Stainless Steel Conduit Research Articles

Experimental Assessment of the Thermal Strain Distribution in Nb3Sn React & Wind Conductor Prototype for European DEMO

In a typical Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable for fusion applications, the knowledge of the strain state of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn filaments is important to predict and interpret the conductor performance in operation. Amongst the relevant strain sources, the predominant is the thermal strain that arises during the cool-down of the conductor to operating temperature, due to the different expansion of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn and copper in the cable and the stainless steel conduit. This work addresses the characterization of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn thermal strain in the React & Wind prototype (RW2) developed by EPFL-SPC for the toroidal field coil and the central solenoid of the EUROfusion DEMO fusion reactor. AC susceptibility measurements were performed on the RW2 prototype to assess the thermal strain distribution in the cable cross-section, before and after undergoing electromagnetic and thermal cyclic loading. The results of the analysis have shown that RW2 exhibits a significantly lower absolute mean strain value (about −0.3%), compared to many Wind & React ITER conductor samples investigated with the same method. In addition, the analysis highlighted that the assessed thermal strain distribution does not vary significantly before and after the electromagnetic and thermal cycles, confirming the small performance degradation in the RW2 conductor that has been recently reported.

Estudio experimental del rendimiento térmico de un colector solar de tubos evacuados para calentar aire de secado

A solar collector with evacuated tubes was developed to heat air from room temperature until it has the capacity to be used in drying processes. The instantaneous and global thermal efficiency of the equipment was studied, as well as the behavior of the outlet temperature at different air flows. Measurements of inlet and outlet air temperatures, irradiance were taken, and mass flow were determined. The amount of heat absorbed by the air was calculated and, in relation to the irradiance, instantaneous efficiency was obtained to later determine the overall efficiency. The device consists of a polypropylene tube where 5 evacuated tubes were placed. Air was flowed into each of them with an arrangement of a stainless-steel conduit with thin-walled tubing. For various air flows, thermal behavior curves were obtained, where increases in air temperature between 30°C and 50°C were observed, reaching outlet temperatures of up to 90°C. Efficiencies were calculated from 40% to 60%, for high and low operating temperatures, respectively. The increase in temperature resulted in a linear trend, facilitating the design of instrumented dryers and their control.

Overview of verification tests on AC loss, contact resistance and mechanical properties of ITER conductors with transverse loading up to 30 000 cycles

The ITER magnet system uses cable-in-conduit conductor (CICC) technology with individual strands twisted in several stages resulting in a rope-type cable, which is inserted into a stainless steel conduit. The combination of high current (up to 68 kA) and background magnetic field (up to 13 T) results in large transverse Lorentz forces exerted on the conductors during magnet system operation. The high transverse forces, accompanied with the cyclic nature of the load, have a strong influence on the conductor properties. The Twente Cryogenic Cable Press is used to simulate the effect of the Lorentz forces on a conductor comparable to the ITER magnet operating conditions. An overview is presented of the AC coupling and hysteresis loss, mechanical deformation characteristics and inter-strand contact resistance measurement results obtained on full-size ITER CICCs measured in the Twente Cryogenic Cable Press. The aim of this work is to characterize conductors’ electromagnetic and mechanical properties during cycling of the load up to 30 000 cycles. The evolution of the magnetization (AC coupling loss time constant nτ), mechanical properties and inter-strand resistance Rc between selected strands is presented along with loading history. The Rc between first triplet strands is also measured as a function of applied load. It is shown that transverse load cycling has a strong influence on the CICC properties. An overview of the results for eight toroidal field conductors, two central solenoid conductors, three poloidal field conductors of different types (PF1&6, PF4, PF5), one main bus-bar and one correction coil conductor is presented.

EFFECT OF AGING ON MECHANICAL PROPERTIES OF 316LN AT 4.2 K FOR FUSION APPLICATIONS

Within the fusion magnet technology the low-temperature superconductor Nb3Sn is usually used for high magnetic field in the range of 12 T and 4.5 K. These superconductors are produced as round strands. Here Nb3Sn filaments are embedded in a round copper matrix with a diameter of about 0.8 mm. To allow magnet windings of several Mega-Ampere to produce the needed magnetic field, about 900 superconducting strands are cabled and compacted in a stainless steel conduit resembling the so-called cable-in-conduit-conductor (CICC). However, the mechanically brittle Nb3Sn superconducting phase is produced by the diffusion reaction by a long-term heat treatment. Therefore, the magnet winding containing the superconducting strands together with the stainless steel jacket has to undergo this heat treatment. In order to simulate the magnet manufacturing process, seamless tubes were compacted, bend and straightened and tensile stretched by 2.5 % at room temperature followed by the heat treatment necessary for the Nb3Sn formation. The aim of this study was to compare the microstructures and tensile properties at cryogenic operation temperature of two modified 316LN austenitic stainless steels with very-low carbon (≤ 0.013) in the as built conditions and after heat treatments. Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD) and X-ray diffraction were used to study microstructure. Deformation behaviour was investigated by tensile test at 4.2 K.

