1,721,147 research outputs found
4C code analysis of high-margin quench propagation in a DEMO TF coil
No full textIn the frame of the European DEMO reactor activities, Work Package MAG, superconducting Toroidal Field (TF) coils composed by a graded (Nb3Sn + NbTi) winding pack (WP) without radial plates, encapsulated in a steel casing, are under analysis. The ENEA WP design consists of double-layer wound rectangular cable-in-conduit conductors (CICC), for which operational as well as accidental transients must be carefully investigated. The paper presents the application of the state-of-The-Art thermal-hydraulic code 4C to the analysis of the quench propagation inside the WP proposed in 2014 by ENEA. The quench is conservatively initiated at the location of the maximum temperature margin and the voltage, normal zone, hot spot temperature and maximum pressure evolutions in the WP are computed, highlighting the role of thermal coupling inside the WP. © 2015 IEEE
Design, Manufacture and Test of a 82 kA ReactWind TF Conductor for DEMO
No full textThe Toroidal field coils (TFC) of the EUROFusion DEMO reactor call for Nb3Sn conductor with high field and high current. Another major requirement is cost-effectiveness, to keep the ratio of investment to electric power in the same range of the competing energy sources (fission, hydro, coal, gas, etc.). The TFC proposed by the Swiss Plasma Center (SPC) is based on a double-layer Nb3Sn/NbTi winding. A react-and-wind flat cable is the core of the Nb3Sn conductor, with six grades to minimize the cost and maintain a roughly constant temperature margin of 1.5 K over the winding cross section. A short length section of the high grade Nb3Sn conductor has been manufactured using relevant industrial cabling equipment. One hundred kilograms of 1.5-mm Nb3Sn strand has been procured at WST with average Jc up to 15% higher than specified (Jc≥ 1000A/mm2 at 12 T/4.2 K). A dedicated cabling line has been set up at TRATOS cavi (Italy), producing over 350 m of dummy cable and about 13 m of superconducting cable. The assembly of the cable into a conduit by longitudinal laser welding of two steel profiles is demonstrated, including the QA procedures. A test sample has been prepared at SPC by heat treating straight sections of the cable and encasing it into a steel jacket after the heat treatment to minimize the thermal strain. The test was carried out in three test campaigns at the EDIPO facility at SPC. The test program includes Dc performance at the relevant operating conditions. An assessment of the conductor test results in terms of strand performance suggests that the applicable thermal strain is less than -0.33%. The performance is stable upon load cycles. © 2002-2011 IEEE
Design of large size, force flow superconductors for DEMO TF coils
No full textThe DEMO plant will demonstrate by mid-century the feasibility of electric power generation by nuclear fusion. In the scope of design studies coordinated by the European Commission, CRPP and ENEA are developing two force flow conductor layouts as candidates for the toroidal field (TF) coils of DEMO. The operating conditions include 82 kA operating current and 13.5 T peak field, placing the DEMO TF conductor at substantially higher performance compared to the ITER TF (68 kA/11.5 T). The innovative winding layout is graded, layer wound with Nb3Sn/NbTi hybridization for both conductor designs, aiming at minimizing the size and the cost of the superconductor: one of the conductors is a wind and react cable-in-conduit conductor with reduced void fraction and has a rectangular shape. The other conductor is a react and wind flat cable with copper segregation and thick conduit assembled by longitudinal weld. The conductor designs were first drafted in 2012 and reviewed in 2013 based on a first round of assessments and on an updated requirements catalog. The manufacture of full-size prototypes is planned in 2014. © 2013 IEEE
Thermal-Hydraulic Test and Analysis of the ENEA TF Conductor Sample for the EU DEMO Fusion Reactor
No full textThe ENEA conductor for the EU DEMO Nb3Sn toroidal field (TF) magnets, cooled by supercritical He, features a rectangular cross section with two small pressure relief channels ('holes'), separated from the cable bundle by means of a flat spiral, twisted together with the last cabling stage. A well-instrumented short sample of the ENEA TF conductor has been tested in SULTAN at SPC, Villigen (Switzerland) in 2016, aimed at its thermal-hydraulic characterization, and the test results are presented here. A correlation for the friction factor in the small holes is derived, best fitting the results of a set of computational fluid dynamics simulations. The new correlation (combined with existing correlations for the He friction factor in the bundle region) is shown to allow a proper reproduction of the measured hydraulic characteristic of the conductor. The heat slug propagation tests are used to calibrate the hole-to-bundle heat transfer coefficient in the 4C thermal-hydraulic code and to estimate the characteristic length for the homogenization of the He temperature on the conductor cross section, following a localized thermal perturbation. © 2002-2011 IEEE
Overview of Progress on the EU DEMO Reactor Magnet System Design
No full textThe DEMO reactor is expected to be the first application of fusion for electricity generation in the near future. To this aim, conceptual design activities are progressing in Europe (EU) under the lead of the EUROfusion Consortium in order to drive on the development of the major tokamak systems. In 2014, the activities carried out by the magnet system project team were focused on the toroidal field (TF) magnet system design and demonstrated major achievements in terms of concept proposals and of consolidated evaluations against design criteria. Several magnet system RD activities were conducted in parallel, together with broad investigations on high temperature superconductor (HTS) technologies. In this paper, we present the outcomes of the work conducted in two areas in the 2014 magnet work program: 1) the EU inductive reactor (called DEMO1) 2014 configuration (power plant operating under inductive regime) was the basis of conceptual design activities, including further optimizations; and 2) the HTS RD activities building upon the consolidated knowledge acquired over the past years. © 2016 IEEE
