K. Matsui

Japan Atomic Energy Agency, Muramatsu, Niigata, Japan

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Publications (76)77.96 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The authors performed some trials on TF coil fabrication and started first TF coil fabrication. In the trial on radial plate (RP) fabrication, flatness of machined RP section satisfied the target flatness of 1 mm and laser welding technique for joining RP sections was developed. The RP manufacturing plan is revised based on these trial results and fitting method of heat-treated conductor, whose length changes by its heat treatment, is also decided in this plan. Fabrication of the RP materials for the first TF coil has been completed and they satisfied the requirements, such as yield strength of 900 MPa at 4K. Preparation and commissioning of the tooling are in progress.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3):1-5. · 1.20 Impact Factor
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    ABSTRACT: To evaluate presences of performance degradation due to strand bending in Nb3Sn cables, methods for investigating strand bending in Nb3Sn cables were developed by JAEA and demonstrated for the He-inlets of the ITER toroidal field coils. Conductor elongation and residual strain during the reaction heat treatment were measured. In addition, high-resolution X-ray computerized tomography was used to visually search for strand bending in the Nb3Sn cable. As a result, no large strand bending was observed.
    IEEE Transactions on Applied Superconductivity 01/2014; 24(3):1-4. · 1.20 Impact Factor
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    ABSTRACT: Japan Atomic Energy Agency (JAEA) was the first to start the mass production of the TF conductors (jacketing) in March 2010 among the 6 parties who are procuring TF conductors in the ITER project.
    IEEE Transactions on Applied Superconductivity 06/2012; 22(3):48019-. · 1.20 Impact Factor
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    ABSTRACT: The performances of six ${\rm Nb}_{3}{\rm Sn}$ conductors for the ITER Toroidal Field coils were tested. Four of them showed similar degradation rates of their current sharing temperatures $T_{cs}$ over 1,000 electromagnetic cycles. By contrast, two of them showed sharp $T_{cs}$ degradations at 50 cycles, after which their slopes became similar to those of the other four conductors. These two cables seemed to shrink under high magnetic fields during the first 50 cycles, which caused the sharp $T_{cs}$ degradation. This shrinkage might arise from a decline in cable rigidity due to, for example, the deformation of strands or the breakage of the ${\rm Nb}_{3}{\rm Sn}$ filaments. The four mass-produced conductors had roughly the same AC loss before cycling. After 1,000 cycles, the AC losses of all the conductors decreased markedly to less than half of those before cycling, and the values became approximately the same. After the test campaign, the destructive inspection of two of the conductors made it clear that the conductor had shrunk by about 520 ppm under the high magnetic field during the test. It was also clarified that some strands were visibly deformed under the high magnetic field, whereas those under the low magnetic field did not look distorted. This plastic deformation of the strands could be one of the major reasons for the $T_{cs}$ degradation with cyclic operation.
