双语阅读-福岛核事故之后的核安全反思.docx

Nuclear Safety After FukushimaEven with events at Japans Fukushima Daiichi nuclear power complex still in a state of flux, attention is shifting from containment to assessment. The 9.0 magnitude earthquake, hundreds of aftershocks and ensuing tsunami were historic. But they can hardly be called unforeseeable, and therein lies the nub of the critical questions this incident will raise for regulators everywhere: To what extent should nuclear safety regulation take account of all foreseeable contingencies, and should new technologies be required to apply to pre-existing facilities that were built to the standard of the industry at the time of construction?The six-reactor Fukushima Daiichi facility was commissioned in 1971 andby designsuccessfully withstood the March 11 earthquake and its aftershocks. But the tsunami topped the facilitys sea wall, knocking out the back-up diesel generator and forcing the pump cooling systems and pressure ventilators to rely on batteries until mobile generators could be delivered to the site. Water also flooded the basement where switching equipment connected the pumping equipment, impeding repairs.The result was overheating that caused pressure to build to over two times the designed limitations and led to explosions at three of the reactors. The outer buildings were designed to contain the reactor and to withstand severe weather conditions, but not hydrogen explosions. Radiation leakages resulted, causing widespread concerns about threats to health and the environment.Such a chain of events, however extraordinary, cannot be said to be unforeseeable. Japans infrastructure and regulatory framework have anticipated earthquakes for 150 years; power outages, tsunamis and widespread demands that strain response efforts are all predictable consequences of earthquake risk.Indeed, engineers have already designed solutions to mitigate the risks that materialized at Fukushima. Todays third-generation nuclear reactors anticipate the possibility of failed cooling systems and hydrogen pressure build-ups. The Westinghouse AP1000 reactor has a series of passive cooling systems that operate without external or diesel-generated power or activation by its operators. It also has recombiners that prevent hydrogen explosions.This design has been officially adopted in China for all inland nuclear projects where earthquake risks are more prevalent than on its coasts. Arevas EPR reactor under construction in Finland, France and China has four independent emergency passive cooling systems and extra core containment areas around the reactor. And Mitsubishis new APWR has passive and active redundant cooling systems.So why werent these technologies installed at Fukushima? Nuclear safety regulators around the world assess risks associated with nuclear power facilities on the basis of the technology to be deployed and the location and range of events that potentially could threaten the safety or control of the facility. Even after construction, regulators are given wide discretion to impose additional requirements on the equipment, systems and procedures used at a given facility.The problem is how to decide when to require plant operators to implement costly refits of new technology on older plantsand this is where Japans regulators could ultimately come in for some justifiable scrutiny. This is a question of both engineering and cost-benefit analysis. While certain modular equipment and control systems in nuclear plants can be upgraded, integral parts of the reactor chamber or housing cannot be easily removed, disposed of and replaced due to the presence of radioactivity.This means that in some cases the choice may not be whether or not to upgrade, but whether to shut down