Investigation of hybrid nanofluids effects on heat transfer characteristics in WER-1000 nuclear reactor

摘要

In this study, the analysis of heat transfer characteristics of VVER-1000 nuclear reactor by using hybrid nanofluids as a coolants in subchannels in hot fuel assembly have been performed. Firstly, the criticality (k_(eff)) and fuel assembly power distributions of the WER-1000 reactor by using Monte Carlo particle transport (MCNP) code to determine of the heat transfer characteristics with COBRA Ⅳ PC code have been examined. Secondly, the axial coolant temperature distributions and Departure from Nucleate Boiling Ratio (DNBR) values in hottest channel for Cu, CuO and TiO_2 nanoparticles of the different volume fractions (0.05, 0.01 and 0.1) mixed with 0.1 vol Al_2O_3 hybrid nanofluids have been analyzed. The obtained results by using hybrid nanofluids have been compared with the pure water results. The k_(eff) decreases with the increase of volumetric fractions of hybrid nanoparticles Cu, CuO and TiO_2 mixed with 0.1 Al_2O_3 in the coolant. The maximum temperature has been reached by the pure water coolant at the end of the channel as 612.68 K whereas, the highest temperature change has been obtained in the case of 0.1 Al_2O_3 + 0.1 TiO_2 as 617.35 K when evaluated among nanoparticle themselves. The results of analysis show that the heat transfer enhances with increasing hybrid nanoparticles volume fractions in the subchannel geometry. Also, the obtained minimum DNBR values using hybrid nanofluid haven't been exceed the safe operational limits; therefore the reactor operation would be safer.