Application of lead and lead-bismuth in the heat-removal systems of tokamak reactors

Abstract

The salient features of the use of lead and lead-bismuth in the power-generating loops removing heat from the blanket of a tokamak reactor are set forth. The results of experimental and theoretical investigations and analysis in substantiation of the use of heavy liquid-metal coolants in systems converting the energy of a blanket in a tokamak reactor into electricity are presented.One of the main requirements of nuclear power -inherent safety of reactors -is initiating studies of heavy liquidmetal coolants as alternatives to sodium coolant, which has been mastered and has better thermophysical characteristics and other advantages. This requirement also makes it useful to study them as alternatives to lithium in the energy conversion systems of thermonuclear reactors, specifically, in the blanket of a tokamak reactor.Characteristics of Lithium, Lead, Lead-Bismuth as the Coolant for a Tokamak Reactor. The thermophysical properties of lithium as a coolant (heat capacity, thermal conductivity, density) are undoubtedly better than those of lead and lead-bismuth: lithium is less corrosive, and experience in using lithium in research and semicommercial stands and setups has been accumulated in this country and abroad. A serious drawback of lithium as a coolant is that it presents a fire hazard. Fire safety in loops and systems with lithium, just as with sodium, can be achieved by augmenting with complicated engineering safety systems and with protection and containment systems and by decreasing the cost-effectiveness of the setup. When lead and lead-bismuth come into contact with air the free surface gradually oxidizes, and when a continuous layer of slag remains on the surface of the liquid metal oxidation slows down.The interaction of lithium with water, a steam-water mixture, and steam with formation of a corrosive alkali and explosion-dangerous hydrogen, just as with the use of sodium, requires an additional intermediate loop using water as the working body of the Rankine cycle for converting heat into electricity. When the blanket is cooled by lithium, using carbon dioxide gas as the working body and the Brayton cycle also requires an intermediate high-temperature loop because of the formation of lithium carbides during a possible accident with an interloop leak in the heat exchangers. The use of lead or lead-bismuth makes it possible to use in such cases simpler and more cost-effective two-loop schemes, which makes the setup as a whole safer.In designs of thermonuclear reactors, as a rule, breeding of tritium occurs as a result of reactions of neutrons with lithium nuclei. This is possible if liquid lithium is used as the coolant. However, the operation, repair, and decommissioning of a branched, complicated, power-generating, lithium cooling loop, containing, aside from conventional radionuclides, the biologically dangerous volatile substance tritium are complex and dangerous. The well-known technological process for pro-

Simulation and Modeling of Optical Properties of U, Th, Pb, and Co Nanoparticles of Interest to Nuclear Security Using Finite Element Analysis

“…For instance, uranium dioxide (UO 2 ) is the principal fuel in most significant commercial light-water nuclear power reactors [ 1 , 2 , 3 ]. Moreover, lead is extensively used in fission reactors as a substitute for sodium, and in the blanket of fusion reactors as a substitute for lithium [ 4 ]. Additionally, thorium is used in various nuclear reactors, including light-water, fast spectrum sodium, molten salt, and high-temperature gas-cooled, as well as in fission-fusion hybrid systems and advanced accelerator-driven systems [ 5 , 6 , 7 ].…”