specimen, for which the clad makes up almost 12% of the cross-section, the associated residual stresses have a significant effect in reducing KJ values and therefore need to be considered in "best-estimate" analysis. The second concerns the use of 2-D or 3-D models: in this case the 2D FE models underestimated KJ values and are considered non-conservative. ¿ For this combination of test specimen geometry and flaw, constraint loss is expected at the near-surface tip. A range of constraint parameters were evaluated (elastic T-stress, elastic-plastic T-stress and Q) to confirm this. However only in two cases these were used in quantitative analyses: constraint-modified FAD and KIeff, both using elastic T-stress. These indicate that fracture is likely to initiate at lower (deep) tip, which is consistent with the limited high-speed video camera evidence. In general more systematic application of 2- parameter approaches is needed. ¿ Both local approach models predicted initiation of cleavage fracture first from the lower crack front for medium and higher loads. Concerning the capability to predict whether the cracks propagating into the cladding arrest or cause full fracture, the two analyses performed indicate that when the load at first pop-in is low, crack arrest in the clad can be correctly predicted on the basis of the J-R curve, but that further work is needed to ensure the reliability of such approaches over the full load range.JRC.F.4-Safety of future nuclear reactor

NESC-IV Project: an Investigation of the Transferability of Master Curve Technology to Shallow Flaws in Reactor Pressure Vessel Applications - Final Report

The NESC-IV project addressed the transferability of fracture toughness data from laboratory specimens to applications that assess the integrity of reactor pressure vessels subjected to upset and normal loading transients. The main focus was six biaxial bend cruciform tests of surface-breaking semi-elliptic defects in a RPV longitudinal weld and four uniaxial tests on extended sub-clad defects in RPV plate material. The co-ordinated experimental/analytical program drew from major elements of the US Heavy Section Steel Technology Program. Extensive materials testing and fracture analyses were performed by 20 European organizations, co-ordinated by the Network for Evaluating Structural Components (NESC).JRC.F.4-Nuclear design safet

On Ductility Variation of Ductile Cast iron for Spent Nuclear Fuel Packages and its Correlation with Casting Defects and Material Microstructure

This paper describes a study to correlate the variation in ductility in ductile cast iron to casting defects and the cast iron's microstructure. A large set of tensile and fracture specimens taken from three inserts for the Swedish KBS-3 programme were tested. About half the tensile specimens were analysed by metallography and fractography to identify and size defects and microstructural variations. It was found that the elongation at fracture was reduced by casting defects in the form of magnesium-oxide films and to a lesser extent by the graphite properties. An elastic-plastic probabilistic fracture mechanics model that relates the variation in ductility to the size and shape of casting defects is presented. The agreement between computed and measured results is quite good.JRC.F.4-Nuclear design safet

Characterization of defects and graphite types in ductile cast iron by image processing and its relation to mechanical properties

The paper presents a fast and reliable image processing tool to characterize graphite nodules and casting defects in ductile cast iron (IAOGT – Image Analysis of Graphite Types). Relationship between ductility of ductile cast iron and size of casting defects and different characteristic nodule properties (graphite type, feret, nodularity and nodule count) are indicated by analysis of 33 tested tensile specimens. The casting defects andvariation in nodule properties interact in a complex way but casting defects in the form of oxide films contribute most to low ductility. Low nodularity and low nodule count and high feret of graphite type III, IV-V also reduce ductility.JRC.F.4-Nuclear design safet