[en] The developments of investigation on novel nuclear thermodynamic cycle systems are summarized. On the basis of energy cascaded utilization theory and high temperature reactor technology. Humid helium turbine closed cycle and helium-steam turbine combined cycle were presented. The efficiency of these systems are 10-30 percents higher than that of conventional nuclear system, and specific power is 2 times higher. At the same time, some related systems were modeled and analyzed and characteristics of them are revealed. These works will present aids to the research and development of new relational power system in this field