4. Nuclear Power Plants 1 / 40

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1 4. Nuclear Power Plants 4. Nuclear Power Plants 1 / 40

2 Cross-Section of a Nuclear Power Plant In the steam power plants, the thermal efficiency of a fossil power plant is approximately 40%, and of a nuclear power plant is approximately 33%. The majority of this heat loss in a fossil power plant is fro the flue gases that flow out of the stack and from the condenser cooling water. In a nuclear plant, almost heat loss of 67% is to the condenser cooling water. The larger steam flow required in a nuclear plant, because of the lower steam pressure and temperature. 4. Nuclear Power Plants 2 / 40

3 Schematic of a Nuclear Power Plant A. Primary circuit B. Secondary circuit C. Tertiary circuit 1. Reactor 2. Fuel assemblies 3. Control rods 4. Pressurizer 5. Steam generator 6. Primary pump 7. Feedwater primary circuit 8. Feedwater secondary circuit 9. Steam secondary circuit 10. High- pressure turbine 11. Low-pressure turbine 12. Condenser 13. Feedwater pump 14. Generator 15. Exciter 16. Transformer 17. High voltage line 18. River 19. Intake cooling water 20. Cold cooling water 21. Warm cooling water 22. Cooling water 23. Upward airflow 24. Steam 25. Outlet cooling water 4. Nuclear Power Plants 3 / 40

4 Fluid Flow in a Nuclear Power Plant G nuclear reactor, 2-steam generator, 3-HP turbine, 4-steam separator, 5-reheater, 6-LP turbine, 7-generator, 8-condenser, 9 -condensate pump, 10-LP FWH, 11-LP FWH, 12-BFP, 13-HP FWH, 14-main circulating pump 4. Nuclear Power Plants 4 / 40

5 PWR System Outline 4. Nuclear Power Plants 5 / 40

6 PWR System Outline 4. Nuclear Power Plants 6 / 40

7 Schematic of a Nuclear Power Plant 4. Nuclear Power Plants 7 / 40

8 Schematic of a Nuclear Power Plant 4. Nuclear Power Plants 8 / 40

9 NSSS APR Nuclear Power Plants 9 / 40

10 Reactor Vessel 4. Nuclear Power Plants 10 / 40

11 Control Rod Drive mechanism 4. Nuclear Power Plants 11 / 40

12 Pressurizer [1/3] 4. Nuclear Power Plants 12 / 40

13 Pressurizer [2/3] The basic design of the pressurized water reactor includes a requirement that the water (reactor coolant or coolant) in the reactor coolant system not boil. Another way to put this is that the coolant must remain in the liquid state at all times, especially in the reactor vessel. To achieve this, the coolant in the reactor coolant system is maintained at a pressure sufficiently high that boiling does not occur at the coolant temperatures experienced while the plant is operating or in an analyzed transient. To pressurize the coolant system to a higher pressure than the boiling point of the coolant at operating temperatures, a separate pressurizing system is required. That is the function of the pressurizer. Although the water in the pressurizer is the same reactor coolant as in the rest of the reactor coolant system, it is basically stagnant, i.e. reactor coolant does not flow through the pressurizer continuously as it does in the other parts of the reactor coolant system. Pressure in the pressurizer is controlled by varying the temperature of the coolant in the pressurizer. Water pressure in a closed system tracks water temperature directly; as the temperature goes up, pressure goes up and vice versa. To increase the pressure in the reactor coolant system, large electric heaters in the pressurizer are turned on, raising the coolant temperature in the pressurizer and thereby raising the pressure. 4. Nuclear Power Plants 13 / 40

14 Pressurizer [3/3] To decrease pressure in the reactor coolant system, sprays of relatively cool water are turned on inside the pressurizer, lowering the coolant temperature in the pressurizer and thereby lowering the pressure. Because water is incompressible fluid, water in a connected piping system adjusts equally to pressure changes anywhere in the connected system. The water in the system may not be at the same pressure at all points in the system due to differences in elevation but the pressure at all points responds equally to a pressure change in any one part of the system. The pressurizer has two secondary functions. One is providing a place to monitor water level in the reactor coolant system. The other secondary function is to provide a "cushion" for sudden pressure changes in the reactor coolant system. The upper portion of the pressurizer is specifically designed to NOT contain liquid coolant and a reading of full on the level instrumentation allows for that upper portion to not contain liquid coolant. Because the coolant in the pressurizer is quite hot during normal operations, the space above the liquid coolant is vaporized coolant (steam). This steam bubble provides a cushion for pressure changes in the reactor coolant system and the operators ensure that the pressurizer maintains this steam bubble at all times during operations. 4. Nuclear Power Plants 14 / 40

