Experimental and numerical analysis of heavy liquid metal systems for Generation IV fast reactors

The present work reports the results achieved during the doctoral research activity realized in partnership between DIAEE (Dipartimento di Ingegneria Astronautica, Elettrica ed Energetica) of Sapienza University of Rome and ENEA (Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile). The activities have been carried out within the EU scientific community, since they are part of the R&D activities foreseen in the two HORIZON2020 European Projects SESAME and MYRTE. After a brief description of the Lead Fast Reactors (LFRs) technologies and the actual status of the related R&D programs worldwide, the description of the Lead Bismuth Eutectic (LBE)-cooled pool-type facility CIRCE is presented. In particular, the work is focalized to the newest test section presently installed on CIRCE and named HERO (Heavy liquid mEtal pRessurized water cOoled tubes). The performed experimental campaigns aimed at characterizing a prototypical steam generator with double-wall bayonet tubes, evaluating its thermal-hydraulic performances in normal operational and transient scenarios. The experimental activity on CIRCE-HERO has been supported by a numerical pre-test analysis described in the third section of this document. In particular, the RELAP5-3D© model of the HERO secondary loop has been set-up and it has been used to define the start-up procedure of the facility and to achieve feedbacks on the performances of the steam generator. The core of this document is dedicated to the description and post-test analysis of the two experimental campaigns executed on CIRCE-HERO. The first experimental campaign, consisting of three tests, has been performed in the framework of the HORIZON2020 SESAME EU project, with the objective to support the development of the ALFRED design. The second one, consisting of nine tests, has been executed in the framework of the HORIZON2020 MYRTE EU project, with the purpose to support the development of MYRRHA and acquiring experimental data relevant for MYRRHA primary heat exchanger. To extend the knowledge and validation of SYS-TH codes when applied for LFRs, a simulation activity has been performed in the Benchmark exercise for SYStem Thermal-Hydraulic (SYS-TH) codes and CFD/SYS-TH codes validation, in the framework of the H2020 SESAME project. A RELAP5-3D© model of the NACIE-UP facility has been set up and it has been involved to perform a preliminary blind simulation activity and a subsequent post-test analysis on the basis of the experimental results available from the test performed on NACIE-UP. A final summary, conclusions and future perspectives are given in the final section of the document.