基于本质安全的反应堆设计路径

1. 基于本质安全的反应堆设计路径 李宁 教授，院长 Oct. 2013

2. 经盟国家事故死亡频率Fatality Frequencies in OECD Countries • 比较1969-2000间经合组织国家能源事故导致死亡发生频率和死亡率的曲线。核电系统的结果是根据核电厂中系统专职概率安全评价体系得到的,它反映的是潜在死亡率。 Comparison of OECD data. Nuclear curve is based on safety assessment. LNG Coal Hydro Gas Oil Nuclear

3. 福岛事故突破了纵深防御Fukushima Breached Defense-In-Depth

4. 福岛事故是“黑天鹅”吗？Is Fukushima Accident a “Black Swan”? • “黑天鹅”是具备以下三种特征的极低概率事件 A BLACK SWAN is a highly improbable event with three principal characteristics: • 不可预测 It is unpredictable; • 后果严重广泛 it carries a massive impact; • 事后人们会编出理由来解释，使之显得不那么随机，更可预测 and, after the fact, we concoct an explanation that makes it appear less random, and more predictable, than it was. 核电安全标准大幅提升 公众接受程度快速下降

5. 经盟国家事故死亡频率Fatality Frequencies in OECD Countries • 比较1969-2000间经合组织国家能源事故导致死亡发生频率和死亡率的曲线。核电系统的结果是根据核电厂中系统专职概率安全评价体系得到的,它反映的是潜在死亡率。 Comparison of OECD data. Nuclear curve is based on safety assessment. LNG Coal Hydro Gas Oil Fukushima? Nuclear

6. 非经盟国家事故死亡频率Fatality Frequencies in non-OECD Countries • 比较1969-2000间非经合组织国家能源事故发生导致死亡发生频率和死亡率的曲线。 Comparison of non-OECD countries. Nuclear is based on Chernobyl data. Coal LNG Hydro Nuclear (direct) Gas Nuclear (indirect) oil

7. 核能发展面临的挑战Challenges in Nuclear Energy Expansion • 安全：轻水堆有潜在小概率严重事故可能性 Safety: Small but none-zero severe accident probability • 经济性：建造成本高、周期长、投资风险大 Economics: High capital costs, long construction time, large investment risks

8. 核能发展面临的挑战Challenges in Nuclear Energy Expansion • 可持续性：Sustainability: • 有限探明廉价铀资源，极低利用率 Limited U resource, very low utilization • 废物：长寿命放射性 Waste: Long-life radioactivity • 核扩散：特殊核原料，同位素富集、核燃料再处理中元素分离技术 Proliferation: Special nuclear materials, enrichment and reprocessing technologies

9. 费米为CP-1建立的多重安全保护Fermi’s Multiple Safeguard for CP-1 in 1942 • 3套“控制棒” 3 sets of “control rods” • Primary set for control of chain reaction • 2nd automatic rod linked to high reading • 3rd manual control rod heavily weighted, tied by a rope to be cut by “Safety Control Rod Axe Man” in emergency (SCRAM) • “液体控制队” “Liquid-control squad” • Pouring a Cadmium-salt solution

10. Rickover上将与核海军Admiral Rickover and Nuclear Navy • 实现将军的梦想需要高度重视安全 Rickover’s dream required a high regard for safety • 核海军的经验帮助打造了美国和世界的核工业 Trained personnel relied on experience gained from Nuclear Navy to build the nuclear industry in the US and overseas • 西屋被引进建设 Westinghouse was recruited

11. 美国反应堆安全顾问委员会Advisory Committee on Reactor Safeguards • 美国原子能委员会与1948年成立了反应堆安全防卫咨询委员会 ACRS was established by AEC in 1948 • defined its purpose as an instrument toward preventing any future loss of life in regular industrial operations • believed a single accident in industrial reactor could wreck hopes for peaceful atom • heeded lessons from Industrial Revolution that the final guide toward safety had to be experience in actual use • 1949年美国反应堆试验基地建立 National Reactor Testing Station was established in Idaho in 1949

12. 反应堆安全研究焦点领域Focus of Reactor Safety Research • 厂址 Plant Siting • 反应堆物理 Reactor Physics • 堆芯设计 Core Design • 燃料元件设计 Fuel Element Design • 机械与热工设计 Mechanical and Thermal Design • 沸腾传热 Boiling Heat Transfer • 热通道 Hot Channel Considerations • 反应堆控制 Reactor Control • 仪表 Instrumentation • 水化学 Water Chemistry • 屏蔽 Shielding • 安全壳 Containment • 事故缓解 Accident Mitigation

