Accoppiamento di codici CFD e codici di sistema in sistemi a piscina ed a loop

This report, carried out at the DICI (Dipartimento di Ingegneria Civile e Industriale) of Pisa University incollaboration with ENEA Brasimone Research Centre, deals with the modification of the relationshipused by the RELAP5 system code to generate the table of LBE, Lead and Sodium and with post-testthermo-fluidynamic analyses of NACIE loop type (Natural Circulation Experiment) facility and of CIRCEDHR (Circulation Eutectic- Decay Heat Removal System) pool type facility, built at ENEA. Experimental results are compared with those obtained from RELAP5 stand alone calculations and from RELAP5-FLUENT coupled code calculations. In particular, in the first part of this work the equations were modified into RELAP5/Mod3.3 system code to obtain the thermodynamic properties of lead, LBE and sodium and are presented for both saturation and single phase conditions. The second part of this work deals with post-test analyses of the NACIE loop type facility: computational results are obtained both from RELAP5 stand alone and from an in-house coupling tool achieved using RELAP5 thermal-hydraulic system code and CFD Fluent commercial CFD code. After that, a post-test simulation reproducing an accidental event with a total loss of the secondary circuit followed by a reactor scram and DHR system activation to remove residual heat generation, was performed using the RELAP5 code on Test IV of CIRCE facility experiments. Comparative analyses among the simulations performed by RELAP5-Fluent coupled codes and by RELAP5 stand-alone code agreed well, moreover results obtained for the CIRCE-DHR demonstrate the RELAP5 model’s suitability in simulating a PLOH+LOF transient representative experiment.