Abstract: This paper describes the characteristics of the 2X1000MW condensate polishing system and equipment in the Ling'ao nuclear power station phase II in Shenzhen, as well as the practical application of key technologies such as the high-tower separation method. Keywords: condensate; polishing system; resin separation The nuclear power unit is equipped with a full-flow condensate polishing system. The main characteristics of this system are large water volume , high influent DH value, strict water quality requirements, high safety factor, and high stability requirements. The function of the condensate polishing system (ATE system) is to remove suspended and ionic impurities from condensate, ensuring that the secondary loop water quality meets the requirements and WANO chemical indicators. This reduces corrosion and scaling of thermal system equipment, extends equipment lifespan, significantly reduces system flushing time during unit startup, allows for faster unit operation, and saves demineralized water usage. In the event of a seawater leak in the condenser, it prevents impurities from entering the conventional island's thermal system and provides operators with ample time to take appropriate measures. Therefore, researching the application of condensate polishing systems in nuclear power plants has broad prospects and profound significance. 1. Overview Nuclear power plants typically consist of a primary loop and a secondary loop system. The core of a nuclear power plant is the reactor. During the steam-water circulation process, due to the strong radioactivity of the nuclear reactor, the coolant flowing through it carries a certain degree of radioactivity. Therefore, the coolant flowing from the reactor must not leak into the secondary side water of the steam generator; otherwise, it will cause radioactive contamination of the secondary loop system. The key to preventing coolant leakage from the reactor into the secondary side water of the steam generator is to control the feedwater quality to prevent damage from intergranular corrosion or stress corrosion of the steam generator tube sheet. Furthermore, steam generator piping is difficult to replace; therefore, the requirements for the feedwater quality of the steam generator are higher than those for conventional high-parameter thermal power units. The overall layout of the 2x1000MW condensate polishing station (ATE system) of the Shenzhen Ling'ao Nuclear Power Plant Phase II was designed by the Guangdong Provincial Electric Power Design Institute (GEPDI) and supplied by China Huadian Engineering (Group) Corporation. 2. Main Process Flow The condensate polishing system adopts a medium-pressure bypass polishing system, as shown in Figure 1. Condensate polishing is achieved by setting the full-flow condensate polishing system at the bypass position of the main condensate system. Considering that 5%–10% of the net condensate returns to the main condensate pipe and enters the inlet header of the polishing unit along with the untreated condensate, no bypass isolation valve is installed on the main condensate circuit. The condensate polishing system consists of two parts: a condensate polishing section and an external regeneration section. The advantages of this device are: to ensure system safety, no valves are installed on the bypass, so that in the event of a condensate polishing system failure, the water flow will automatically pass through the valveless bypass, preventing accidents caused by system water loss; on the other hand, due to the design of the condensate booster pump, when the pump is started, the operating resistance of the polishing system will be overcome, allowing the condensate to be discharged after bed treatment, thus maximizing system operational safety. 3 Condensate Polishing System Parameters and Water Quality Standards The parameters and water quality standards of the condensate polishing system are shown in Tables 1-3. [b]4 Characteristics of the Condensate Polishing System Equipment 4.1 Main Equipment Parameters (Single Unit)[/b] The main equipment parameters of the condensate polishing system are shown in Table 4. 4.2 Equipment Structural Features The pre-cation bed is a welded 16MnR carbon steel cylindrical container lined with silicone-free natural rubber. The equipment diameter is φ3200. Due to the high DH value of the condensate (9.7), the designed bed height is 1.3m (uncommon in domestic technology), employing the same structure as the high-speed mixed bed. The resin trap is also a 16MnR carbon steel cylindrical container lined with silicone-free natural rubber, with a diameter of φ800. It adopts a side-inlet, side-outlet structure to save space. To ensure the filter element gap flow area meets the requirements of the maximum condensate flow rate, six small-diameter reinforced filter elements (DN125) are directly welded to the perforated plate. This not only reduces the equipment diameter and height but also increases the filter element strength, making the filter element device lightweight and easy to disassemble and install. The mixed bed is the final barrier in the treatment unit. To achieve the most effective desalination, we chose a φ3200mm diameter, welded 16MnR carbon steel cylindrical container lined with silicone-free natural rubber, instead of the easier-to-manufacture, lower-cost, and technologically mature spherical tank. This is a rare choice in China. The inner wall of the equipment is lined with rubber and consists of a two-stage water distribution and inlet device, a resin inlet device, and an outlet device. The mixed bed resin separation tower is a key piece of equipment in the high-tower separation method. The welded carbon steel cylindrical container of the mixed bed resin separation tower consists of a φ1800mm cylinder at the bottom and a φ1800/φ2600mm conical section at the top, lined with silicone-free natural rubber. The inlet device is an upward-extending T-shaped wire-wound branch pipe with a wire gap of 0.30mm to facilitate impurity discharge. The outlet device is a dish-shaped orifice plate with a low-resistance dual-flow-rate 316L stainless steel water cap, ensuring the large flow rate required for flushing and facilitating the rapid discharge of impurities. The internal components of this equipment ensure uniform water distribution and collection, preventing excessively high flow velocities and flow deviations in certain areas. The working principle of the separation tower is as follows: After running in the high-speed mixed bed, the exhausted cation and anion exchange resins are fed into the separation tower through the exhausted resin inlet for backwashing and stratification. A uniform columnar water flow enters the separation tower through the water distribution device at the bottom. Because the cation resin has a larger specific gravity and particle size than the anion resin, their settling velocities differ during backwashing. By gradually reducing the backwash water flow rate, the cation resin slowly settles at the bottom of the equipment, while the anion resin slowly settles at the top. The middle section near the anion resin inlet is a mixing transition zone between cation and anion resins, and the area above the resin inlet is entirely composed of anion resin. This ensures that all resin leaving the inlet is anion resin. Anion resin is discharged from the anion resin outlet on the side wall of the separation tower via flushing water, while cation resin is discharged from the cation resin outlet at the bottom of the separation tower. After the resin is transported, the amount of resin remaining in the separation tower is controlled by a mobile photoelectric level gauge installed on the side wall of the separation tower. When the resin reaches the photoelectric level gauge, the signal from the level gauge is sent to the operation control room, causing the program control to automatically determine that the resin has been completely transported, thus ending the entire separation process. 5 Conclusion Since the completion of the Qinshan Nuclear Power Plant in December 1991, China has built four nuclear power plants: Qinshan, Daya Bay, Shenzhen Ling'ao, and Lianyungang Tianwan, with a total installed capacity of 9 million kW. The country plans to build at least 30 nuclear power units in the next 15 years, aiming to reach an operating nuclear power capacity of 12 million kW by 2010; and an operating nuclear power capacity of 40 million kW, accounting for 4% of the total installed capacity, with a nuclear power capacity under construction reaching 18 million kW by 2020. Therefore, the study of the application of condensate polishing systems in nuclear power plants has a very broad prospect and far-reaching significance. This system is currently under construction and is believed to have forward-looking reference value in the ever-developing field of condensate polishing in nuclear power plants. References: [1] Wang Hua. Condensate polishing in nuclear power plants. Water purification technology, 2002, (4)