Design and R&amp;D for the DEMO Toroidal Field Coils Based on Nb3Sn React and Wind Method

In 2013, the Swiss Plasma Center proposed a Toroidal Field (TF) layout for the DEMO-EUROfusion tokamak, based on a graded winding made of layers of Nb3 Sn (react&wind) and NbTi conductors. The R&D effort led in 2015 to a full size prototype conductor tested up to 82.4 kA at 12.35 T. The test continued in 2016 and new results are presented. In summer 2015 a new reference baseline was issued for the DEMO-EUROfusion tokamak, leading to an update of the TF requirements. The design update is presented in this paper, with the winding pack consisting of 12 single layers of Nb3 Sn with “invisible” (no protrusion) inter-layer joints. The high grade Nb3 Sn react&wind conductor operates at 63.3 kA, 12.23 T with T cs > 6.5 K. A new prototype conductor is being manufactured. The main advantages of the graded approach, applied to both the superconductor and the stainless steel conduit, are a substantial space and cost saving compared to the wind&react approach with pancake winding.

Study on the Fatigue Properties of the TIG Weld Joint with the Stainless Steel Conduit in Aircraft

The research focus on the material of the stainless steel thin conduit in aircraft, named 1Cr18Ni9Ti , and the TIG weld joint of which was investigated to analysis the fatigue properties. The fracture mechanics was used to analysis the crack initiation life and crack propagation life, and the fatigue surface was characterized with scanning electron microscope (SEM). The experimental and analytical results show that, the origin position of fatigue crack is the surface of the conduit. The stress concentration at the weld toe, the crystal structure is not uniform and Stress concentration in the heat affected zone (HAZ) and fusion line, so the fatigue cracks are easily generated in these locations. Delta K increases to a certain value, the HAZ has become one of the most dangerous position. The crack initiation life of HAZ in the total fatigue life is far higher than the proportion of crack propagation life.

Investigation of Frictional Force Applied to Strands Surrounded by Other Strands and Tribological Analysis of Contact Surface in CIC Conductor

At the SULTAN test facility, the assessment of the performance of toroidal field coils has been progressing. Unpredictable strand buckling was observed during the destructive investigation of the conductor after significant degradation of the current sharing temperature. The buckling direction was perpendicular to the Lorentz force (LF), and the mechanism causing this was due to the thermal shrinkage occurring because of the difference in the thermal contraction between the strand material and the stainless steel conduit. Our previous research was based on a two-dimensional string model and demonstrated that the observed 2 mm strand bending could have led to strand buckling if the total amount of slide at the contact crossover was assumed to be 80 μm. To verify this assumption, we fabricated a device for the measurement of the friction force (shear force) between strands under a constriction force comparable to the LF of several hundred of kilonewtons per meter. The results for a Cr-coated 0.89 mm diameter strand surrounded by bare Cu strands indicated that the thermal contraction force would be sufficient to overcome the static friction force when the contraction force is reduced to a tenth of the maximum LF. The mechanism of the slide motion could be divided into two processes: separation of the inner wall of the conduit and the gradual separation from other strands due to a gradual reduction of the LF. A tribological analysis revealed that the real contact area increases by 10% when the shear force is applied; this result would help us evaluate the contact resistance between strands of conductors.

Error Estimation in the $T_{cs}$ Measurement of TF Conductors in the SULTAN Facility

The main parameter measured in the tests of the TF conductors for the ITER machine is the current sharing temperature (TCS). In the voltmetric assessment of TCS, the voltages are measured on the conductor jacket, due to the technical difficulties to introduce voltage taps inside the stainless steel conduit. The average voltages measured on the jacket do not exactly correspond to those that arise along the single strands, as shown by the presence of early voltages arising during the current ramp up, when the cable is still in the superconducting phase. It is therefore not trivial to evaluate the difference between the cable and jacket voltages, that gives rise to an experimental error in the measurement of TCS. This paper reports the results of a vast simulation campaign performed with a detailed electromagnetic model of the Cable in Conduit Conductor, in which the origin and the extent of these differences have been investigated, giving an estimate for the experimental error. The impact on measurements of other sources of error such as the signal/noise ratio and the error in the temperature measurements is also reported.

