Optimization of Minimum Temperature Differences in the Steam Reheater of a Turbine at a Nuclear Power Station

The effectiveness of nuclear power stations (NPS), alongside with their safety, is critical. Improving the quality in designing new power units is related closely with their economic effectiveness and competitiveness. A substantiated selection in the values of many controlled variables of the process (or thermal) scheme is of great importance in this case. It is essential that the value of controlled variables should correspond to the economic conditions of NPS operation, which will become effective a long time after selection of these values. The paper presents an optimization procedure for a long-term period of controlled variables for the thermal scheme of a steam turbine unit (STU). The equipment item to be optimized is a live-steam reheater of an STU. A header-type, two-stage platen reheater, which is a part of the separator-superheater (SSH) developed at AO VNIIAM, has been selected. The design of the reheater is described and its distinguishing features are outlined. The particularity of the proposed procedure is that it yields the results in the form of a complex parameter, including both external economic and operating parameters. Having found the values of these parameters timed to operation of a newly designed NPS, the obtained correlation enables one to determine specific values of the minimum temperature differences. The results for optimization of the minimum pressure difference in an SSH designed for a K-1200-6.8/50 steam turbine unit by this procedure are presented. The criterion of the optimal temperature difference was a change in the annual reduced expenditure at an NPS as compared to those in the reference case. The optimization problem was solved by the coordinate decent method. The data required for the optimization were calculated by the options of the thermal scheme of K-1200-6.8/50 STU using the SKHEMA software code developed at the Nuclear Power Station Department of NRU MPEI. The predicted minimum temperature differences can be used as the reference in designing new SSHs for power units at NPSs with a thermal scheme similar to that used in the considered problem.