J.O.Denschlag
Institut f r Kernchemie, Universit t Mainz, D-55128 Mainz, Germany
The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor ?, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (PWR, BWR, RBMK, FBR). The new concept of the Accelerator Driven Systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.
The impact of nuclear fission on the human way of life is due to the fact that the fission process can be organized in such a way that a self-propagating chain reaction proceeds. This is because the one neutron normally required to induce a fission reaction in a nucleus, like 235U or 239Pu, sets free 2 to 3 neutrons that can induce new fission reactions (see Chapter4...
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