This chapter presents a new design that unites the favorable technical and ecological characteristics of the solar and nuclear power plants. The current designs of nuclear reactors promise integral configuration of the primary coolant loop, secondary coolant loop, and a number of passive safety functions and overall simplification of the reactor. The present nuclear reactor design emphasizes on the safety of the reactor core at all times, i.e., controlling the reactor, cooling the reactor core, and maintaining containment. In case of non-availability of standby emergency DGs during beyond design basis event like Fukushima incident, etc., leading to extended station blackout conditions, the passive decay heat removal system will be affected. Hence, additional DGs have been made as a mandatory requirement in nuclear power plants. In case the ADG could not be mobilized during BDBE, an additional backup power source not affected by BDBE is appreciated. Hence in addition to the diesel power sources (EDG and ADG), a new design was developed for integration of diesel power with solar power. The hybrid system was designed to improve the reliability and availability of passive heat removal system, to ensure a reliable supply without interruption, and to improve the overall system reliability (by the integration with the battery bank). This hybrid power also gives the redundant power supply to the safety critical systems. This chapter also features a detailed reliability analysis carried out for power supplies to the safety critical loads. In addition a comparison was made between PV/diesel/battery with diesel/battery. These new hybrid systems conserves diesel fuel and reduce CO2 as well as particulate emissions that are harmful to environment health. Integration of solar power to the existing battery power will increase the reliability and extended availability of the system and thereby ensures safety of the plant during crisis/calamities.