Progress of the Design of HTS Magnet Option and R&D Activities for the Helical Fusion Reactor

Performance of a Mechanical Bridge Joint for 30-kA-Class High-Temperature Superconducting Conductors

“…According to [11], forty (twenty layers and two rows) 15-mm-wide REBCO tapes are needed to transport 94 kA at 20 K and 12 T in the FFHR-d1 helical coil windings. If we set the length of one step of the bridge joint to 38 mm (i.e., the total length of one bridge joint is about 1.5 m), the actual contact length of each step will be 30 mm if we use the geometry of sample B.…”

“…Tohoku University and NIFS have collaboratively studied the REBCO conductor and its joining technique for the FFHR-d1 [10], [11]. In 2012 and 2013, we began by fabricating and testing 30-kAclass Gadolinium Barium Copper Oxide HTS (GdBCO) conductors with joint sections fabricated with mechanical bridge joints.…”

Novel divertor design to mitigate neutron irradiation in the helical reactor FFHR-d1

“…Because of the cyclic symmetry, only a 36 • region of the structure was needed for the analytic model. In this analysis, the superconductor was assumed to be made of a high-temperature superconducting (HTS) conductor using a rare-earth barium copper oxide (REBCO) tape [10,11]. The equivalent physical properties of the HC and VFC winding sections were calculated by a homogenization analysis using the geometry of the cross section and physical properties of the constituent materials [11].…”

Conceptual design of a compact helical fusion reactor FFHR-c1 for the early demonstration of year-long electric power generation

“…The achievable fusion gain is ~10 when the operation regime is restricted by the physics parameters that have already been confirmed by the LHD experiment, even if a high-field option with the magnetic field on the centre of the helical coil winding, B c ~ 6 T, is adopted. In the meantime, several innovative ideas have been proposed, for example, the 'joint-winding' method of helical coils using the high temperature superconductor (HTS) to shorten the time for the winding [3], blanket space enlargement (~15%) by placing supplementary helical coils (NITA coils) to secure the tritium breeding and neutron shielding performance [4], adoption of a liquid metal ergodic limiter/ divertor system to enable high heat/particle load accommodation (>100 MW m −2 ) and easy maintenance [5], and proposal of cartridge-type blanket modules to achieve construction and maintenance without complicated works inside the vacuum vessel [6]. Although these innovative concepts have been proposed to overcome the engineering difficulties in the design of FFHR-d1, these concepts also enable a compact reactor design if focusing on the production of positive net electric power (P e,net > 0) by allowing operation with auxiliary heating and a shorter reactor lifetime due to the higher neutron flux to the superconducting coils.…”