Chemical Aspects of Fusion Technology

Abstract

Managing thermally controlled nuclear fusion will certainly be regarded one day as one of the most successful accomplishments in nuclear physics. At the same time, however, it will represent a technical achievement unparalleled in the history of science and engineering. This in turn would mean, in retrospect, that decisive contributions had to come from a number of disciplines as diverse as materials and engineering sciences and classical chemistry, and that the same collaboration will have to continue in the future in order to reach the ultimate goal, to construct a reactor capable of producing energy from almost inexhaustible source materials (fuels), such as deuterium and lithium. What is the chemist's role in this development? Similarly as in the development of fission reactors, i.e., the nuclear power plants currently in operation, chemists will have to ensure the existence of a reliable fuel cycle-starting from the availability, storage and reprocessing of the fuel through to the provision for safe storage of the waste. In this review article an attempt will be made to outline the problems associated with these tasks and the approaches to be made by the chemist in solving them. How Does a Fusion Reactor Work?The underlying principle of nuclear fusion is that atomic nuclei are brought together close enough to fuse despite the repelling electric forces of their two identical charges. In D-T fusion, i.e., the fusion reaction at present standing the best chance of technical realization, this process requires deuterons and tritons with a mean thermal energy of about 10 keV. Consequently, a temperature of ca. I00 million K must be produced in the fuel mixture (plasma) of such a fusion reactor. Fusion of a deuterium nucleus and a tritium nucleus leads to the production of a He-4 nucleus (a-particle) and a high-energy neutron (14.1 MeV).The neutron, which carries some 80% of the energy released in the reaction, leaves the plasma without undergoing any major interactions, penetrates the first wall of the reactor, transfers its energy by collisions in the blanket, and produces the tritium necessary to maintain the fuel cycle (Fig. '1) in nuclear reactions with the Li-bearing breeding material in the blanket. This means that 80% of the energy produced in the fusion process is no longer available to maintain the temperature required in the plasma. Consequently, it is imperative that the remaining 20% available