First qualification of ITER Toroidal Field Coil conductor jacketing

The Japan Atomic Energy Agency (JAEA) has the responsibility to procure 25% of the ITER Toroidal Field Coil conductors as the Japanese Domestic Agency (JADA) in the ITER project. The TF conductor is a circular shaped, cable-in-conduit conductor, composed of a cable and a stainless steel conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA started to produce strand, cables and jacket sections and to construct a conductor manufacturing (jacketing) facility in 2008. Following preparation in December 2009 of the jacketing facility, the dummy cable, the jacket sections and fabrication procedures, such as welding, cable insertion, compaction and spooling, JAEA manufactured a 760 m long Cu dummy conductor for process qualification. Into the 760 m long Cu dummy conductor jacketing, JAEA successfully inserted the cable with a maximum force of 32 kN. The outer diameter of the cross section of the spooled conductor was 43.7 ± 0.15 mm, which complies with the ITER target requirement of 43.7 ± 0.3 mm. Following qualification of all manufacturing processes, JAEA has started to fabricate superconducting conductors for the TF coils.

${\rm Nb}_{3}{\rm Sn}$ Strand Characterization for the Nijmegen 45 T Hybrid Magnet

The Nijmegen 45 T hybrid magnet will consist of an inner resistive 33 T resistive magnet and a superconducting 12 T outsert magnet. In the present conceptual design of the layer-wound outsert, the conductor is a Nb3Sn-Cu Cable-In-Conduit Conductor (CICC) with a stainless steel conduit, operating at 4.5 K by a forced flow of supercritical helium. At nominal magnetic field, the operating current is 12.3 kA. The outsert magnet design comprises 3 types of CICC design assuming a void fraction of 29 % and a temperature margin above 1.5 K. The design requires for 0.81 mm diameter Nb3 Sn strands a minimum copper fraction of 50% and a minimum equivalent critical current at 12 T, 4.2 K, ? = 0% of 590 A. A candidate strand considered is a Powder-In-Tube type of NbaSn conductor with 114 filaments and a copper fraction of 55 %. To predict the cable performance in terms of critical current, stability and AC loss under operational conditions to the best of present scaling capabilities, knowledge of the behavior of the critical current Ic(B, T, ?axial), magnetization M(B, dB/dt), stress-strain relation at 300 and 4.5 K and finally Ic as a function of periodic bending and temperature is required. These essential properties, as measured at the University of Twente employing the TiAIV Ic barrel, the PacMan and Tarsis strain devices as well as the integrating magnetometer, are presented and discussed.

Spatial Periodic Bending and Critical Current of Bronze and PIT ${\rm Nb}_{3}{\rm Sn}$ Strands in a Steel Tube

We measured the influence of spatial periodic bending on the critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands that were tightly swaged in a steel tube, imposing a compressive strain, in attempt to simulate the conditions representative for an ITER (international thermonuclear experimental reactor) cable in conduit conductor (CICC). The huge electromagnetic transverse force causes both transverse compressive strain in the strand crossover contacts and bending strain on top of the strain induced by the differential thermal contraction of the various conductor components. For a CICC with stainless steel or Incoloy conduit, the effect of the thermal cool-down strain on the reduction in performance due to periodic bending strain is unknown. We performed periodic bending tests in the TARSIS facility (test arrangement for strain influence on strands) on three samples. The degradation of the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> due to bending appears to be much more severe for a strand swaged in a stainless steel tube than straightforward simulated by available models assuming simply axial strain dependency. It is confirmed by AC loss measurements that the extra degradation can not be attributed to a change in matrix transverse resistivity, possibly affecting the current transfer length, so we believe this is related to the three-dimensional strain state of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn layer.

