Eutectic Lead–Bismuth Alloy as a Possible Coolant in the Fusion Reactor Cooling System

In the design of the DEMO fusion reactor, as well as the facility of a fusion neutron source FNS, as one of the options, it is assumed that a three-loop cooling system will use a blanket of liquid metals. Liquid lithium from the primary loop transfers heat in intermediate heat exchangers to liquid sodium of the second loop, which in turn transfers heat to the water of the third loop in the steam generator. The possibility is considered of using a “neutral” coolant in the second loop—a eutectic lead–bismuth alloy, which does not chemically interact with either liquid lithium or water in the third loop, which makes it possible to exclude contact of liquid lithium or sodium with water. A preliminary calculation of the intermediate liquid lithium–eutectic alloy heat exchanger has been performed, and it is shown that the use of this alloy will allow for the cooling of the fusion reactor with the same number of intermediate heat exchangers and without a significant increase in their size.