核能發電現況與未來 施純寬榮譽退休教授國立清華大學核子工程研究所. Institute of Nuclear Eng. & Science, NTHU 1 國立清華大學核子工程與科學研究所

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1 核能發電現況與未來 施純寬榮譽退休教授國立清華大學核子工程研究所 Institute of Nuclear Eng. & Science, NTHU 1

2 大綱 前言 核能發電原理與核能電廠系統 國際現況 核電安全問題 核電的未來 結論 Institute of Nuclear Eng. & Science, NTHU 2

3 前言 Beginning of Nuclear Power Best Times in Nuclear Power Three-Miles Islands Accidents Chernobyl Accidents Global Warming, Inconvenient Truth Nuclear Renaissance Fukushima Accidents Open Policies, Strategy, Safety Institute of Nuclear Eng. & Science, NTHU 3

4 U-235 Fission Reactions Fragments U-236 fission Neutron U-235 In 1/10,000,000 s Neutron Neutron Gamma Fragments Neutron Institute of Nuclear Eng. & Science, NTHU 4

5 Fission Chain Reactions In the above example, two neutrons are generated from one fission. These new neutrons cause more fission reactions and generate more neutrons. Power production is twice as much in each consecutive generation. This is known as fission chain reaction. For commercial purposes, what we need is a steady release of energy under controllable manner. Institute of Nuclear Eng. & Science, NTHU 5

6 Fission Chain Reactions, Steady and Critical Fragment U-235 Neutron U MeV Fragment Captured and Release Gamma Escaped neutron U-235 Institute of Nuclear Eng. & Science, NTHU 6

7 Fission Chain Reactions, Steady and Critical In order to maintain a steady state of energy release, we need to have one neutron available (and one only) for U- 235 nucleus from the previous fission reaction where one neutron was absorbed. The situation is known as critical state. The chain reaction is on its own without the help from external neutron sources. Normally, 2-3 neutrons are released from a fission reaction. Institute of Nuclear Eng. & Science, NTHU 7

8 Fission Chain Reactions, Steady and Critical Neutrons can escape from the system. It also can be absorbed in other materials. On the average, if the number of neutron participating the fission reaction is greater than one after one neutron was absorbed in the previous fission, the fission power would be increasing. On the other hand, if it is less than one, the power would then be decreasing. Institute of Nuclear Eng. & Science, NTHU 8

9 Neutron Cycle Absorbed in U-235 Fission Fast Neutron Moderation Absorbed in Fuel Diffusion Thermal (slow) Neutron Institute of Nuclear Eng. & Science, NTHU 9

10 Neutron Cycle Neutron cycle refers to a process where neutrons are absorbed and new neutrons are released from fissions and then absorbed again. Fission neutrons have high energies and are known as fast neutrons. Fast neutrons are moderated to energies at thermal equilibrium and becomes thermal neutrons. Thermal neutrons are much easier to cause U-235 fission reactions than fast neutrons. Institute of Nuclear Eng. & Science, NTHU 10

11 核能發電與火力發電 Steam out Turbine/Generator Nuc. Core Nuc. Boiler Core Condenser Waste heat cooling Cold water in Institute of Nuclear Eng. & Science, NTHU 11

12 常見核能電廠系統 Two main types of reactors exist. Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR). Water in a BWR core boils at system pressure and generate steam directly from the core. The steam is then used to run turbine and produce electricity. In PWR, water in the core does not boil due to high system pressure. Hot water is directed to Steam Generators to produce steam from water in a secondary loop. Institute of Nuclear Eng. & Science, NTHU 12

13 Institute of Nuclear Eng. & Science, NTHU 13

14 PWR Pressure Vessel Institute of Nuclear Eng. & Science, NTHU 14

15 Shielding and Containment Other important systems under normal operations include shielding and containment. Containment and its massive concrete structures provide effective radiation shielding. Steel liner inside containment serves as leak tight barrier to prevent leakage of radioactive materials. Institute of Nuclear Eng. & Science, NTHU 15

