Analysis of the Water Chemical Regime at an NPP with a VVER-1000 before and after Reconstruction of the Turbine Condenser’s Tube System

Abstract

Requirements for improving the reliability, safety, and efficiency of nuclear power plants, as well as increasing the service life of the main NPP equipment up to 60 years, leads to the need to introduce new and improve existing technologies for maintaining water-chemical regimes. One of the directions of such improvement is the decommissioning of equipment and pipelines made of copper-containing alloys. For the operating NPPs with VVER-1000, AO Rosenergoatom Concern developed and implemented a program to replace the turbine condenser’s tube system with one made of stainless steels or titanium alloys. Such replacement of the equipment of the secondary circuit made of copper-containing alloys was aimed at ensuring the safe and reliable operation of the steam generator (SG) and extending its residual life. The implementation of the program has significantly increased the reliability of the turbines and equipment of the condensate-feed tract and provided the suction of cooling water at the level of worldwide values. The condenser’s tube system of NPP turbines for cooling water with low- or medium salinity is made of stainless steel, while it is made of titanium alloy for cooling water with high salinity. This article analyzes the water chemistry regime at NPPs with a VVER-1000 before and after the reconstruction of the turbine condenser’s tube system. The calculations and analysis of the water chemistry management presented in the article were carried out according to the measured concentrations of impurities in the “salt” sections of the SG, since the content of impurities in the feed water and condensate, as a rule, was less than 1 μg and is at the lower limit of sensitivity of the methods and devices used.