Multilayer pebbles for application to new divertor systems

Isobe, Michiro; Matsuhiro, K.; Ohtsuka, Y.; Ueda, Y.; Nishikawa, Masahiro

doi:10.1088/0029-5515/40/3y/327

Cited by 17 publications

(9 citation statements)

References 9 publications

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“…If a pebble flow is selected as the renewable divertor target instead of liquid metal jets, there is no current path along the flow. In past studies, applicability of multilayered ceramic pebbles as the divertor target has been investigated [12,13]. In this study, 100% shielding rate was achieved by the ceramic pebbles with a diameter of 1 mm [12].…”

Section: Introductionmentioning

confidence: 86%

Plasma irradiation experiment on the metal pebble flow in the TPDsheet-U

Ohgo

Goto

Takimoto

et al. 2021

Fusion Engineering and Design

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Section: Introductionmentioning

confidence: 86%

Plasma irradiation experiment on the metal pebble flow in the TPDsheet-U

Ohgo

Goto

Takimoto

et al. 2021

Fusion Engineering and Design

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“…13(9)), screw conveyors for liquid metal (Fig. 13 (10)) and for pebbles (Fig. 13 (11)) are installed.…”

Section: Cardistry-b3mentioning

confidence: 99%

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

Miyazawa¹,

Goto²,

Hamaji³

et al. 2021

Nucl. Fusion

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The cartridge-type blanket for the helical reactor has been updated and named the CARDISTRY-B3. Together with this, the ceramic pebble ergodic limiter/divertor system named the REVOLVER-D3 has been adopted in the design. There was a difficulty in fabricating the blanket cartridges due to the first wall shape with three-dimensional surface. This difficulty has been removed by introducing the slit first wall, where the first wall surface is formed by alternately stacking solid metal plates and porous plates made of metal or ceramic. The liquid metal flowing inside the blanket cartridge oozes out through the porous plates and forms the surface flow covering the first wall. Solid target plates for the helical divertor has been omitted, because the divertor region is already covered and protected by the liquid metal surface flow. The liquid metal freely falls inside the blanket cartridges by the gravity force and then exhausted to the pool set on the lower port. The ceramic pebbles, which are dropped to the inboard-side ergodic layer to form the flowing limiter divertor, also flow into the liquid metal pool. The pebbles and liquid metal are individually elevated again by screw conveyers. Since the free surface of the liquid metal is exposed to the plasma, the vapor pressure of the working liquid metal should be low enough. Ternary or quadruple alloys, which include Li, Sn, Pb (or Bi), and Er, have been selected as the candidates of the functional liquid metal for the CARDISTRY-B3 that satisfies the requirements of low vapor pressure, low density, low melting point, and high tritium breeding ratio. In this study, the coordinated design of CARDISTRY-B3 and REVOLVER-D3 for the FFHR-b3 is presented. The FFHR-b3 is one of the design options that aims at demonstration of 100 MW net electricity with two times larger devise size than LHD.

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“…This is larger than the tolerable heat load of the "state-of-the-art" divertor being developed for ITER [1]. To solve this problem, "renewable" divertor concepts such as the liquid metal divertors and/or limiters [2][3][4][5], pebble divertors [6][7][8], etc., have been investigated. A liquid metal divertor named the REVOLVER-D (Reactor oriented Effectively VOLumetric VERtical Divertor) consisting of molten tin shower jets has been proposed for the helical fusion reactor FFHR [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…In the past pebble divertor design, ceramic pebbles and ferromagnetic pebbles have been adopted. However, the exchange of broken pebbles is necessary [6][7][8]. Here, we propose a new concept of Fusible Metal Pebble Divertor (FMPD) named the REVOLVER-D2, which uses tin pebbles.…”

Section: Introductionmentioning

confidence: 99%

A New Divertor System Using Fusible Metal Pebbles

Ohgo

Goto

Miyazawa

2019

Plasma and Fusion Research

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A fusible metal pebble divertor system named the REVOLVER-D2 is newly proposed here, based on the molten tin jet divertor REVOLVER-D and the pebble divertor concepts. In the REVOLVER-D2, solid tin pebble flows are used as the divertor target. Molten tin pools receive the falling tin pebbles to mitigate the impact of the heavy metal shower. All pebbles are melted in the molten tin pool and recycled into the tin pebbles again. The solid tin pebbles are formed inside the vacuum vessel by the shot tower method using silicone oil pools. This concept enables simultaneous achievement of a high heat load tolerance and a high evacuation efficiency, while mitigating the MHD effects. A high heat load can be removed by the pebble flow if the pebble size is large enough and the velocity is fast enough as with the molten tin jet. Although the charge up of pebbles affects the pebble motion due to the Lorentz force and the Coulomb force, the Lorentz force is negligible if the injection velocity is fast enough. For example, center-to-center pebble distance due to the Coulomb force will be ∼ 4 mm in the case of the injection velocity of 10 m/s if the molten tin pool is placed 2 m under the point where pebbles enter the ergodic layer.

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Multilayer pebbles for application to new divertor systems

Cited by 17 publications

References 9 publications

Plasma irradiation experiment on the metal pebble flow in the TPDsheet-U

Plasma irradiation experiment on the metal pebble flow in the TPDsheet-U

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

A New Divertor System Using Fusible Metal Pebbles

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