Our purpose in this paper is to describe the most expedient strategic line of nuclear power engineering development based of fission and fusion reactors that will ensure the electricity generation in the predetermined scale, solve fuel problem for long-term outlook and secure the lowest risk of environmental radioactive contamination. Practical realization of modern ideas of the thermal reactors replacement by fast ones is unlikely because of process duration and necessity of additional uranium resources. In addition a fuel cycle of fast reactors will require quick reprocessing of high-active spent fuel resulting in high risk of negative radioactive impact on environment. Replacement of the thermal reactors by the fast ones would result in the full change of constructional and operational infrastructure. In case of nuclear power engineering development integrating fusion and fission reactors, natural uranium demand will correspond with current estimations for affordable resources. Risk of radioactive contamination from spent fuel reprocessing will be the lowest and present nuclear energy infrastructure will be kept alive, since thermal reactors will be prevalent. Thus, integration of fusion and fission nuclear reactors gives significant synergetic effect, where deficiencies of each technology are compensated by the abilities of another nuclear energy production technique.