MELCOR Code Validation on HE-FUS3 Loop

Since the last decade, Tractebel Engineering has been involved in several consecutive projects in the field of High Temperature Gas Reactor (HTGR). The objectives of the present project called RAPHAEL (www.raphael-project.org) is to provide R&D results in order to consolidate available data on generic V/HTR technologies and to develop innovative solutions to further contribute to the improvement of HTR performances. One of the objectives of the RAPHAEL Sub-project Safety is to qualify tools for performing safety analyses and supporting the safety approach and demonstration. One of the work packages concerns the validation of the existing thermal-hydraulic system codes capabilities needed to perform transient analysis in V/HTR. This validation is carried out by benchmarking against experimental data and by comparing simulation results given by several codes. The current paper presents the work performed at Tractebel Engineering on the simulation of the HE-FUS3 experimental loop — ENEA facility, Brasimone (Italy) — with the MELCOR v.1.8.6 code. The HE-FUS3 loop contains a wide range of components characteristic of a V/HTR like compressor, pipes, diffusers, valves, heaters and heat exchangers. Even if the loop characteristics/configuration is not prototypical of a V/HTR design, the loop is useful to assess the objectives identified by the Project, i.e. helium operating fluid, design pressure and temperature set respectively at 10.5 MPa and 530 °C. The experimental data of the HE-FUS3 loop made available for the benchmark are a set of steady state tests for the thermal-hydraulic characterization of the loop and two transient tests — Loss Of Flow Accidents (LOFA). Moreover, to assess the characteristics of the compressor, data have also been provided from a compressor test campaign. From the code-to-experiment comparison the ability of MELCOR v.1.8.6 to reproduce the experimental results is judged.