13. 轻水堆失冷事故的工程化安全防护Engineered Safeguard for LWR LOCA • 反应堆停堆保障关停链式核裂变 Reactor trip to provide positive and continued shutdown of the nuclear chain reaction • 应急冷却堆芯防止燃料熔化 Emergency core cooling (ECC) to prevent or limit fuel melting • 事故后散热以避免安全壳内压力过高 Post-accident heat removal (PAHR) to prevent containment over-pressurization • 事故后减少反应性以降低可能泄漏的放射性材料 Post-accident radioactivity removal (PARR) to reduce the radionuclide inventory available for release • 保障安全壳完整性以限制放射性泄漏 Containment integrity to limit radionuclide release

14. 应急堆芯冷却系统（ECCS）Emergency Core Cooling System (ECCS) • 1960年代末前，原子能委员会认为安全壳是终极独立防御线 Prior to end of 1960s, AEC viewed containment as the final independent line of defense • 1965-66年“中国症状”辩论聚集堆芯应急冷却系统 “China Syndrome” debates in 1965-66 brought ECCS into focus • 监管重心转向采用设计正确的ECCS运行来防止事故恶化到威胁安全壳的程度 Regulatory focus shifted to a properly designed and functioning ECCS to prevent accidents severe enough to threaten containment • 失冷事故和堆芯应急冷却系统成为轻水堆安全讨论中的主要话题 LOCA and ECCS have been major topics of public discussion of LWR safety

15. 质疑ECCS完善性和AEC角色ECCS Integrity and AEC Role Questioned • 1971年初，在爱达荷测试设施早期设计的ECCS实验中发现失冷事故时的高压蒸汽阻塞了来自ECCS的注水 Early 1971, tests of early ECCS design in Semi-Scale Facility at Idaho showed that the high pressure steam in LOCA blocked the flow of water from ECCS • 原子能委员会处理ECCS问题并同时担任核能推动者和监管者的双重角色受到批评 AEC’s handling of ECCS issues and role as both promoter and regulator of nuclear were criticized • AEC分成核监管委员会和联邦能源研究委员会（后成为能源部）AEC was split into NRC and FERC (later to DOE) • 原子能委员会的反应堆安全研究开发了概率风险评估方法 Probabilistic Risk Assessment developed in AEC’s “Reactor Safety Study” • 1979年3月28日，三里岛事故发生 March 28, 1979, TMI accident occurred

16. 三代加核电站设计目标Generation III+ Plant Design Objectives • 增加电站安全性 Increased Plant Safety • 多冗余或非能动 Additional redundancy or passive features • 减少操作员反应工作，更多时间 Reduced operator actions, more time • 降低堆芯损坏和大剂量泄漏风险 Reduced risk of core damage (CMF) and large release (LRF) • 堆芯熔化后保持包容系统完整 Severe accident features incorporated • Maintain containment integrity after core melt • 降低成本 Reduce Costs – Larger Plant Rating or Simplifications • 延长设计寿命 Increased Plant Design Life – 60 years • 缩短建造工期 Shorter Construction Schedules • 数字化仪控和主控室 Digital I&C and Compact Main Control Room

17. 先进水堆的共同设计特征Common Design Features in ALWR • 60年设计寿命 60-year design life • 4列安全系统 Four-train safety systems • 高于90%运行因子 More than 90% availability factors • 抗击外部撞击 External impact protection • 全数字化控制系统 Full digital control systems • 堆芯保存和稳定系统 Core retention and stabilization system

18. 先进水堆技术Advanced Water Cooled Reactor Technologies • 全球 Global • AP-1000 • EPR • WWER-1000/1200 • APR-1400 • APR-1000 • APWR • ABWR • ESBWR • ACR-700/1000 • ATMEA • 中国 China • CAP-1400 • CAP-1700 • ACP1000* • ACPR1000*

19. 先进水堆安全系统ALWR Safety Systems

20. 温伯格看反应堆安全Weinberg on Reactor Safety • "Atomic power can cure as well as kill. It can fertilize and enrich a region as well as devastate it. It can widen man's horizons as well as force him back into the cave." – in a 1945 Senate hearing • “现在的反应堆…充斥着安全系统加安全系统 – 安全与应急系统几乎主宰了整个技术 “Reactors are now… loaded down with safety system added to safety system – the safety and emergency systems almost dominate the whole technology.” – “Science and Trans-Science”

21. 安全与应急系统几乎主宰了核电技术Safety & Emergency Systems Dominate • 1350MWe ABWR

22. 解决方法Solution Options • 核电必须 Nuclear power needs to • 和其它电力技术竞争 Be competitive with other power technologies • 满足苛刻的安全要求 Meet advanced safety requirements • 用传统技术要同时解决以上问题会很困难 It is very difficult to simultaneously solve these two problems with the traditional nuclear power technologies • 通常以紧凑设计为基础，增加安全系统 Traditionally, developers design reactors for compactness, then add safety systems

