ENEA has designed and manufactured an experimental mock-up (called Heavy liquid metal - pressurized water cooled tube - HERO) with seven instrumented full scale double walled bayonet tubes installed in CIRCE facility in order to provide integral test experiments which are representative of the ALFRED Steam Generator. The present paper summarizes the activities performed in support to the experimental campaigns in the HERO-CIRCE facility. In particular, preliminary calculations by means of RELAP-5 and pretest-experimental campaigns are given in this document.