    IEEE Transactions on Applied Superconductivity 06/2012; 22(3):48048-. · 1.20 Impact Factor
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    ABSTRACT: The authors performed one-third scale trials of the conductor winding, the heat treatment and the insulation/impregnation to demonstrate and optimize fabrication procedure of TF coil. In this trial, accuracy of conductor length measurement system was confirmed in the winding trial. The conductor elongation and winding deformation due to the heat treatment were evaluated in the heat treatment trial. And the procedure of insulation and impregnation was established through the insulation/impregnation trial, and the insulation condition was fixed.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):4203005-4203005. · 1.20 Impact Factor
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    ABSTRACT: Japan Atomic Energy Agency (JAEA) started sub- and full-scale trials to qualify and optimize manufacturing procedure of ITER TF coil from March 2009 under the contract with Toshiba. As major outcome of these trials, feasibility of high accuracy of winding, prediction of the conductor elongation due to heat treatment and radial plate manufacture is confirmed. Therefore, JAEA can mostly establish manufacturing plan for the TF coil and then, start the first TF coil procurement from 2013, following to full demonstration through manufacturing a dummy double-pancake in 2012.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):4200404-4200404. · 1.20 Impact Factor
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    ABSTRACT: A method for evaluating the critical current of conductors is discussed in the context of the relationship between the electric field of the conduit surface and the superconducting cable in CIC conductors used for nuclear fusion reactors. The potential detected by voltage taps located on the surface of the conduit is the average potential of strands that have contact with the virtual surface area of the cable. This area is defined in terms of contact resistance between the conduit and strands as well as conduit resistance. Considering that a strand is uniformly distributed in a conductor due to the cabling effect, it is possible to replace in calculations the distribution of the electric field of a strand along the length of the conductor with the distribution of a cross section of the conductor, a replacement which renders possible statistical approach. As a result, the voltage measured by a pair of voltage taps located along the length of the conductor can be expressed in terms of a general formula which establishes a relationship between the electric field of the conduit surface and the superconducting cable including statistic errors. Using this formula, the electric field of the cable and the consequent superconducting properties of the conductor may be estimated with an acceptable degree of accuracy. Assessment of the experimental results and performance of the ITER conductors are introduced with discussion of temperature measurement issue, and the validity of the formula is discussed.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):4803804-4803804. · 1.20 Impact Factor
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    ABSTRACT: Japan Atomic Energy Agency (JAEA) has fabricated and tested the four conductor samples composed of high performance ${\rm Nb}_{3}{\rm Sn}$ strands manufactured by the bronze-route process for the ITER Central Solenoid (CS) conductor. The current sharing temperature (Tcs) electrically assessed at 45.1 K and 10.85 T along the cycling loading at 48.8 kA and 10.85 T initially were 6.0 K and 6.1 K, and then 5.3 K and 5.5 K after 6000 cycles for the first SULTAN sample named JACS01, respectively. As results of second SULTAN sample named JACS02, the Tcs values initially were 7.2 K and 6.8 K, and then 6.6 K and 6.1 K after 10000 cycles for each conductor, respectively. The Tcs degradation was not saturated at the end of the test campaign. From the destructive observation, the large bending at the low transverse loading side in the high field zone was observed. The strand buckling and accumulating by slipping between the cable and the jacket are considered.
    IEEE Transactions on Applied Superconductivity 01/2012; 22(3):4803305-4803305. · 1.20 Impact Factor
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    ABSTRACT: The design and manufacture of Nb3Sn conductors for ITER toroidal field (TF) coils have many technical challenges. Although it was demonstrated in the ITER model coil project that the conductors have a sufficiently high performance and the engineering design is valid, unexpected issues arose. Through both theoretical and experimental efforts improved conductors were developed. The Japan Atomic Energy Agency started to procure improved conductors for TF coils as part of the ITER project. Because the required tonnage of Nb3Sn strands is quite large compared with past experience and the required superconducting performance is higher than that of the model coils, quality control techniques are very important for the successful manufacture of the strands. Approximately 60 ton of Nb3Sn strands have been successfully completed under a severe quality control regimen and all strands meet ITER specifications. This paper summarizes the technical developments leading to the first successful mass production of ITER TF conductors.
    Nuclear Fusion 10/2011; 51(11):113015. · 2.73 Impact Factor
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    ABSTRACT: The Japan Atomic Energy Agency (JAEA) developed ITER TF Nb<sub>3</sub>Sn conductors that fulfill ITER requirements and has commenced fabricating the conductors to be used in the ITER TF coils. As a qualification of conductor fabrication, two full-size conductor samples, named as JATF4, were prepared and tested by the SULTAN facility at CRPP in Switzerland. Temperature sensors and voltage taps were attached on the three meter-long conductor samples to measure the current sharing temperature (Tcs). Measurements were performed at the beginning of the testing campaign, during cyclic test, and at the end of the campaign following a warm up and cool down. The Tcs values electrically assessed by the agreed procedure at outer magnetic fields of 10.78 T initially were 6.5 K and 6.2 K, and then 6.1 K and 6.0 K at the end of the campaign for each conductor, respectively. These results demonstrate that the conductors have a sufficient Tcs margin to satisfy the ITER TF conductor criterion of 5.7 K, and conductor fabrication is qualified. Details of the test results are presented and discussed.
