Fabrication of MgB 2 superconducting wires as low activation superconducting materials for an advanced fusion reactor application
ABSTRACT Magnesium diboride (MgB2) superconducting wires are interesting as alternative conductor of Nb-based superconducting wire applying for the advanced nuclear fusion reactor from viewpoint of decay time of induced radioactivity. However, Jc property of MgB2 wire is insufficient for alternative material of Nb-based superconductor, and it is necessary to improve further Jc property. In order to improve Jc property, we tried to fabricate the several trace amounts of Cu addition MgB2/Fe-sheathed wires through PIT process using Mg2Cu as Cu addition source. Tc values of Cu addition samples were higher than those of non-Cu addition samples and they were improved with increasing amount of Cu addition. On the other hand, core Jc value were decreased with increasing amount of Cu addition and the maximum core Jc values were estimated to be over 100A/mm2 at 4.2K under 8T for 1 and 3at% Cu addition sample.
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ABSTRACT: We investigated the effect of tritium upload in the dense, polycrystalline MgB2 superconductor for 2 and 216 h. One basic property, the critical temperature Tc, slowly changes in time but is independent of the duration of tritium uptake. Immediately after tritiation, Tc shows a slight increase to 39.1 K but decreases to the critical temperature of the untritiated (pristine) sample, Tc = 38.8 K, after 370 days. The critical current density is strongly dependent on the tritium upload time, mainly at high magnetic fields. The underlying physics is discussed. This behaviour makes the use of MgB2 based conductors advantageous in tritium environments like fusion reactors.Superconductor Science and Technology 04/2013; 26(4). DOI:10.1088/0953-2048/26/4/045014 · 2.80 Impact Factor
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ABSTRACT: Applicability of 1 GW class hybrid energy transfer line of hydrogen and electricity is investigated in this report. Hydrogen refrigeration station is placed on every 10 km of the unit section. The rated current is 10 kA, and operation voltage is 100 kV (+ 50 kV and −50 kV for ground). Delivery capacity of the liquid hydrogen is 100 tons per day. The HETL consists of the SC cable, electrical insulation layer, channel for liquid hydrogen, inner corrugated tube, vacuum space for thermal insulation and outer corrugated tube. The special multi-filamentary MgB2 wire was developed to improve the Ic performance against bending strain. When the pressure of liquid hydrogen increases, boiling temperature of liquid hydrogen becomes high. Pressurization of liquid hydrogen enables to expand operation temperature region of the MgB2 cable, and to absorb the head loss of the installation route. To obtain the operation temperature from 20 K to 25 K, pressure of liquid hydrogen from 0.4 to 0.6 MPa was chosen. When the heat leak into the liquid hydrogen is 1.0 W/m (expected value), the temperature at the outlet becomes 21.8 K. It was confirmed that this HETL is one of the attractive energy transportation system which combines hydrogen fuel and SC power transmission.Journal of Physics Conference Series 07/2010; 234(3):032064. DOI:10.1088/1742-6596/234/3/032064
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ABSTRACT: Applicability of 1 GW class hybrid energy transfer line of hydrogen and electricity is investigated. Target distance of hybrid energy transfer line is 1000 km. Hydrogen refrigeration station is placed on every 10 km of the unit section. The rated current and withstand voltage of the dc power line are 10 kA and 100 kV, respectively. Capacity of the liquid hydrogen transportation is 100 tons per day. Transfer line consists of the superconducting (SC) cable, space for liquid hydrogen, electrical insulation layer, vacuum space for thermal insulation, and cryogenic envelopes. High Jc performance in a liquid hydrogen temperature requires for the SC cable. The MgB2 wire is one of the potential candidates for this system as well as BSCCO or YBCO tapes. To keep the liquid state of hydrogen anywhere in the unit section, the temperature and pressure of the inlet point were selected to 17 K and 0.4 MPa, respectively. When the heat leak into the liquid hydrogen was 1.0 W/m (expected value), the temperature at the outlet became 18.1 K. Total power consumption of the 10 kW class refrigerator is estimated to 660 kW. The total power consumption for the hybrid energy transfer line of 1000 km length becomes 132 MW. This value is equivalent to 13.2 % to the transport capacity of 1GW.Journal of Physics Conference Series 01/2008; DOI:10.1088/1742-6596/97/1/012167