23. 从安全基础的角度Fundamental Safety-based Perspectives • 反应堆灾害由 Hazards of reactors determined by • (F.1) 放射性：包含放射性总量 Radiation potential: total radioactivity (radiotoxicity) stored • (F.2) 放射性泄漏几率 Probability of radiotoxicity release • 灾害 Hazards = F.1 x F.2 • 因素1由反应堆功率决定，几乎与堆型无关 F.1 does not depend much of reactor type, but is determined by total energy output • 因素2与堆型密切相关 F.2 strongly depends on reactor types

24. 设计安全：可能路径Safety Through Design: Possible Paths • (P.1) 降低放射性 Reduce radiation potential (F.1) • Smaller total power • (P.2) 降低泄漏几率 Reduce probability of release (F.2) • (P.2.1) Decreased reactivity under abnormal conditions, inherent negative reactivity feedback • (P.2.2) Simple and rugged design for key components and systems • (P.2.3) Diverse and redundant means for critical safety functions • (P.2.4) Total stored potential energy • (E.1) Nuclear • (E.2) Thermal • (E.3) Chemical • (E.4) Coolant compression

25. 安全性分类Safety Types • (P.2.1) 固有安全性 Inherent Safety • 负反应性系数、多普勒效应、控制棒籍助重力落入堆芯等自然科学法则的安全性，事故时能控制反应堆反应性或自动终止裂变，确保堆芯不熔化。 Negative reactivity, Doppler effect, control rods drop into core under gravity etc, can control reactivity or stop chain reactions in accidents, ensure no core melt • (P.2.2-3) 非能动安全性 Passive Safety • 建立在惯性原理（如泵惰转）、重力法则（如位差）、热传递法则等基础上的非能动设备（无源设备）的安全性，即安全功能的实现毋需依赖外来的动力。 Based on inertia, gravity, heat conduction etc that use no supplied external power

26. 安全性分类Safety Types • (P.2.2-3) 能动安全性 Active Safety • 必须依靠能动设备（有源设备），即需由外部条件加以保证的安全性。 Rely on active powered equipment and external supplies • (P.2.2-3) 后备安全性 Redundant Safety • 指由冗余系统的可靠度或阻止放射性物质逸出的多重屏障提供的安全性保证。 Based on reliability of redundant systems, or multiple barriers to prevent release of radioactive materials

27. 降低放射性（路径一）Reducing Radiation Potential (P.1) • 低功率小型反应堆 Smaller reactors with lower power ratings • 世界范围有大量的小型堆开发项目 Many SMR (Small Modular Reactor, or Small and Medium Reactor) development programs worldwide

28. 改进燃料以降低事故后果Improve Fuel to Reduce Consequences 冷却液: 额外储存能量 包壳：间隔燃料和冷却液 燃料：主要放射性和能量源

29. 降低势能（路径二之一）Reducing Potential Energy (P.2.4) • 核能 Nuclear energy (E.1, see P.1) • 非核能 Non-nuclear energy (E.2-4) • 冷却剂固有性质 Inherent coolant property • 无法工程化去除 Cannot be engineered away

30. 冷却水的势能Potential Energy in Water Coolant • 热能 Thermal Energy (E.2) • 通过蒸汽膨胀转化为动能：对设备和包容设施造成机械破坏 Turns into kinetic energy via steam expansion: mechanically damage equipment & containment • Evaporation: loss of core cooling • 化学能 Chemical Energy (E.3) • 在严重事故中，蒸汽与锆化学反应形成氢气并释放热量，可能导致氢气爆炸 In severe accidents, steam chemically interacts with zirconium, releasing more thermal energy and hydrogen, potentially leading to hydrogen explosion

31. 不同冷却剂的势能比较Stored Potential Energy for Different Coolants G. I. Toshinsky, INES-3 (2010)

33. 调整风险因子配置Rebalance Risk Factors • 反应堆灾害= 后果x频率=F.1 x F.2 • 现行设计理念：通过纵深防御和冗余安全与应急系统降低频率F.2 • 为降低单位成本，加大反应堆功率和放射性F.1 • 核电最坏事故和后果（超设计基准事故）变得更为严重极端，降低核电的认可度 • 改变设计理念：平衡风险因子F.1 和F.2的分布！

34. 公众和市场欢迎/可接受的核电Nuclear Power Welcomed by Public & Market • 系统安全性保持良好 • 最坏后果范围和持续时间大幅减小 LNG Coal Hydro Gas Oil 未来核电事故？ Nuclear