Evaluation of bending strain dependence of critical current of Nb 3Al conductor for coils with react-and-wind method

In order to clarify the limitation of bending strain in conductor to fabricate the toroidal field coils of DEMO reactor by react-and-wind (R&W) method, the effect of bending strain on the critical currents ( I c) of Nb 3Al cable-in-conduit (CIC) conductor was investigated using the newly developed apparatus which can bend cooled sample from outside of cryostat. The Nb 3Al strand manufactured by jelly roll process was 0.74 mm in diameter with the copper/non-copper ratio of 4.0. The CIC conductor sample which consisted of 54 Nb 3Al strands and 27 copper wires inserted into a stainless steel conduit was 12.4 mm in diameter and 2.3 m in length. The CIC conductor was wound into a torsion coil spring shape with 4.5 turns and 150 mm in diameter. The bending strain and external magnetic field ranges for I c measurement were from 0% to 0.6% and from 9.2 T to 11.3 T, respectively. It was clearly shown that the I c decrease of the CIC conductor by bending is considerably low compared with that of strand, indicating the relaxation of intrinsic strain in Nb 3Al filaments in CIC conductor due to the cabling effect. The I c was not decreased up to 0.4% in bending strain and slightly decreased to 96% of initial I c at 0.55% in bending strain. This indicates that the R&W method with bending strain of 0.6% is fully applied to the coil fabrication method. The furnace size for heat-treatment for R&W method becomes half of wind-and-react (W&R) method.

Effects of Tensile and Compressive Strain on Critical Currents of&lt;tex&gt;$rm Nb_3rm Al$&lt;/tex&gt;Strand and Cable-in-Conduit Conductor

Effects of tensile and compressive strain on critical currents (I c) of Nb3Al strand and cable-in-conduit (CIC) conductor were investigated using a newly developed apparatus. The Nb 3Al strand manufactured by jelly roll process was 0.74 mm in diameter with a copper/noncopper ratio of 4.05. The CIC conductor sample which consists of two Nb3Al strands and one copper wire inserted into a stainless steel conduit was prepared. The effective strain and magnetic field ranges for the CIC conductor sample were from -0.91% to +0.26% and from 6 T to 11 T, respectively. It is clearly shown that the Ic decrease of the CIC conductor sample by longitudinal strain is relieved considerably compared with the strand sample, indicating the relaxation of intrinsic strain in Nb3Al filaments in CIC conductor due to the cabling effect. The relaxation effect is about +0.1% for -0.8% in effective strain of CIC conductor

Development of CICC for KSTAR Superconducting Magnet System

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system adopts a superconducting CICC(Cable-In-Conduit Conductor) type conductor. It consists of 16 TF (Toroidal Field) coils and 14 PF (Poroidal Field) coils and it also uses two different types of CICCs- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$ Nb_3 Sn$</tex> cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A special CICC jacketing system is developed for the KSTAR CICC fabrication: the tube-mill process, which consists of forming, welding, sizing and squaring procedure. The cabling process for TF and PF superconducting cable and the fabrication process of each CICCs (TF CICC and PF CICC) is described. The welding of conduit materials are also discussed. The fabrication results such as the geometrical specification, micro structure and the void fraction will be discussed.

Effect of Conduit Material on CICC Performance Under High Cycling Loads

Recent International Thermonuclear Experimental Reactor (ITER) Model Coils and tests on Nb/sub 3/Sn Cable in Conduit Conductors (CICC) showed a significant and unexpected increase in the broadness of the transition to the normal state, resulting in degradation of superconducting properties. To investigate these phenomena, two CICC samples were built with identical 144 strand cables but different conduit materials. One sample had titanium conduit with low coefficient of thermal expansion, the other had stainless steel conduit. The purpose of this experiment was to study changes in strand properties in the cable (critical current, current sharing temperature, n-value), the effects of cycling and high electromagnetic load, and the effect of the conduit on the CICC performance.

Compressive Pre-Strain in&amp;lt;tex&amp;gt;$rm Nb_3rm Sn$&amp;lt;/tex&amp;gt;Strand by Steel Tube and Effect on the Critical Current Measured on Standard ITER Barrel

The large Cable-In-Conduit Conductors (CICC) designed for the magnet coils in the International Thermonuclear Experimental Reactor (ITER), are composed of Nb/sub 3/Sn strand bundles in a Stainless Steel (SS) or Incoloy conduit. Both, the thermal contraction of the strand composite and the conduit material, define the final pre-strain after cooling down and thus affect the strand critical current (I/sub c/). The transverse forces, introduced when charging a coil, in addition affect the overall strain state due to bending and pinching of strands. Recently, periodic bending tests were applied on strand samples without additional axial compressive pre-strain. Here we explore the method of swaging a SS-tube around a strand to imitate the cool-down strain effect of the conduit. The experimental results of the I/sub c/ measurements at 12 T and 4.2 K are presented for a Nb/sub 3/Sn PIT strand with and without swaged SS tube on both Ti-6Al-4V and SS standard ITER sample holder (barrels). The effect of gluing the sample to the barrel is also investigated. The intrinsic strain state of the samples is verified by measurement of the I/sub c/ versus applied strain with the Pacman spring.

