Natural and Gas Enhanced Circulation Tests in the NACIE Heavy Liquid Metal Loop

The paper reports on the results carried out from the natural circulation and gas-injection enhanced circulation tests performed on a heavy liquid metal loop, named NACIE, and located by the Brasimone ENEA Research Centre. The work is aimed at providing information on the characterization and interpretation of the basic mechanisms proposed in the design of future reactor relying on these circulation mechanisms. The results discussed in the present work concern the experiments performed using Lead Bismuth Eutectic (LBE) as coolant. Both natural circulation and gas-injection enhanced have been addressed, drawing conclusions about the observed phenomena. Numerical simulations have been performed in collaboration with the University of Pisa, adopting the RELAP5/Mod3.3 system code modified to allow for LBE as a cooling fluid. Post-test calculations have been performed to compare the code response with the experimental results under the natural circulation and gas enhanced circulation flow regime, allowing to qualify the adopted nodalisation as well as the performance of the code when employed on HLM loop. The available data will allow to validate and qualify numerical tools for engineering application, establishing a reference experiment for the benchmark of commercial codes when employed in HLM loop.