The magnetic field effect on heat-exchange characteristics and MHD resistance of lead-bismuth eutectic flow in the TOKAMAK blanket heat-sink systems

A. V. Beznosov, - O. O. Novozhilova, - S. Yu. Savinov, - M. V. Yarmonov, - R. E. Alekseev

State Technical University of Nizhny Novgorod, Nizhny Novgorod, Russia

Abstract
One of the key problems in creation of a thermonuclear reactor (TNR) is to make a rational choice of a coolant for the heat-sink systems of the tokamak blanket and divertor. Lithium is chosen traditionally. Such heavy liquid metals as lead, gallium, as well as lead-bismuth and lead-lithium eutectics, are promising coolants, primarily, for safety reasons. In the TNR heat-sink systems, the coolant moves in a high-power magnetic field that is necessary for plasma confinement. The presence of a magnetic field, when liquid metal coolants are used, results in a significant change in characteristics of the hydraulic resistance and heat exchange between the coolant flow and the heat-exchange surface of the equipment. To reduce the magnetic field effect on the liquid metal flow (to decrease the MHD resistance), electrical insulation coatings (EIC) with a high electrical resistance should be formed on the metal channel surfaces confining the liquid metal flow. The authors have performed a comprehensive study of the creation technologies and characteristics of such coatings. In the systems with heavy liquid metal coolants (HLMC), this role is played by oxide coatings on the channel walls, which are formed by treating the coolant with oxygen and its compounds. An increase in oxygen content in the coolant and the EIC characteristics defined by this content reduce the MHD resistance and improve the corrosion stability of materials for the HLMC flow in the magnetic field. At the same time, the formation of EIC impairs the heat-exchange characteristics, hence, increasing the thermal resistance between the flow core and the heat-exchange wall element. Therefore, experiments are needed, in which the heat-exchange characteristics and the MHD resistance of the HLMC flow are studied simultaneously. It is necessary to develop (refine) the calculation procedures and derive formulas for the heat exchange and hydraulic resistance of the channels in the HLMC systems operated in a transverse magnetic field, with the controllable and regulated content of oxygen. The characteristics of the oxide EIC should be examined and the optimal oxygen content in HLMC should be determined for a tradeoff between hydrodynamics and heat exchange to choose and work out heat exchange concepts for the TNR of tokamak type. Figs 12.