Chichenin V. Improving the theoretical foundations and experimental methods for NPP circulating cooling systems energy efficient structures creation.

At Ukrainian NPPs turbines of different capacity and various commissioning dates are connected to the combined circulating cooling system (CCS) with common for all water-chemical (WChR) and thermo-hydraulic regimes (THR) specific with a single composition of additional water and never taking into account the design features of individual units’ condensers made of different metals. Moreover, in recent years, power units of Ukrainian NPPs are often operated at low loads. Such a practice leads to high costs of additional and purge water as well as involves the origination of a chain of circumstances that contribute to the accelerated formation of deposits of sparingly soluble salts and metal oxides on individual condensers, with components sludging, breaches in pipes integrity and emergency water suction. Efficient operation of such multi-unit power plants requires the use of individual VHR for each CCS monoblock unit. This research is devoted to the topical problem of increasing the reliability and efficiency of NPP equipment CCS long-term operation in order to increase the installed capacity utilization factor (ICUF) taking into account the installed capacity, service life of units, condensers and dispatching load due to the use of CCS individual THR and WChR as well as the additional and purge water quality. The analysis of existing scientific and technical approaches to the existing CCS WChR research for the purpose of insoluble salts deposits and metals corrosion prevention at the power equipment to provide a continued effective and reliable work of heat exchangers is carried out. The mathematical model for calculating the circulating water physicochemical composition in the process of its evaporation and conditioning in built-in VSU has been improved. A scientifically substantiated method of structuring individual units with serial and parallel power units with individual THR and WChR CCS connection has been created, taking into account the additional water physicochemical composition. Improved are the methods for THR and WChR main indicators calculating for circuits operating the conditioned purge water reiterative use with pre-included and /or embedded water cleansing, as well as such water integrated use for SG feed and heat networks water preparation after treatment on hybrid water treatment plants. Created is a two-stage scale model with THR and WChR automatic monitoring that allows reproducing and maintaining test modes and conditions in the specified ranges with the required accuracy and stability for a set time; that model has been adopted by State Enterprise “National Nuclear Energy Generating Company “Energoatom” for testing new WChR CCS. A method of CCS operation efficiency discrete control with THR and WChR indicators and deposits intensity values automatic monitoring by weight method on control samples with indicators archiving at database to determine WChR efficiency in the process of laboratory researches and industrial tests for water of various saltiness has been developed. Elaborated is the research methodology with designing devices (cassettes), which allow performing, in industrial conditions, a discrete analysis of deposits on heat exchange surfaces and metals corrosion during the entire working campaign of NPPs’ and TPPs’ CCS, during a given time period. A method for the differentiation of sparingly soluble salts and metals oxides deposits has been developed. The purge water is a valuable raw material and after its conditioning can be reused in the same or in other powerplant’s cycles which have lower requirements as to the feed water quality. A purge with a small saltiness and Kу or its part can also be used to feed less loaded thermohydraulic cycles of energy facilities when converting to individual WChR the separately structured CCS units consisting of unit cooling towers and condensers. At that it is possible to arrange individual WChR CCS in a separate NPP’s CCS by changing the quality of feed water and purge values for separate structures, depending on the power units control load and the condensers service life and condition. One of the advantages of such unit structuring refers to wide possibilities of individual WChR CCS units control aimed at increasing the entire NPP CCS economy and reliability with reduced additional water consumption, reuse of purge water and circulating water max Kу. When continued operation of all power facility’s units and short-term reductions of loading upon production considerations justified is the use of complex circulating cooling systems WChR calculation method that consists in calculating to assess the circulating water ionic structure and supersaturation with sparingly soluble salts, quality of additional water and size of purges. This technique allows the analysis of different schemes for cooler, and water-treatment facilities structural connection at CCCS units, as well as CCCS units structural connection multi-stage schemes.