Development of a Thermal-Hydraulic Model for the European DEMO TF Coil
No full textIn the framework of the 'roadmap to fusion electricity by 2050,' the design of the European DEMO machine strongly relies on available technologies. The superconducting toroidal field (TF) magnets will be built using available low-temperature superconducting strands; the ENEA winding pack (WP) proposal will exploit graded layer-wound rectangular conductors, whose design is ongoing. The WP will be encapsulated in a stainless steel casing, whose cooling has not yet been designed. In this paper, we present the thermal-hydraulic (TH) model of an entire TF coil for the European demonstration power plant DEMO. Two cooling options are proposed and investigated for the casing, whereas for the WP, the ENEA design, with multiple low-impedance hydraulic channels, is considered. The thermal coupling between WP and casing is parametrically included in the model. The TH behavior of a TF coil (WP + casing) during a plasma burn is presented and discussed, comparing the two cooling options of the casing. © 2002-2011 IEEE
Magnetization loss for stacks of ReBCO tapes
No full textThe AC loss measurements of the high temperature superconductor (HTS) cable prototype in the EDIPO test facility motivated detailed investigations of the loss contributions from the tape, strand and cable stages of the HTS fusion conductor design proposed at the Swiss Plasma Center. As an initial step of the task, magnetization tests of soldered stacks of HTS tapes were carried out at temperatures of 5 and 77 K and magnetic fields up to 12 T using the vibrating sample magnetometer technique. The influence on the magnetization loss of the number of tapes, width of the tape, field's orientation and tape's manufacturer is studied experimentally performing both the major and minor magnetization loops with different ramp rates of the applied magnetic field. In order to validate the test results, a numerical model is developed and presented in this work. From the numerical model we also deduced an analytical approach for the magnetization loss in the stacks of tapes with arbitrary number of tapes in the critical state model. Comparison between the measured and estimated magnetization loss of the cable prototypes is reported as well
The Effect of Hydrostatic Pressure on the Superconducting and Structural Properties of Nb 3Sn: Ab-initio Modeling and SR-XRD Investigation
No full textWe report on the investigations of the structural and superconducting properties of Nb3Sn in the GPa range by angular dispersive synchrotron X-ray diffraction and ab-initio calculations based on density functional theory. X-ray Diffraction experiments were carried out on Nb3Sn technological samples to explore the equation of state at room temperature and at pressures up to 43.5 GPa: We observe an anomaly in the P-V curve in the region 5-10 GPa. The ab-initio calculated lattice parameter of Nb3 Sn as a function of pressure has been used as an input for the calculation of the phonon dispersion curves and of the electronic band structures along different high-symmetry directions in the Brillouin zone. The critical temperature has been calculated as a function of the hydrostatic pressure by means of the Allen-Dynes modification of the McMillan formula: We found that its behavior is dictated mostly by the electronic contribution, but evident anomalies up to 6 GPa arise from phonons. These findings are a clue that Nb3 Sn could have some structural instabilities with impact on its superconducting properties when subjected to a pressure of a few GPa and they represent an important step to understand and optimize the performances of Nb3Sn materials under the hard operational conditions of high field superconducting magnets. © 2002-2011 IEEE
Progressing in cable-in-conduit for fusion magnets: From ITER to low cost, high performance DEMO
No full textThe performance of ITER toroidal field (TF) conductors still have a significant margin for improvement because the effective strain between -0.62% and -0.95% limits the strands' critical current between 15% and 45% of the maximum achievable. Prototype Nb3Sn cable-in-conduit conductors have been designed, manufactured and tested in the frame of the EUROfusion DEMO activities. In these conductors the effective strain has shown a clear improvement with respect to the ITER conductors, reaching values between -0.55% and -0.28%, resulting in a strand critical current which is two to three times higher than in ITER conductors. In terms of the amount of Nb3Sn strand required for the construction of the DEMO TF magnet system, such improvement may lead to a reduction of at least a factor of two with respect to a similar magnet built with ITER type conductors; a further saving of Nb3Sn is possible if graded conductors/windings are employed. In the best case the DEMO TF magnet could require fewer Nb3Sn strands than the ITER one, despite the larger size of DEMO. Moreover high performance conductors could be operated at higher fields than ITER TF conductors, enabling the construction of low cost, compact, high field tokamaks. © 2018 IOP Publishing Ltd
The role of stoichiometry in superconducting Nb1-βSnβ: Electronic and vibrational properties from ab initio calculations
No full textUsing first principles calculations based on density functional theory, the electronic, vibrational and superconducting properties of compounds with different stoichiometry ratios in the A15 phase have been studied. To this purpose, the λ mass enhancement parameter, which determines the superconducting critical temperature through the Allen-Dynes modification of the McMillan formula, has been explicitly calculated in the context of the density functional perturbation theory that allows the calculation of the matrix elements of the electron-phonon interactions at different compositions related to the Sn content. Our results provide a better understanding of the inhomogeneous composition of one of the most widely employed low-temperature superconductors, evidencing the electronic properties and the phonon modes that are responsible for the critical temperature degradation as the Sn concentration is varied. © the Owner Societies 2016
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