    IEEE Transactions on Applied Superconductivity 07/2011; · 1.20 Impact Factor
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    ABSTRACT: 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.
    Fusion Engineering and Design. 01/2011; 86:1506-1510.
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    ABSTRACT: The Japan Atomic Energy Agency (JAEA) is responsible for the procurement of 9 TF coils as the Japanese Domestic Agency in the ITER project. Small- and full-scale trials are being performed to demonstrate and optimize fabrication procedures before starting production of the TF coils. JAEA is carrying out the conductor winding and insulation/impregnation trials in advance of the other trials because they represent key processes in TF coil manufacture. Mechanical tests of the conductors are performed to ascertain their bending behavior during winding. The commissioning of tooling for the one-third scale winding already is complete. The winding test was conducted using a specially developed winding head which resulted, based on mechanical test results, in achieving a curvature of the bent conductor in line with expectations. Impregnation trials using the acrylic and metallic model were performed to demonstrate the impregnation procedure and the applicability of bonded glass–polyimide tape, which is expected to facilitate the winding of the insulation tape around the conductor. Results demonstrate the suitability of the bonded glass–polyimide tape for the impregnation procedure.
    Fusion Engineering and Design. 01/2011; 86:1531-1536.
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    ABSTRACT: The superconducting properties of strands are very sensitive to strain. Measuring internal strain of in Cable-In-Conduit Conductors (CICC) is important for evaluating the superconducting performance of CICC. Internal strain can be determined by neutron diffraction measurement using Takumi of J-PARC. Neutron diffraction measurement becomes a strong tool for evaluating directly the internal strain of in CICC. Index Terms—CICC, , ITER, neutron diffraction.
    IEEE Transactions on Applied Superconductivity 01/2011; 21(3):2028-2031. · 1.20 Impact Factor
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    ABSTRACT: The authors performed trials and studies to solve the remaining technical problems for manufacturing the ITER Toroidal Field (TF) coil. Cover plate (CP) welding deformation of a side double pancake may achieve specified tolerances with correction of a long wave distortion through the use of a small load, although complicated welding operations are required. In addition, JAEA developed a new procedure for manufacturing a CP at a reduced cost. Straight and curved CPs are fabricated by hot-rolling and cold-drawing and bending the straight CP with sufficient accuracy. Applying these results, JAEA has started procurement of the TF coil, beginning with qualification trials. Manufacture of a full-scale regular RP, finalization of a manufacturing plan and drawings and design of tooling will be completed by the middle of 2011.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
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    ABSTRACT: Japan Atomic Energy Agency has developed Nb3Sn strands for the ITER magnet, whose critical current density is about 1.4 times as large as that of ITER CS Model Coil. The magnetic field, temperature, and strain dependence on the critical current (Ic) of the strands were measured with apparatus that were developed by the authors. The strain properties in particular were investigated in detail, with strain tensor analysis revealing that the upper critical field dependence on strain can be naturally formulated using a high order polynomial terms of strain taking into account residual strain due to thermal contraction difference inside the strand and strain applied externally. A correlation formula for field, temperature, strain and Ic of the strand is discussed and presented. Recent results of fabricating strands for ITER TF coil are then finally provided.
    IEEE Transactions on Applied Superconductivity 07/2010; · 1.20 Impact Factor
  • Norikiyo Koizumi, Kunihiro Matsui, Kiyoshi Okuno
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    ABSTRACT: The critical currents of the Japanese ITER TF conductors made through an internal-tin and bronze process were preliminarily estimated to be about 5.7 K, which approximates the design value of 5.7 K, and about 6.1 K, respectively, at 68 kA and 11.8 T using a short conductor sample. To investigate the influence of the current distribution in the sample conductor, a simulation was performed using a lumped circuit model of a cable and static electrical field model for jackets. The simulation results show that a large, non-uniform current distribution is established due to magneto-resistance of the copper in the joint and an imbalance of contact resistance of the strands to the copper and by poor soldering between the copper shoes, results which make a precise evaluation of the critical current performance difficult. The analytical results indicate that the current sharing temperature of the internal-tin and bronze process conductors is expected to be 6.0 K and 6.7 K, respectively, when the current distribution is uniform. In addition, solder filling of the joints makes the current distribution uniform due to the normal resistance in the high field zone, and the current sharing temperature can be estimated as almost the same as when the current distribution is uniform. The other possible solution is to use a thin copper plate with a low RRR to reduce the influence of magneto-resistance and any non-uniformity in contact resistance. Conductor performance is under-estimated in this case because the non-uniform current distribution still remains. However, the reduction in the estimated current sharing temperature is expected to be a few hundred milli-Kelvins, which seems acceptable as a margin in a qualification trial.