Jacketing and Repair of the KSTAR CICC

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system which consists of 16 TF coils and 14 PF coils adopts a superconducting CICC (Cable-In-Conduit Conductor) type conductor. The KSTAR magnet system uses two different types of CICCs-Nb/sub 3/Sn cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A continuous CICC jacketing system is developed for the KSTAR CICC fabrication and the jacketing system uses the tube-mill process. It consists of forming, welding, sizing and squaring procedures. The welding condition of CICCs and the fabrication process is described. The repair of the CICC is also discussed.

Intelligent-Drillstring Field Trials

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 92477, "Intelligent Drill String Field Trials Demonstrate Technology Functionality," by M.E. Reeves, SPE, Grant Prideco; M.L. Payne, SPE, and A.G. Ismayilov, SPE, BP plc; and M.J. Jellison, SPE, Grant Prideco, prepared for the 2005 SPE/IADC Drilling Conference, Amsterdam, 23-25 February. Intelligent-drillstring components capable of transmitting data at rates as high as 2 Mbit/sec have been developed and successfully tested in commercial drilling applications. The full-length paper details the lessons learned during intelligent-drillstring field trials and focuses on overall network performance during drilling operations, physical handling, and integration of existing downhole measurement-while-drilling (MWD) tools into the network. Introduction Seven years of engineering and development, funded in part by the U.S. Dept. of Energy, has produced an intelligent-drillstring network capable of transmitting data at rates as high as 2 Mbit/sec. This system makes it possible to obtain large volumes of data from existing MWD/logging-while-drilling (LWD) tools almost instantaneously. Additionally, the system design allows data to be transmitted both upward and downward from hundreds of distributed measurement devices, regardless of circulation conditions. Because every node is uniquely identifiable, the location where events occur along the length of the well can be determined. The bidirectional communication architecture means not only that high-speed transmission of downhole data to the surface is possible, but also that commands from the surface to devices downhole can be sent, received, and acted on. A server at the surface can be used to send information to locations on the rig or, in encrypted form, to operations engineers and managers throughout the world. Technology Overview The intelligent-drillstring system comprises conventional drilling tubulars modified to incorporate a high-speed, low-loss data cable running the length of each joint. The cable terminates at unique inductive coils that are installed in the pin nose and corresponding box shoulder of every connection and transmit data across each tool-joint interface. A second-generation, double-shoulder connection provides a good location for coil placement, with each coil installed in a protective groove in the secondary torque shoulder. When two connections are threaded together, the pin-end coil in one joint is brought into close proximity with the box-end coil of another. A carrier signal in the form of an alternating current flowing through the coil in either segment produces a changing electromagnetic field that induces current flow in the other coil, thereby transmitting the signal to the second joint. The data cable is encapsulated inside a pressure-sealed stainless-steel conduit. In a drillpipe configuration, the conduit passes through the body of the tool joint and then enters into the internal diameter of the drillpipe at the internal upset. Fig. 1 provides a cutaway view showing the location of the inductive coils and conduit in a made-up drillpipe connection. The conduit is held under tension in the drillpipe tube, maintaining its position against the tube wall under most conditions and minimizing interference with mud flow or tool deployment through the center of the drillpipe.

05/00628 Development of a 30 m long Nb 3Al superconducting conductor jacketed with a round-in-square type stainless steel conduit for the toroidal field coils in JT-60SC

05/00628 Development of a 30 m long Nb 3Al superconducting conductor jacketed with a round-in-square type stainless steel conduit for the toroidal field coils in JT-60SC

05/00094 Development of a 30 m long Nb 3Al superconducting conductor jacketed with a round-in-square type stainless steel conduit for the toroidal field coils in JT-60SC : Tsuchiya, K. et al. Fusion Engineering and Design, 2004, 70, (2), 131–140

05/00094 Development of a 30 m long Nb 3Al superconducting conductor jacketed with a round-in-square type stainless steel conduit for the toroidal field coils in JT-60SC : Tsuchiya, K. et al. Fusion Engineering and Design, 2004, 70, (2), 131–140