H2020 MYRTE CIRCE-HERO experimental campaign: post-test activity and code validation

In the frame of H2020-MYRTE (MYRRHA Research and Transmutation Endeavour) project, the LBE CIRCE facility, at ENEA-Brasimone research center, has been reconfigured with the HERO (Heavy liquid mEtal pRessurized water cOoled tubes) test section, consisting in a seven double wall bayonet tube bundle heated by LBE on the shell side and by water on the tube side. Despite having been conceived for tests aimed to the assessment of the ALFRED reactor heat exchanger, the experimental campaign in the MYRTE project foresees the facility to be used to simulate the behavior of the MYRRHA Primary Heat Exchanger in its innovative double-walled bayonet tube configuration. The thermal-hydraulic parameters characterizing the system are modified to represent MYRRHA plant conditions in terms of temperatures, pressures, void fraction and flow regimes. Its main purpose consists in studying the heat transfer process in the bayonet tube to characterize the convective and the conductive heat transfer processes and in comparing the experimental data with calculation models, for validation purposes. A RELAP5-3D model of the CIRCE-HERO facility has been realized and then used for a series of steady state pre-tests, which have been then compared with the experimental results performed in the MYRTE campaign. A number of discrepancies have been identified and explained. Finally, the model has been updated through the experimental feedback and the simulation accuracy has notably increased in terms of energy and momentum balance; the RELAP5-3D model is then able to provide an accurate experimental data representation.