16 PWR Containment Institute of Nuclear Eng. & Science, NTHU 16

17 BWR Containment Institute of Nuclear Eng. & Science, NTHU 17

18 BWR Containment Institute of Nuclear Eng. & Science, NTHU 18

19 BWR Nuclear Power Plant Containment Steam out Water in Turbine Generator Vessel Condenser Suppression Pool Cooling Sea Water Institute of Nuclear Eng. & Science, NTHU 19

20 Economic Simplified Boiling Water Reactor. Institute of Nuclear Eng. & Science, NTHU 20

21 Institute of Nuclear Eng. & Science, NTHU 21

22 Pressurizer PWR Nuclear Power Plant Containment S.G. Steam out Water in Turbine Generator Condenser Vessel Cooling Sea Water Institute of Nuclear Eng. & Science, NTHU 22

23 Reactor Core Isolation Cooling System (RCIC) The equivalent one to the auxiliary f/w system in PWR. Designed to provide adequate water inventory in the core in the case the reactor becomes isolated from the turbine. Takes water from condensate storage tank, and injected into the vessel via f/w line. Backup water source is the pressure suppression pool. RCIC pump is driven by a small turbine which takes steam close to reactor steam outlet nozzles. Power for the control of the system is drawn from station batteries. Institute of Nuclear Eng. & Science, NTHU 23

24 Auxiliary Feedwater System (AFWS) Provides a continuous supply of water to the secondary side of the steam generator in case the main feedwater system becomes unavailable. It also can be used as an alternate to the main feedwater system during startup, hot standby, and cooldown. Redundancy and diversity. Main source of water: condensate storage tank, makeup water tank. Manually operated valves. Related systems: residual heat removal system (RHR), high pressure injection system (HPIS). Institute of Nuclear Eng. & Science, NTHU 24

25 台灣與國際核電現況 確保核安穩健減核打造綠能低碳環境逐步邁向非核家園 一 不限電 二 維持合理電價 三 達成國際減碳承諾 Institute of Nuclear Eng. & Science, NTHU 25

26 台灣與國際核電現況 101 年發購電量 再生能源 3.4% 其中水力 2.6%, 風力及太陽能 0.77% Institute of Nuclear Eng. & Science, NTHU 26

27 台灣與國際核電現況 運轉中機組 :16 部興建中機組 :29 部規劃中機組 :51 部提案中機組 :120 部 三明核電廠 300 km 蒼南核電廠 寧德核電廠 230 km 方家山核電廠秦山核電廠 三門核電廠 430 km 福清核電廠 155 km 漳州核電廠 270 km 防城港核電廠 陽江核電廠 肇慶核電廠 韶關核電廠 台山核電廠 嶺東核電廠 570 km 大亞灣嶺澳核電廠 海豐核電廠 500 km 陸豐核電廠 430 km 昌江核電廠 計畫興建與興建中運轉中 Institute of Nuclear Eng. & Science, NTHU 27

28 福島事件後有三國表示將廢核 已經擁有核能電廠的國家, 共 31 國 持續發展 美國 加拿大 法國 英國 俄羅斯 捷克 韓國 中國 印度 等 25 國 保留彈性 日本 台灣 瑞典 放棄核電德國 (2022 年 ) 瑞士 (2034 年 ) 比利時 (2025 年 ) 計畫興建首座核能電廠的國家, 共 18 國 計畫如常 計畫延後 沙烏地阿拉伯 阿拉伯聯合大公國 越南 土耳其 波蘭 印尼 泰國 放棄計畫 義大利 Institute of Nuclear Eng. & Science, NTHU 28

29 國際核電現況 Institute of Nuclear Eng. & Science, NTHU 29

30 國際核電現況 Institute of Nuclear Eng. & Science, NTHU 30

31 國際核電現況 Institute of Nuclear Eng. & Science, NTHU 31

32 核電安全問題 台灣地理位置的特徵 能源的多樣性,All-of-the-Above 能源政策, 能源配比 風險觀念的兩個要素, 第一是某段時間內該系統失靈的機會, 但是失靈機會大的並不代表對環境社會有大的威脅 所以, 第二就是要考慮一旦發生失靈後, 會有怎樣的後果 ( 通常是以生命或財產的損失來衡量 ) 這兩項的乘積, 就是代表所謂的風險 台灣每年車禍致命大約三千人, 每人每年車禍致命平均風險便是約萬分之一 Institute of Nuclear Eng. & Science, NTHU 32

