CONICET | Buscador de Institutos y Recursos Humanos

Abstract. A steady state CFD simulation of the moderator tank of Atucha II Nuclear PowerPlant (a Pressurized Heavy Water Reactor PHWR) was performed. Three-dimensional (3D)detailed modeling of the tank was achieved including inlet and outlet ring-shapeddistributors, the coolant channel (CC) tubes and the control and safety rod guide tubes. Twoheat sources were taken into account: the conduction/convection from the coolant channels?fluid and the heat transfer by thermal neutron moderation. For the former, suitableboundary conditions (wall temperature) at the CC tube walls were arisen from 2Destimation of the conduction/convection heat through the coolant walls. The coolanttemperature profile along each CC (obtained from a previous 1/3D model) along withcorrelations for the in-channel side convective coefficient were considered. The effectiveconduction coefficient was estimated by fitting the overall expected transfer power. For thelatter, a homogeneoussource was implemented.Simulations allowed a thorough understanding of the complex flow and the heat transferphenomena, while acquiring useful information about the temperature distribution in themoderator. The most relevant conclusion is that the power transferred from the CCs to themoderator does not show linear dependence on the fission power but on the coolanttemperature, which is very similar for all CCs. These results become of prime importancewhen defining more accurate boundary conditions for modeling the in-channel flow with apreviously developed, in-house, 1/3D multidimensional model of the reactor pressurevessel (RPV). The 3D model developed is the starting point to carry on unsteadysimulations in the moderator tank,such as reactor Safety Control Rod Axe Man (SCRAM),heat removal during a primary pump shut down or boron distribution during a fast shutdown injection.

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