    Cryogenics 01/2010; · 1.17 Impact Factor
  • TEION KOGAKU (Journal of the Cryogenic Society of Japan) 01/2010; 45(4):135-147.
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    ABSTRACT: ITER PFCI has been manufactured in the Europe and installed into the ITER Test Facility in Naka, Japan. The conductor is NbTi cable-in-conduit conductor with thick square stainless steel jacket and almost identical with the design of the ITER PF coils. The main objective of this test is the characterization of the conductor and joints at the conditions relevant to the ITER PF coil operation. Intermediate joint is located in the winding at relatively high field to examine its performance. The main items in the PFCI test program are thermo-hydraulic test, DC mode test, cyclic test and pulse mode test. The PFCI and CSMC were successfully cooled down to cryogenic temperature within 450 hours. The test of the PFCI was performed from May to August 2008. The key technology of the installation, the test methods and procedures, and some preliminary results of cool-down are described in this paper.
    IEEE Transactions on Applied Superconductivity 07/2009; · 1.20 Impact Factor
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    ABSTRACT: A Nb<sub>3</sub>Al strand, produced by the ldquorapid-heating, quenching and transformation annealing (RHQT)rdquo process, has been developed in collaboration between JAEA and NIMS aiming at application to the conductor in a fusion DEMO reactor. A detailed description of critical current characteristics of the Nb<sub>3</sub>Al RHQT strand may assist in predicting accurate conductor performance. Calculations of the critical current density are adjusted to 5 scaling laws. Advantages of the newly developed strand compared to the Nb<sub>3</sub>Sn ITER strand and the Nb<sub>3</sub>Al Insert strand include improved strain tolerance and a higher current density at around 16 T. Performance parameters of the Nb<sub>3</sub>Al RHQT strand include 450 A/mm<sup>2</sup> at 15.9 T, 5.7 K and -0.4%. These performance parameters fulfill the requirements of the TF conductor of the fusion DEMO reactor. Therefore, the Nb<sub>3</sub>Al RHQT strand represents an improved performance with prospective application in the fusion DEMO reactor. In addition, the Nb<sub>3</sub>Al RHQT strand has the potential to enhance further the critical current density.
    IEEE Transactions on Applied Superconductivity 07/2009; · 1.20 Impact Factor
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    ABSTRACT: Many full size conductors for the ITER TF coils have been tested at the SULTAN test facility in Switzerland for conductor qualification. JAEA tested two samples and two kinds of Nb<sub>3</sub>Sn strands were evaluated through the tests. Now another sample named JATF3 has been tested, which uses two other kinds of Nb<sub>3</sub>Sn strands. The strands satisfy the critical current density J<sub>c</sub> requirement, but results of the conductor test were lower than our expectation. After the test, JAEA has been investigating the reason by X-ray CT scan and destructive inspection, and has found a possible reason.
    IEEE Transactions on Applied Superconductivity 07/2009; · 1.20 Impact Factor

Publication Stats

355 Citations
77.96 Total Impact Points

Institutions

  • 2003–2014
    • Japan Atomic Energy Agency
      • • Quantum Beam Science Directorate
      • • Nuclear Science and Engineering Directorate
      Muramatsu, Niigata, Japan
  • 2004
    • ITER
      Marsiglia, Provence-Alpes-Côte d'Azur, France
  • 2002
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan