CATHARE 2 code validation on HE-FUS3 loop

Abstract This paper is part of the validation process of the system code, CATHARE 2, applied to Gas Cooled Reactor studies. In the frame of the European Integrated Project RAPHAEL (ReActor for Process heat, Hydrogen And ELectricity generation) a benchmark exercise on the experimental transients conducted in the HE-FUS3 helium facility (Brasimone, Italy) was organized to assess the codes capability in simulating the thermal–hydraulic and dynamic behavior of Very High Temperature Reactors (VHTR). HE-FUS3 loop contains a wide range of components characteristic of a VHTR like compressor, pipes, diffusers, valves, heaters and heat exchangers. Even if the loop characteristics/configuration is not prototypical of a VHTR design, the loop is operating with helium, the design pressure and temperature set respectively at 10.5 MPa and 530 °C. Experimental data for several steady tests and for two transients corresponding to Loss of Flow Accidents were available. This paper includes first a brief description of the CATHARE 2 code applied to Gas Cooled Reactors. Then a description of the CATHARE 2 modeling for each of the relevant components of the HE-FUS3 loop is given. CATHARE 2 calculations results are then compared and analyzed on the basis of the experimental data. Sensitivity calculations to the modeling and to some input parameters are performed and also described in this report. Taking into account the noted experimental uncertainties of some circuit data, the CATHARE 2 results are in a satisfactory agreement with the HE-FUS3 experiment for all the steady state and the transient tests. Needs for future code developments and for the experimental loop improvements are suggested.