Neutronic and Thermalhydraulic Evaluation of Annular Fuel in PWR with Three Different Nanofluids

Abstract

In pressurized nuclear reactors, one of the fuel design principles is the fuel centerline temperature limit. Since the thermal conductivity of UO2 is not high, the temperature increases rapidly from the fuel surface to the fuel center. To overcome this limitation, the use of annular type fuels instead of solid fuels is one of the improvement efforts. In this study, the effects of using annular fuel in a typical PWR are investigated. At the same time, the effects of adding nanoparticles (𝐴𝑙2𝑂3, 𝐶𝑢 and 𝑇𝑖𝑂2-with volume fractions of 0 < 𝜑 < 0.2 for neutronic and 0 < 𝜑 < 0.03 for thermalhydraulic calculations) and to the coolant water in the case of solid and annular fuels are also investigated. For both cases, neutronic and thermalhydraulic calculations are made and compared. In neutronic point of view, it has been shown that the use of annular fuel does not cause a significant change in the 𝑘𝑒𝑓𝑓 value but the presence of nanoparticles reduces the 𝑘𝑒𝑓𝑓. This reduction is maximum for Cu+water and minimum for 𝐴𝑙2𝑂3+water nanofluids. In thermalhydraulic point of view, it has been shown that the annular fuel positively affects the fuel temperature limits and the addition of nanoparticles could provide an additional contribution to this, provided that it is in very small amounts (𝜑 < 0.01). Among the three nanoparticles examined, Cu+water is found to be the least suitable both in terms of neutronics and termalhydraulic considerations. 𝑇𝑖𝑂2+water and 𝐴𝑙2𝑂3+water are comparable. It has also been shown that the optimum value for the annular fuel inner radius is approximately 0.4 cm.