33 核電安全問題 但是對於單一事故而後果嚴重的大型災變, 既使有相同風險, 民眾接受的態度與針對每天都在發生, 甚至習以為常者, 還是不一樣 所以工程師對於此類事故的做法, 便是努力降低發生意外的機會, 同時也要求更低的風險, 期望大家願意接受 零風險的迷思, 以及多安全才算夠安全 (How safe is safe enough) Institute of Nuclear Eng. & Science, NTHU 33

34 核能安全, 深度防禦 Concrete Containment Steel Liner Pressure Vessel Fuel Pellets And Rods Institute of Nuclear Eng. & Science, NTHU 34

35 核能安全與核廢料 Institute of Nuclear Eng. & Science, NTHU 35

36 耐海嘯設計 ( 龍門電廠 ) Institute of Nuclear Eng. & Science, NTHU 36

37 耐海嘯設計 ( 龍門電廠 ) Institute of Nuclear Eng. & Science, NTHU 37

38 耐海嘯設計 ( 龍門電廠 ) Institute of Nuclear Eng. & Science, NTHU 38

39 核電的未來 Gen-IV Nuclear Power Reactors. Sustainability, Economics, Safety and Reliability, Proliferation Resistance and Physical Protection. Gas-Cooled Fast Reactor System (GFR), Lead-Cooled Fast Reactor System (LFR), Molten Salt Reactor System (MSR), Sodium- Cooled Fast Reactor System (SFR), Supercritical-Water-Cooled Reactor System (SCWR), Very-High-Temperature Reactor System (VHTR). Small Modular Reactor (SMR) Institute of Nuclear Eng. & Science, NTHU 39

40 永續核能 Only one neutron out of two to three fission neutrons in every fission is needed to maintain criticality. Should any of the rest of the neutrons participate in the following reactions, new fuel is then actually produced. Conversion. If more fuel is produced than the amount of fuel consumed, it is known as breeding. 232 Th (n,g) 233 Th (b-) 233 Pa (b-) 233 U. 238 U (n,g) 239 U (b-) 239 Np (b-) 239 Pu. Institute of Nuclear Eng. & Science, NTHU 40

41 永續核能 99.3% U-238 and 0.7% U-235 in natural uranium. Known useful fissile isotopes are U-233, U- 235, Pu-239. Only U-235 exists in nature. There are plenty of U-238 and Th-232 in nature. Where are they? India has about 25% of all thorium in the world. Institute of Nuclear Eng. & Science, NTHU 41

42 核廢料處置 各種人類活動都會產生廢料, 放射性核廢料, 化學及工業廢料 各種核能應用, 如發電, 醫用, 工業用, 農業用, 商業用, 居家用等, 都會產生核廢料 特性是他們都有長短不一的半衰期, 而且最重要的是放射廢料體積很小 各種工業有毒廢棄物, 對於人體健康威脅十分嚴重, 特性是這些東西不會隨時間消失, 且體積又十分龐大 各種廢棄物全世界共通的解決方法就是掩埋 一般工業廢棄物也有可能被故意加以稀釋排放, 放射性廢棄物則是濃縮 減容 Institute of Nuclear Eng. & Science, NTHU 42

43 核廢料處置 法國做法是淺埋, 方便管理 瑞典芬蘭要深埋, 遠離生物圈 管制法規要求針對核廢料處置, 核能電廠要建造且維護 收拾 保管所有會跑到環境的排放物的設備 火力電廠的排放物呢? 是不是也可以制定法規要求火力電廠將其產生的溫室氣體 煤渣等也收拾打包, 自行保管? Institute of Nuclear Eng. & Science, NTHU 43

44 Final Words Before Fukushima. After Fukushima. Risk of global warming. Renewable energy resources. Sustainability Institute of Nuclear Eng. & Science, NTHU 44

45 謝謝 Institute of Nuclear Eng. & Science, NTHU 45