K. Matsui

Japan Atomic Energy Agency, Muramatsu, Niigata, Japan

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Publications (95)91.18 Total impact

  • IEEE Transactions on Applied Superconductivity 06/2015; 25(3):1-4. DOI:10.1109/TASC.2014.2365543 · 1.32 Impact Factor
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    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 06/2014; 24(3):1-5. DOI:10.1109/TASC.2013.2294959 · 1.32 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 06/2014; 24(3):1-4. DOI:10.1109/TASC.2013.2297685 · 1.32 Impact Factor
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    ABSTRACT: The insulation system of the ITER TF coils consists of multi-layer glass/polyimide tapes impregnated a cyanate-ester/epoxy resin. The ITER TF coils are required to withstand an irradiation of 10 MGy from gamma-ray and neutrons since the ITER TF coils is exposed by fast neutron (>0.1 MeV) of 10(22) n/m(2) during the ITER operation. Cyanate-ester/epoxy blended resins and bonded glass/polyimide tapes are developed as insulation materials to realize the required radiation-hardness for the insulation of the ITER TF coils. To evaluate the radiation-hardness of the developed insulation materials, the inter-laminar shear strength (ILSS) of glass-fiber reinforced plastics (GFRP) fabricated using developed insulation materials is measured as one of most important mechanical properties before/after the irradiation in a fission reactor of JRR-3M. As a result, it is demonstrated that the GFRPs using the developed insulation materials have a sufficient performance to apply for the ITER TF coil insulation.
    Joint Conference of the Transactions of the Cryogenic Engineering; 01/2014
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    ABSTRACT: The Japan Domestic Agency (JADA) for ITER will procure toroidal field (TF) coil structures and winding packs and assemble them into a final TF coil configuration. Because the manufacturing schedule of the TF coils is a critical path toward the first plasma of ITER, coil manufacturing must be successful and proceed on schedule. Therefore, risk assessment and management for its manufacturing are essential. JADA performed a risk assessment on the basis of past manufacturing experiences and a risk mitigation policy for ITER-TF coil manufacturing. The results show that risks can be mitigated to a level that we can assure sufficient quality of the TF coil by sound design, manufacturing, and quality management processes that are developed through R&D activities and the use of prototypes.
    Journal of Plasma and Fusion Research 03/2013; 8. DOI:10.1585/pfr.8.2405062
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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. A 760-m Cu dummy conductor was successfully fabricated prior to the manufacture of the actual Nb3Sn conductors. Suitable manufacturing techniques for the long TF conductors were established during fabrication of the dummy conductor. This paper summarizes the technical developments including a high-level quality assurance, leading to the first successful mass production of ITER TF conductor. Approximately 63 tons of Nb3Sn strands were manufactured by the two suppliers by August 2011. This amount corresponds to approximately 60% of the total contribution from Japan. Five sDP conductors (415 m) and six rDP conductors (760 m) to be used in the TF coils were completed as of February 2011. This amount corresponds to approximately 25% of the total contribution (rDP: 24, sDP: 9) from Japan. JAEA is manufacturing one conductor per month under a contract with two Japanese companies for strands, one company for cabling and one company for jacketing. This progress is a significant step in the construction of the ITER machine.
    IEEE Transactions on Applied Superconductivity 06/2012; 22(3):48019-. DOI:10.1109/TASC.2011.2178053 · 1.32 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 06/2012; 22(3):4203005-4203005. DOI:10.1109/TASC.2011.2178379 · 1.32 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 06/2012; 22(3):4803804-4803804. DOI:10.1109/TASC.2012.2188772 · 1.32 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 06/2012; 22(3):4200404-4200404. DOI:10.1109/TASC.2011.2176697 · 1.32 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-. DOI:10.1109/TASC.2011.2178990 · 1.32 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 06/2012; 22(3):4803305-4803305. DOI:10.1109/TASC.2011.2178370 · 1.32 Impact Factor
  • TEION KOGAKU (Journal of the Cryogenic Society of Japan) 01/2012; 47(3):172-177. DOI:10.2221/jcsj.47.172
  • TEION KOGAKU (Journal of the Cryogenic Society of Japan) 01/2012; 47(3):160-165. DOI:10.2221/jcsj.47.160
  • TEION KOGAKU (Journal of the Cryogenic Society of Japan) 01/2012; 47(3):166-171. DOI:10.2221/jcsj.47.166
  • TEION KOGAKU (Journal of the Cryogenic Society of Japan) 01/2012; 47(3):186-192. DOI:10.2221/jcsj.47.186
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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. DOI:10.1088/0029-5515/51/11/113015 · 3.24 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 10/2011; 86:1506-1510. DOI:10.1016/j.fusengdes.2010.12.054 · 1.15 Impact Factor
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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 10/2011; 86:1531-1536. DOI:10.1016/j.fusengdes.2011.01.053 · 1.15 Impact Factor
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    ABSTRACT: The conductors for plasma equilibrium field (EF) coils of JT-60SA are NbTi cable-in-conduit (CIC) conductor with stainless steel 316L jacket. The production of superconductors for actual EF coils started from February 2010. Nine superconductors with 444m in length were produced up to July 2010. More than 300 welding of jackets were performed. Six nonconformities were found by inspections as go gauge, visual inspection and X-ray test. In order to shorten the manufacturing time schedule, helium leak test was conducted at once after connecting the long length jacket not just after the welding. The maximum force to pull the cable into jacket was about 7.6kN on average. The mass flow rates of 9 conductors showed almost same values indicating that there are no blockages in the conductors. The measured current sharing temperature agreed with the expectation values from strand performance indicating that no degradation was caused by production process. The coupling time constants of conductors ranged from 80 to 90ms which are much smaller than the design value of 200ms.
    Fusion Engineering and Design 10/2011; 86(6):1432-1435. DOI:10.1016/j.fusengdes.2011.01.028 · 1.15 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; 21(3-21):1982 - 1986. DOI:10.1109/TASC.2010.2093488 · 1.32 Impact Factor

Publication Stats

584 Citations
91.18 Total Impact Points

Institutions

  • 1998–2014
    • 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
  • 2001–2003
    • Tohoku University
      • Institute for Materials Research
      Miyagi, Japan
  • 2002
    • Seikei University
      Edo, Tōkyō, Japan