15 Coolant Pump 4. Nuclear Power Plants 15 / 40

16 PWR Steam Generator - Doosan 4. Nuclear Power Plants 16 / 40

17 PWR Steam Generator - WH 4. Nuclear Power Plants 17 / 40

18 PWR Steam Generator - CE 4. Nuclear Power Plants 18 / 40

19 Ideal Rankine Cycle - Nuclear T p 3 = p 2 q H 3 2s 2 p 4 = p 1 1 4s 4 q L s Process 12s : Isentropic compression in pump Process 2s3 : Constant pressure heat addition in steam generator Process 34s : Isentropic expansion in turbine (adiabatic turbine) Process 4s1 : Constant pressure heat rejection in condenser (h 4 >>h 1 ) This saturated-steam cycle is a basic Rankine cycle for nuclear power plants with non-reheat system. 4. Nuclear Power Plants 19 / 40

20 Moisture Separator Spinner Blades (Swirler) 4. Nuclear Power Plants 20 / 40

21 Moisture Separator Small Holes Wire Mesh Small holes on the separator wall have a function of water film extraction from a separator 4. Nuclear Power Plants 21 / 40

22 Grid System for a Steam Separator Cell Type: Tetrahedral Number of Cells: 1,281, Nuclear Power Plants 22 / 40

23 Path Lines of Steam Flow V in (m/s) = Nuclear Power Plants 23 / 40

24 Water Droplet Trajectories V in = 5m/s d p (m) = Nuclear Power Plants 24 / 40

25 Droplet Removal Efficiency in Steam Separator Droplet removal efficiency (%) Support Inlet Velocity (m/sec) Droplet size ( m) 4. Nuclear Power Plants 25 / 40

26 Steam Dryer Flow Spacer Vane Pocket Cross Section of Dryer Vane (Chevron Vane) Dryer Bank 4. Nuclear Power Plants 26 / 40

27 Velocity Vectors in a Dryer Vane V in = m/s; Parallel Vane Pocket 4. Nuclear Power Plants 27 / 40

28 Droplet Trajectories in a Dryer Vane [1/2] d p = 4 m 10 m 15 m 20 m 4. Nuclear Power Plants 28 / 40

29 Droplet Trajectories in a Dryer Vane [2/2] d p = 30 m 40 m 60 m 100 m 4. Nuclear Power Plants 29 / 40

30 Quality Distribution (Required) Quality around 25 % around 96~98 % should be higher than % Calculated Quality around 25 % 96 % (assumed) % 4. Nuclear Power Plants 30 / 40

31 Path Lines in a Steam Generator 4. Nuclear Power Plants 31 / 40

32 BWR System Outline 4. Nuclear Power Plants 32 / 40

33 BWR System Outline 4. Nuclear Power Plants 33 / 40

34 BWR 4. Nuclear Power Plants 34 / 40

35 BWR Moisture Separator Moisture Separator Swirler 4. Nuclear Power Plants 35 / 40

36 BWR Steam Dryer Assembly Steam Flow 4. Nuclear Power Plants 36 / 40

37 Cross-Section of Four Cylinder Turbine MSR (GE) 4. Nuclear Power Plants 37 / 40

38 State Changes in Nuclear Steam Turbines Moisture Separator Reheater To Feedwater Heaters From Main Steam Generator Exciter Main Electrical Generator LP Turbines HP Turbine Steam Dryers To Main Transformer Main Steam Condensate Pump [ Steam Turbine (APR 1400) ] Condensers To Feedwater Heaters 이그림에서잘못그려진부분? 4. Nuclear Power Plants 38 / 40

39 질의및응답 작성자 : 이병은 ( 공학박사 ) 작성일 : (Ver.1) 연락처 : ebyeong@daum.net Mobile: 저서 : 실무발전설비열역학 / 증기터빈열유체기술 4. Nuclear Power Plants 39 / 40