Numerical simulation of transient forced and mixed convection sodium flow experiments

Abstract

Sodium-cooled fast-neutron reactors are currently considered to be the most mature type of reactor able to closing the fuel cycle in the context of generation IV reactors. In a sodium-cooled pool-type reactor, thermal stratification can occur in the pools in several cases. This phenomenon is monitored closely because it can impact the behavior of the reactor and might lead to thermal fatigue.

In the 1980s, the SUPERCAVNA test facility was built and operated at the CEA Grenoble research center. The experimental campaigns investigated the onset of thermal stratification in a rectangular pool. During transient tests, cold sodium was injected in a hot sodium pool. Depending on the inlet flow velocity, thermal stratification would form and erode the hot sodium layer in the pool. In other cases, no thermal stratification was formed and efficient mixing occurred. The data from these tests constitute a set of CFD-grade experiment that are very useful to assess the capability of CFD codes to capture the onset of thermal stratification. Code_Saturne was selected to perform calculations of three transient tests from the SUPERCAVNA experimental campaign. Two tests were well captured. A mixed convection test proved more difficult to predict and lead to extensive tests of turbulence and turbulent heat flux models.

In this paper the SUPERCAVNA facility and the tests of interest are presented. Then, the CFD model of the facility is described and the results are presented and discussed. Conclusions and recommendations for this type of flows are proposed.