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 Nb 3 Sn 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 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.
The performances of six Nb 3 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 Nb 3 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.
The performance of two conductors for the ITER central solenoids was tested. The current sharing temperatures were measured over 17 050 electromagnetic cycles, including four thermal cycles between ...4.2 K and room temperature. declined almost linearly over the 10 000 rated electromagnetic cycles. was nearly constant for 70% of the rated electromagnetic cycles, which implies the existence of a fatigue limit in the conductors. For 85% of the rated cycles, a very sharp degradation of approximately 0.2 K occurred. Some type of large deformation of strands, such as buckling, may have caused this sharp degradation. The effective strain degraded linearly with the electromagnetic force on the cable. The gradient after 10 000 cycles was 1.5 times greater than that before cycling. After 10 000 cycles, the ac losses of both conductors considerably decreased to less than half of those before cycling. These ac losses before cycling were less than a fourth of those of toroidal field conductors. After the test campaign, destructive inspection of the conductor clarified that on average, the distribution of residual strain along the cable was almost uniform at 32 ppm. It was also clarified that some strands were visibly deformed under a high magnetic field, whereas strands under a low magnetic field did not appear to be deformed. The deformations of the central solenoid cable were larger and wavier in subcables than those observed in the toroidal field cable. This plastic deformation of the strands could be one of the major reasons for the degradation during cyclic operation.
The Japan Atomic Energy Agency (JAEA) has developed jacketing technologies for ITER Toroidal Field (TF) and Central Solenoid (CS) conductor. Full scale TF and CS conduits were fabricated using ...carbon-reduced SUS316LN and boron-added (~40 ppm) high manganese stainless steel (0.025C -22Mn -13Cr -9Ni -0.12N: JK2LB), respectively. Welding condition was optimized so that back bead does not interfere a cable insertion. The weld joint samples were compacted by a compaction machine that was newly constructed and tested at 4.2 K. Mechanical characteristics at 4K of CS, TF conduits and CS welded joint satisfied ITER mechanical requirements. TF welded joint shows slightly lower value of 0.2% yield strength (885 MPa) than that of ITER requirement (900 MPa). The TF conduit contains nitrogen content of 0.14%, which is minimum value in ITER specification. The lower nitrogen content may be caused by the release of nitrogen from molten metal during non-filler welding resulting in a 4 K strength decrease. To satisfy the ITER requirements, minimum nitrogen contents of conduit should be increased from 0.14% to 0.15% at least. Therefore, JAEA successfully developed TF and CS conduits with welding technologies and finalized the procurement specification for ITER conductor jacketing.
Abstract In 2023, the manufacturing of all the ITER TF coils has been completed 15 years after the sign of procurement arrangements in 2008. This paper has been jointly submitted by F4E and QST to ...recollect the lessons learnt in the production of the two parties along the last 15 years.
The Japan Atomic Energy Research Institute developed a jacket material called JK2LB (0.03C-22Mn-13Cr-9Ni-1Mo-0.2N-B) for the Central Solenoid (CS) conductor in the International Thermonuclear ...Experimental Reactor (ITER). To demonstrate production feasibility of CS conductor jacket, trial fabrication of a full size jacket using hot extrusion followed by cold drawing of the JK2LB billets was performed. As a result of dimensional measurement, the ITER dimensional requirement for circle-in-square jacket has been achievable. We achieved the requirement of 0.2% yield strength >1000 MPa and K IC (J)ges130 MParadicm for solution treated + aged jacket. It has been observed that applied cold work strongly affects the toughness of jacket before and after aging. We estimate that C and N reduction will be required to achieve the required strength and fracture toughness for ITER CS jacket. The fabrication R&D has prepared us for mass production of jacket for the ITER CS conductor procurement
The material of the TF coil case in the ITER requires to withstand cyclic electromagnetic forces applied up to 3
×
10
4 cycles at 4.2
K. A cryogenic stainless steel, JJ1, is used in high stress ...region of TF coil case. The fatigue characteristics (
S–
N curve) of JJ1 base metal and welded joint at 4.2
K has been measured. The fatigue strength of base metal and welded joint at 3
×
10
4 cycles are measured as 1032 and 848
MPa, respectively. The design
S–
N curve is derived from the measured data taking account of the safety factor of 20 for cycle-to-failure and 2 for fatigue strength, and it indicates that an equivalent alternating stress of the case should be kept less than 516
MPa for the base metal and 424
MPa for the welded joint at 3
×
10
4 cycles. It is demonstrated that the TF coil case has enough margins for the cyclic operation. It is also shown the welded joint should be located in low cyclic stress region because a residual stress affects the fatigue life.
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