Energy-Resources - the Safety of Fusion-Reactors

In part I the world's present energy production and consumption will be treated, as well as the expected increase in demand in the next decades. The limited availability of fossil fuels, the impact on the environment caused by the burning of these fuels, the restricted applicability of renewable energy sources, and the possible dangers connected with energy production by means of nuclear fission are all factors urging us to consider alternative approaches. The most promising future energy production method is based on controlled thermonuclear fusion. At present, feasible fusion reactors are expected to burn deuterium-tritium mixtures. One component of the fuel, deuterium, is abundantly available in the world. The other component, tritium, does not occur in nature and has to be bred, e.g. from lithium. The most obvious advantage of fusion reactors is the virtual inexhaustibility of the fuel. In part II some aspects of future fusion reactors will be treated. A major advantage of such reactors will be their inherent safety and low energy content. On the other hand, we may encounter a number of safety problems. The yield of energetic neutrons will be high. The neutrons have to be moderated in order to utilize their thermal energy. Furthermore, the moderated neutrons will be used to breed one component of the fuel: tritium. Since tritium is a radioactive isotope it has to be handled with the greatest care. Although no radioactive waste is produced in thermonuclear reactions, the high neutron flux in the system may cause induced radioactivity in structural materials. Radioactive waste problems after close-down of a reactor may be reduced by a proper choice of materials, e.g. new metal alloys. Extensive shielding of the reactor is of primary importance to protect the apparatus and the environment from dangerous neutron irradiation.