Novel features of the helical volumetric neutron source FFHR-b2

Abstract

The compact helical fusion reactor FFHR-b2 is a multipurpose HElical Volumetric Neutron Source (HEVNS) available as the component test facility to test the divertor and blanket systems. In the latest design, three new technologies of the HTS (High-Temperature Superconducting) conductor, the ceramic pebble divertor, and the cartridge-type blanket are adopted. Tin-based functional liquid metals (FLMs) including lithium are considered as the working fluid for the blanket. The FLMs have multi functions of low vapor pressure, low density, low melting point, low corrosiveness, high tritium breeding ratio, and so on. The target construction cost of the FFHR-b2 has been set to 200 billion JPY. The main target of FFHR-b2 is to demonstrate the fusion gain larger than one. To achieve this in a relatively small device, the tangential Neutral Beam Injection (NBI) heating with a moderate energy of 80 keV is adopted for the FFHR-b2. The beam-plasma fusion with 5 MW of NBI heating can produce a fusion power of 5 MW that is larger than the absorbed power of 3 MW.

Bubbling phenomenon of liquidized Sn–Bi–Li–Er alloy under hydrogen plasma exposure

“…By increasing the sample temperature above the melting point, SBLE is liquidized. Thermodynamical calculation of SBLE has been performed by Miyazawa et al 23) In the case of an SBLE used in this study (Sn: 42.1%, Bi: 30.8%, Li: 24.9%, Er: 2.2%), solidus temperature and melting point are ∼135 °C and ∼600 °C, respectively. Hence, between 135 °C and 600 °C, SBLE shows metallic liquid behavior.…”

“…Miyazawa has reported that the stirring procedure of heated SBLE in a hydrogen gas environment is required to obtain a clean metallic liquid surface. 23) According to this report, SBLE is heated at a temperature of 350 °C and is exposed to hydrogen gas at a pressure of 9.5 Pa. At heated condition, the sample pieces melt and get together into one liquid piece with a graycolored surface. In this situation, the sample surface becomes smooth with a certain surface curvature.…”

“…SBLE is mainly composed of Sn-Bi, which has a low melting point and is admixed with Li and Er; those are used for tritium breeder and stainless steel corrosion suppressor, respectively. 22) Furthermore, the use of the SBLE for a new concept blanket has recently been proposed. In the conventional concept of the blanket system, LM flows through tubes and is separated from the plasma with a solid metal wall.…”

“…In the conventional concept of the blanket system, LM flows through tubes and is separated from the plasma with a solid metal wall. By contrast, a cartridge blanket system called CARDISTRY-B3 23) is proposed. In this new concept, functional LM (FLM) flows on the first wall surface and is directly exposed to fusion plasma.…”

Coordinated design of the cartridge-type blanket and the ceramic pebble divertor for the helical reactor FFHR-b3

“…In this paper, improved designs of pebble divertor and cartridge-type blanket are described. The design target is set on the FFHR-b3, which is recently defined by taking the confinement enhancement due to the magnetic configuration optimization into account [23]. The device parameters of the FFHR-b3 is given in the next section.…”