entirely. Given those options, operators and regulators are inclined to maintain the status quo instead of requiring the application to old facilities of newer systems to more effectively address risks that can seem quite remote. Fukushima may cause a rethink of this approach not only in Japan but around the world.Japans experience also suggests regulators and emergency planners need to think more realistically about the circumstances under which an emergency is likely to occur. Most nuclear safety regulations are based on a scenario where a singular disaster occurs at a specific facilityakin to Chernobyl or Three Mile Island, incidents that arose due to circumstances within the plants themselves or external events affecting their immediate vicinity.That approach to planning can leave officials unprepared for what has happened at Fukushima: a nuclear incident as part of a much larger disaster. In the aftermath of the Sendai earthquake, response teams and resources were required to cover an area of 35,000 square miles, in which two million people were without power, water or food, and roads, airports and other infrastructure were severely damaged. More far-sighted planning would have anticipated the limitations on emergency services in such circumstances.Finally, regulators need to account for the societies and particular cultures they cover. Japans great wealth, technological advancement and quality infrastructure made it remarkably resistant to the ravages of a great earthquake and horrific tsunami. And the high levels of education and the renowned discipline of its people certainly helped it avoid apocalyptic consequences. While this hasnt averted the problem at Fukushima, it does mean the country was better equipped to deal with such an event than others might have been.Regulators in Vietnam, Malaysia, Thailand, the Philippines, Indonesia and other developing nuclear aspirants that ring the fault lines of much of the Pacific Ocean need to candidly assess their nations capacity to respond in similar circumstances. Would they have the resources to deal with a Fukushima-style incident, even apart from any question about the quality of pre-disaster planning?At some point in the future even the most modern nuclear power systems on todays drawing boards will appear antiquated compared to the days technology. Fukushima should give regulators both today and tomorrow pause in how they approach the issue of safety in the face of technological evolution.(Mr. Stephens is a Hong Kong-based senior partner with the law firm Orrick, Herrington and Sutcliffe. )福岛核事故之后的核安全反思尽管日本福岛第一核电站仍然处于不稳定状态，但目前关注的焦点已经从控制转向评估。强达9.0级的地震、成百上千次余震以及由此引发的海啸都已经成为过去。但 是，这些都不能说是不可预见的事件，这也正是此次事故给全球监管机构提出的一系列重要问题的核心所在：核安全监管机构应该在多大程度上考虑所有可预见的意 外事件？那些按照原先的行业标准建造的已有设备是否需要采用新的技术？拥有六个核反应炉的福岛第一核电站从1971年开始运行，从设计角度来看，它成功经受住了3月11日的地震及余震的考验。但是，海啸冲破了核电站的海堤， 摧毁了后备柴油发电机，导致冷却泵系统和压力通风装置在移动式发电机被送抵现场前需要依靠电池来工作。海水还灌进了连接转换设备和冷却泵的地下室，阻碍了 维修工作。由此带来的过热问题导致压力升高至设计极限的两倍多，并导致三个反应堆爆炸。根据设计，用于包裹反应堆的周边建筑能够经受恶劣天气状况的考验，但承受不了氢爆炸的冲击。爆炸导致放射性物质外泄，使人们普遍担忧身体健康和环境受到威胁。虽然这一系列事件都非同寻常，但不能说是不可预见的。日本的基础设施和监管架构预先考虑了未来150年可能发生的地震；供电中断、海啸以及考验应急能力的各种需求都是可预见的地震后果。事 实上，工程师们已经设计出了能够减轻风险的解决方案，虽然对福岛核电站来说这些风险已经不幸成为现实。如今的第三代核反应炉考虑了冷却泵系统失灵和氢压增 大的可能性。美国西屋电气(Westinghouse)建造的AP1000反应堆拥有一系列不需要外部电源或柴油发电机的被动冷却系统，也不需要操作人员 起动。这个反应堆还配备了防止氢爆炸的复合装置。这项设计已经正式被中国采纳，推广到所有内陆地区的核电站专案，这些地区发生地震的危险要大于沿海地区。阿海珐集团(Areva)的EPR反应堆拥有四个 独立的紧急被动冷却系统，反应堆外面还有一个额外的核心包围区，目前正在芬兰、法国和中国建造。三菱重工(Mitsubishi)的新APWR反应堆拥有 被动和主动后备冷却系统。那么，这些新技术为什么没有被应用于福岛核电站呢？全球各国的核安全监管机构都要根据将被采纳的技术、场所和一系列可能威胁设备安全及控制的事件来评估核电设备的相关风险。即使是在核电厂建成之后，监管机构还有广泛的权力对某个电站的设备、系统和程式追加更多要求。问 题是，监管机构怎样决定何时要求电厂运营商对旧厂进行代价不菲的技术更新呢？这正是日本监管机构在进行合理审查时最终可能触及的问题。这既是一个工程技术 问题，也是一个成本效益分析问题。虽然核电站的某些模组设备和控制系统可以进行升级，但由于存在辐射，反应堆周边建筑的主体部分不能被轻易移除、处置或替 换。这就意味着在某些情况下面临的选择就不是核电站升不升级的问题，而是是否彻底关