Preliminary CFD Analysis of Innovative Decay Heat Removal System for the European Sodium Fast Reactor Concept

A major safety design objective for sodium cooled fast reactors is the practical elimination of the prolonged failure of the decay heat removal function. In order to achieve this objective, innovative decay heat removal system concepts are being developed. This paper discusses the preliminary CFD analysis of the design of an Innovative decay heat removal system implemented in the reactor pit which replaces the safety vessel of the European Sodium Fast Reactor. The efficiency of the oil cooling system is evaluated. A representative part of the reactor pit structure is modelled. The heat path is from the reactor vessel wall through a gap, an insulation layer into a concrete structure. The heat sinks are the oil cooling system and the ambient. A simplified case is used for verification with an analytical solution. It is shown that the oil cooling system is capable to remove the heat from the structure and keep the temperature there below 70 degrees Celsius. At nominal conditions about 3 MW have to be removed and at a top oil cooling temperature of approximately 200 degrees.