Nuclear power offers an abundant energy supply for the long term and at reasonable costs. Both are badly needed in this world of limited energy reserves and rising energy prices. On the other hand, there are questions widely discussed in the public on nuclear safety, on acceptable means of nuclear waste disposal, and concern on the proliferation of nuclear weapon capabilities. Public confu- sion is widespread since facts are often overshadowed by emotions. Recognizing the need for reliable, factual and comprehensive information on nuclear energy, this book on Nuclear Fission Reactors is published .to present the scientific and technical facts of nuclear fission reactors, and to analyse their potential role and risks. The author, Professor Dr. G. Kessler, has worked in nuclear research and project management since 1963. From 1975 to 1978, he acted as project leader for the German/Belgian/Dutch Fast Breeder research and. development activi- ties. Since then, he has been Director of the Institute of Neutron Physics and Reactor Technology in the Karlsruhe Nuclear Research Centre. The book is part of the series "Topics in Energy" issued by Springer Publish- ers. The intention of this series of in-depth analyses is to present the facts, inherent problems, trends and prospects of energy demand, resources and tech- nologies. The vital importance of energy for human activities has become apparent to the public particularly through dramatic events in the area of oil supply.