Improved structure and long-life blanket concepts for heliotron reactors

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.

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

“…A magnet system of an LHD-type reactor consists of a pair of continuous helical coils and more than one pair of poloidal coils [4]. The position of the poloidal coils is determined by the dipole magnetic field, the quadruple magnetic field, stray field, position of ports, etc.…”

Section: Magnet Systems Of An Lhd-type Reactormentioning

confidence: 99%

Conceptual Design of Magnets with CIC Conductors for LHD-type Reactors FFHR2m

Imagawa

Sagara

Kozaki

2008

LHD-type reactors have attractive features for fusion power plants, such as no requirement of a current drive and a wide space between the helical coils for the maintenance of in-vessel components. One disadvantage was considered the requirment of a large major radius to attain the self-ignition condition with a sufficient space for blankets. According to the recent reactor studies based on experimental results in LHD, the major radius of plasma is set at 14 to 17 m with the central toroidal field of 6 to 4 T. The stored magnetic energy is estimated at 120 to 130 GJ. Both the major radius and the magnetic energy are about three times as large as those for ITER. We intend to summarize the requirements for superconducting magnets of the LHD-type reactors and propose a conceptual design of the magnets with cable-in-conduit (CIC) conductors based on the technology for ITER.

“…Several design options of FFHR have been proposed [2] and among them, the recent design FFHR2m1 has a plasma major radius of 14 m, toroidal field of 6.18 T, maximum field at the conductor of 13 T, and fusion power of 1.9 GW. FFHR-2m1 consists of a pair of helical coils and two pairs of poloidal field coils.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Superconducting Coil Option for the LHD-Type Fusion Energy Reactor FFHR

Bansal

Yanagi

Hemmi

et al. 2008

Large-current-capacity high-temperature superconducting (HTS) conductors using YBCO tapes are being considered as an option for the LHD-type fusion energy reactor FFHR. The typical operating current, magnetic field, and temperature of such conductors in FFHR are 100 kA, 13 T, and 20 K, respectively. A preliminary design of the HTS conductor has been proposed for the FFHR helical coils. Analyses have been performed on the proposed HTS conductor regarding thermal properties, mechanical structures, AC losses, and quench detection and protection. It is suggested that stainless steel might be a better choice for the outer jacket of the HTS conductor compared to aluminum alloy. Due to increased specific heats of conductor materials at 20 K, HTS magnets are supposed to be operated more stably compared to low-temperature superconducting (LTS) magnets operated at ∼4 K. The required refrigeration power is also reduced. Therefore, using HTS conductors, it is considered to be viable to assemble the continuous helical coils in segments with joints of conductors, as additional heat generation at the joints can be taken care by utilizing the surplus refrigeration power. According to these analyses, HTS conductors seem to be promising for the FFHR coils.