Thermal–hydraulic modeling of water/Al₂O₃ nanofluid as the coolant in annular fuels for a typical VVER-1000 core

Highlights: •We present a thermal–hydraulic analysis of nanofluid as the coolant in a typical VVER-1000 reactor. •To validate, the results are compared with visual FORTRAN language, DRAGON/DONJON code and COBRA-EN code and FSAR. •The comparison of the calculated results shows that the results are in good agreement with other studies. •It is explained that by the use of the Al₂O₃ nanoparticles, the central fuel temperature is reduced. •In annular fuel, it is described the peak temperature in the fuel region is decreased. -- Abstract: In this paper, a thermal–hydraulic analysis of nanofluid as the coolant is performed in a typical VVER-1000 reactor with internally and externally cooled annular fuel. The fuel assembly for annular case with 8 × 8 arrays is considered for annular pin configuration. The considered nanofluid is a mixture composed of water and particles of Al₂O₃ with various volume percentages. The fuel rod is modeled using a CFD code. To validate the calculated results, the present results of solid fuel with nanofluid and pure water are compared with other studies which have been done with visual FORTRAN language, DRAGON/DONJON code, COBRA-EN code and the mentioned analytical approaches have been validated by comparing with the final safety analysis report (FSAR). The comparison of the calculated results shows that the results are in good agreement with other studies. Thus, the accuracy of the validation is satisfactory. Moreover, the temperature distributions of the fuel, clad and coolant are described for water/Al₂O₃ nanofluid in solid fuel and annular fuel. It is observed that as the concentration of Al₂O₃ nanoparticles increases, due to higher heat transfer coefficient of Al₂O₃ nanofluid, the temperature of the coolant is increased and the central fuel temperature is reduced. Thus, it improves margin from peak fuel temperature to melting. Finally, it is illustrated the use of the annular fuel instead of solid fuel in core of the reactor, security and efficiency of the nuclear power plant will be increased.