In Japan, 9 ITER TF coils for Japan and 10 TF coil cases (CCs) for EU are procured from two suppliers. In the second manufacturing line (ML), some of manufacturing procedures were optimized and/or ...rationalized from lessons learned from the experiences in the first ML. These efforts contributed to simplification and acceleration of the fabrication of the ITER TF coil in the second ML and then, the first ITER TF coil has been completed in May 2021 in the second ML. In addition, the most challenging processes in TF coil fabrication such as very accurate current center line positioning and proper gap between a winding pack (WP) and CC, more than 4 mm were achieved in assembly of WP and CC, as well as the first ML. These results justified the validity of the optimized and rationalized manufacturing procedure in the second ML. Therefore, we can say that manufacturing in both first and second MLs in Japan has become stable. Actually, four and two TF coils have been completed in the first and second MLs in Japan, respectively.
The Japan Atomic Energy Agency is responsible for procuring all amounts of central solenoid (CS) conductors for International Thermonuclear Experimental Reactor, including CS jacket sections. The ...conductor is cable-in-conduit conductor with a central spiral. A total of 576 Nb 3 Sn strands and 288 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.08 mm. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m, and 6400 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 100 kg, respectively. Since the CS conductor suffers 60000 cycles of high electromagnetic force in the lifetime, severe requirements were specified for jacket sections in terms of not only high mechanical performance at 4 K but also of the size of initial defects in the jacket section. The minimum allowable defect size is estimated to be 2 mm2 × 0.2 mm by linear elastic fracture mechanics. Eddy current test (ECT) and phased array ultrasonic test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside the jacket section can be detected by PAUT. These technologies and the inspected results of more than 700 jacket sections are reported in this paper.
Japan Atomic Energy Agency has manufactured JJ1, strengthened 316LN (ST316LN) forgings, ST316LN hot rolled plates to demonstrate for mass production of the materials for ITER Toroidal Field (TF) coil ...structure. Tensile, fracture toughness and fatigue test samples were taken from the products and tested to demonstrate mechanical properties of mass production material. Averaged value of 0.2% yield strength for the JJ1, ST316LN forgings and the ST316LN hot rolled plate are 1126
MPa, 1078
MPa and 1066
MPa, respectively. The JJ1 and ST316LN forgings showed uniform ultimate tensile strength (UTS) distribution along the thickness direction. In the ST316LN hot rolled plate with thickness of 200
mm, UTS showed some scattering caused by coarse gains which was locally observed at one quarter thickness. However, the mixed grain condition would be solved by modification of forging process, followed by a hot roll process. Measured fracture toughness
K
IC(J) was more than
200
MPa
m
for all products. A fatigue characteristics (S–N) of ST316LN have been measured at 4.2
K and design S–N curve were determined. It was confirmed that ST316LN has enough margins for a cyclic operation of 384
MPa with 3
×
10
4 cycles on the TF coil case. Therefore, the ITER mechanical requirements for TF coil structure material will be achievable in actual JJ1 and ST316LN manufacturing.
Under the International Thermonuclear Experimental Reactor (ITER) project, the Japan Atomic Energy Agency (JAEA) is procuring all of the Nb 3 Sn conductors for the Central Solenoid (CS). The CS ...consists of six vertically stacked modules. The height and outer diameter of the CS are approximately 13 m and 4 m, respectively. The CS has a circular five stage cable. All of approximately 43 km of Nb 3 Sn CS cables will be manufactured in Japan. Before mass-production start, the jacketed cable conductors should be tested in the SULTAN facility in Switzerland to confirm their superconducting performance. The original cabling design had relatively long twist pitches and is referred to as the normal twist pitch (NTP) conductor. The NTP conductor test results revealed decreasing the current sharing temperature (Tcs) with increasing number of electro-magnetic (EM) load cycles. Therefore, a short twist pitch (STP) design was proposed and the STP conductors were also tested. The STP conductor results showed that the Tcs is stable during EM cyclic load tests. Because the conductors with STP have a smaller void fraction in the cable area than those with NTP, a higher compaction ratio during cabling is required and the possibility of damage on strands increases. The STP cable technology was developed in collaboration among Japanese cabling suppliers and JAEA. Several key technologies will be described in this paper.
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