Concept of magnet systems for LHD-type reactor

Feasibility studies on applying high-temperature superconductors (HTS) to the LHD-type heliotron fusion energy reactor FFHR are being carried out. Because the HTS conductor has high cryogenic stability at elevated temperature operations (e.g. 20 K) and the refrigeration power has enough margins, it is considered that Joule heating dissipation generated at joints of conductors is acceptable to facilitate the segmented fabrication of the helical coils of FFHR. In this study, the joint resistance with 10-kA class YBCO conductors has been measured to evaluate the joule heating dissipation in the FFHR magnet. The experiment has been carried out by fabricating a soldered lap joint and a mechanical lap joint. The feasibility of segmented fabrication is examined by the measured results.

Section: Introductionmentioning

confidence: 99%

Measurement of the Joint Resistance of Large-Current YBCO Conductors

Terazaki

Yanagi

Tomida

et al. 2012

“…The present design, FFHR-d1, is equipped with a pair of continuously wound helical coils, having a major radius of 15.6 m, a minor radius of 3.744 m and a helical pitch number of 10, that produce a 4.7 T toroidal magnetic field to generate 3 GW of fusion power [13]. The stored magnetic energy is 160 GJ and a 100-kA conductor is required to be used at the maximum magnetic field of ∼12 T. The primary selection for the helical windings is a CIC conductor using Nb 3 Al strands [14], which is regarded as an extension of the ITER technology. However, considering the difficulties related to CIC conductors, such as the complicated plumbing required and the degradation of the critical current due to strain, an indirectly-cooled LTS conductor using Nb 3 Sn strands and an aluminum-alloy jacket has also been considered [15].…”

Section: Design Of a 100-ka-class Hts Conductor For DC Magnets Of Fusmentioning

confidence: 99%

“…The winding pack consists of 390 turns of HTS conductors, each with an operation current of 94 kA, installed in a stainless-steel "internal plate" with circular grooves. This is the same concept employed for the CIC conductor version of the FFHR helical coils [14]. The internal plate is the layer winding version of the "radial plate" used in the ITER TF coils with pancake winding.…”

Section: Design Of a 100-ka-class Hts Conductor For DC Magnets Of Fusmentioning

confidence: 99%

Feasibility of HTS Magnet Option for Fusion Reactors

Yanagi

Terazaki

Natsume

et al. 2014

Conceptual design studies are being carried out on the application of high-temperature superconducting (HTS) conductors and coils to the magnet systems of fusion reactors. A 100-kA-class HTS conductor is required to be applied at high magnetic fields of > 12 T. A simple stack of YBCO tapes embedded in copper and stainless-steel jackets is found to be a practical approach to producing large-scale conductors that exhibit high cryogenic stability and mechanical rigidity. The feasibility of the segmented fabrication method for large complex HTS coils, such as the helical coils in the LHD-type helical fusion reactor FFHR-d1, is being investigated by developing mechanical bridge-type lap joint technology of HTS conductors.

“…A stored magnetic energy W mag is an index of the total mass amount of the superconducting magnet system including the supporting structure. The superconducting magnet system with W mag = 120-140 GJ can be constructed with a small extension of the ITER-relevant technology [4] and the achievable maximum value is estimated to be ∼160 GJ. Therefore, W mag ≤ 160 GJ is assumed in the design of FFHR-2m2.…”

Section: Design Window Of a Lhd-type Heliotron Reactormentioning

confidence: 99%

A Robust Design Window for the Heliotron DEMO Reactors

Goto

Miyazawa

Tanaka

et al. 2011

According to the achievements in the Large Helical Device (LHD) experiments, a design of a DEMO reactor with a LHD-type heliotron system is foreseeable. On the other hand, a DEMO is the next step reactor and high reliability and feasibility are demanded in its design. In this study, a robust design window, i.e., the design window that is not sensitive to a change in uncertain physics parameters, was surveyed through parametric scans using a system design code. It was found that a difference in main design parameters (major radius, magnetic field strength, fusion output) gives only a small change in a dependence of physics requirements on the physics conditions. Therefore, it is important to find the design window with a lower requirement on the confinement improvement to assure the design robustness. In this respect, a reduction in the minimum inboard blanket space, one of the key parameters in a LHD-type heliotron reactor design, can effectively expand the design window and contributes to the design robustness. An acceptance of higher neutron wall load and an achievement of further high confinement improvement are also expected to make both a DEMO and a commercial reactor to be more feasible and economically attractive.