SPES is an experimental facility that allows the assessment of thermal-hydraulic codes through the simulation of a wide range of physical phenomena characterising different accident scenarios in PWRs. The facility has full scale elevation and a volume scaling factor of about 1:400 with respect to commercial size PWRs. Water at real thermodynamic conditions is used both for the primary and the secondary circuits and the reactor full power can be simulated. In 1994 SIET performed a long experimental campaign on SPES-2 configuration giving a fundamental contribution to the AP-600 Reactor Certification Program. In 1999, ENEA, in order to restore the facility after five-year shutdown and in view of possible future programs, ordered SIET an experiment on a new configuration of SPES that was obtained by eliminating all the safety systems typical of advanced PWRs. This test, defined by a working group constituted by ENEA, ANPA, JRC Ispra, ANSALDO, Pisa University and SIET, consisted of a 10 equivalent break in Cold Leg, starting from full power and full pressure conditions. This paper reports the numerical results compared with the experimental ones. Moreover, it underlines the SPES facility capability to simulate IB-LOCAs in addition to SB-LOCAs and other kind of transients which it was designed for.