Dynamic study of a steam Rankine cycle using CATHARE-3 system thermal-hydraulic code: Application to Superphenix fast reactor

• CATHARE-3 is used for the simulation of a 620 MW Rankine cycle. • An increase of 1 ° C of the cooling water temperature implies a decrease of 1.15 M W of the electrical output. • Regulation-free simulations enable the quantification of the impact of a change in the Rankine cycle on the reactor core. • Implementation of regulations enables the simulation of load following mode. There is a growing interest for innovative power conversion systems for nuclear power plants in the context of the decarbonization of the energy mix. This motivates the need of dynamic models of Rankine cycle to be integrated in conception and safety analysis. In this paper, a simplified version of the steam Rankine cycle of the French sodium-cooled fast reactor Superphenix is modeled using the thermal–hydraulic code CATHARE-3. This completes previous works on the modeling of the primary and secondary circuits of this reactor with CATHARE and enables the simulation of the entire power plant. In the first part, parametric studies of the Rankine cycle enable the computation of the gross efficiency as a function of cooling water temperature and as a function of the power load. In the second part, transient simulations are performed. The regulations of the Rankine cycle are implemented in order to simulate a load following scenario. Then, the Rankine cycle is coupled with the CATHARE-3 models of the primary and the secondary sodium circuits (including the neutron point kinetics model for the core). Free dynamics scenarios are simulated: a step variation of the turbine admission valve and a step variation of the cooling water flow rate.