Modern power sources including nuclear one are characterized. Basic information on radiation protection of man and biosphere is presented. Problems of radiation effect of nuclear fuel cycle enterprises on population and environment are discussed. Comparative evaluation of nuclear and thermal power effect on biosphere is made. It is shown that nuclear power is the safest power source at the present development state. The conclusion is drawn that the use of nuclear energy controlled and limited by scientifically founded norms does not present radiation hazard for population and environment.