The results of a study on the equalization of a non-uniform steam load using submerged perforated sheets (SPSs) are presented. The experimental data obtained at the PGV test facility and calculations performed using the STEG code are used. The PGV test facility comprises a model of the horizontal steam generator used for Russian type water-water energetic reactors. A short description of the 3D thermal–hydraulic code STEG is presented. Tests for determining the equalization capability of the SPSs are performed using a non-uniform steam supply on the hot and cold sides of the test facility. The equalization of the steam flow rate is estimated using experimental pressure drops through the SPSs. Furthermore, a detailed analysis of the tests conducted with the STEG code has been performed. The SPS perforation degrees, which improve the equalization of the non-uniform steam load, are found using the STEG code.