When nanofluids are used as reactor coolants, they provide more effective heat transfer with their increase in thermal conduction properties. This plays an important role in energy production by increasing the efficiency of nuclear reactors. The present study delves into the thermal-hydraulic ramifications of utilizing nanofluids as coolants in the VVER-1000 nuclear reactor. Specifically, the thermal-hydraulic characteristics, encompassing parameters such as coolant temperature and departure from nucleate boiling ratio, were scrutinized in light of the incorporation of magnesium oxide (MgO) and zinc oxide nanoparticles. While performing these analyses, not only uranium but also thorium was used in the core as reactor fuel. Considering the emergence of thorium as a potential fuel material in nuclear technology, its inclusion in the fuel composition contributed to the originality of the research. With the addition of 0.2% MgO nanoparticles to a VVER nuclear reactor using 5% thorium dioxide (ThO2) fuel, the coolant temperature as a result of the channel flow was determined as 617.4 K (while 613.7 K for the light water). When employing thorium fuel (with an equivalent nanoparticle concentration), the maximum temperature exhibited an approximate increase of 3 deg compared to uranium fuel. With the addition of 0.2% MgO nanoparticles, the enthalpy value at the end of the channel was 1303.6 kJ/kg when using 5% ThO2 fuel, while the enthalpy value was determined as 1295 kJ/kg in 3.7% enriched UO2 fuel. As one of the most important results of the analysis, it was observed that the temperature value of the coolant increased when nanoparticles were used.