Optimizing the Design of the Steam-Receiving Perforated Sheet Used in the PGV-1000MKO Steam Generator

Abstract

The VVER-TOI reactor plant has for the first time been furnished with a new layout of steam generators in the NPP reactor building, according to which the steam produced in the steam generator is removed from it through one steam nozzle. The shift for using one steam-offtake nozzle results in that a nonuniform steam velocity field is produced in the separation volume between the evaporation surface and steam-receiving perforated sheets (SRPSs), which is caused by steam motion along the path with the lowest friction, and this can entail excessive carryover of moisture from the steam generator (SG). To obtain the necessary moisture-separation performance of a horizontal steam generator equipped with one steam nozzle, it is necessary to set up a uniform field of the steam velocity vector’s vertical component in the separation volume with limiting the pressure loss in the SG steam path down to the design value. Therefore, it is proposed to arrange nonuniform flow friction along the steam motion path from the evaporation surface to the steam line by using a variable SRPS perforation ratio. In this study, a set of optimization numerical analyses of the SRPS design for the PGV-1000MKO steam generator performed using the CFD methods was carried out for determining the perforation ratio. In carrying out the optimization numerical analyzes, the performance characteristics of the steam-receiving device equipped with one steam nozzle located in the steam generator’s upper part and consisting of more than 50 perforated sheets had to be made maximally close to the performance characteristics of the steam-receiving device equipped with ten steam nozzles. By using an elaborated computer model, a set of optimization numerical analyses of the SRPS design was carried out, and an optimized design version of the steam-receiving device with a variable perforation ratio for the PGV-1000MKO steam generator has been obtained.