The UNICO multi-physics code to analyze transients in sodium fast reactors

UDC: 
УДК: 621.039.51

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Abstract: 

The Russian multi-physics code UNICO is designed to analyze in detail the temperature and velocity fields in the fast reactor core, under transient conditions. The code is meant to make 3D coupled computation of neutronic, thermal-hydraulic and thermal-mechanic characteristics accurate to each separate core fuel assembly (FA). A core thermal hydraulic model is a set of fuel assemblies installed into an inter-wrapper space. Sodium thermal hydraulics in the core inter-wrapper space is calculated in 3D approximation and the relevant equation system is solved in the triangular computational mesh. Sodium velocity and temperature distribution are taken into account inside each fuel assembly. A 3D FA model is used to calculate the temperature of fuel and steel cladding. Based on the information about the temperature of fuel, fuel element cladding and FA wrappers the core deformation behaviour is analyzed and then the respective changes in neutronic characteristics are calculated. The results of test calculations are given; they confirm the fact that insufficiently correct consideration of spatial distribution of thermal hydraulic parameters in the reactor core can cause appreciable errors (uncertainties).

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