Fast Breeder Test Reactor(FBTR) is in operation since 1985. Tests and analysis have been performed to assess the conduciveness of the layout to natural convection under loss of pumping flow conditions. One such test refers to the secondary sodium circuit, which forms the link between the heat source (Core) in the primary sodium system and the steam generator which is the final heat sink. This paper details out the tests and two one dimensional numerical models for assessing the flow and compares the predictions with actual test results. Though there is a reasonable match, better assessment is possible with multidimensional models to predict the flow stagnation regions.

Key Words: Fast Reactor, Sodium, Intermediate Heat Exchanger, Piping, Natural convection, Test, Numerical model.