位于Tennessee州，靠近 Spring City，Watts Bar Nuclear Plant 的Unit 2 冷却塔的内部，摄于 April 29, 2015. MARK ZALESKI/AP
今年晚些时候, 一座核反应堆将会第一次开始启用<open>，这也是美国二十年内第一次启用核反应堆。但是这个名为Watts Bar Unit 2反应堆 —Tennessee州Spring City附近两座反应堆其中的一座, —一点也不崭新 <isn’t quite new>。该反应堆的大部分在1970s and ’80s就和Unit 1一起建造好了，而Unit 1在1996年并网<came online>，并运行得很完美。这两座反应堆在安全性，技术水平和输出能力上基本一致，但启用时间的20年时间差之间发生了一项大的变化：化石燃料对气候改变影响的看法以及使经济发展脱离化石燃料的紧迫性被广泛接受。
In the years that Watts Bar 2 lay fallow, policymakers and climate strategists have struggled to figure out what the future of renewable energy will look like. They have three options: find a way of cleaning up coal, build batteries capable of storing energy from capricious renewables, or go nuclear. Each has benefits and drawbacks. But nuclear is a strong contender because it is the only technology that actually exists. The Watts Bar reactors will provide power to 1.5 million households, and their only greenhouse gas emissions will come from the cars employees use to commute.
That’s a good deal, but still. Show a crowd a pair of cooling towers, and at least some of them will see an atomic apocalypse featuring three-eyed fish, leafless forests, and hospital-gowned Soviet defectors with skin like glistening mayonnaise. Nuclear power may be clean, but people still question whether it is, or ever will be, safe enough.
Those fears may be moot. Safety concerns didn’t delay construction on Watts Bar Unit 2 for so many years. Economics did. For all that fear, nuclear power still has the safest track record of any power source.
Nuclear energy sources are dangerous because they emit radiation—particles and energy shed from unstable molecules trying to calm down. “Those radioactive missiles can hit the human body and damage cells or DNA,” says David Lochbaum, director of the Union of Concerned Scientist’s nuclear safety project. Enough radiation will give you cancer, or possibly even pass genetic mutations on to your kids. Too much can kill you outright.
But plants like Watts Bar don’t release much radiation into the environment. Inside, radioactive material heats water, which turns into steam, which spins the enormous turbines that generate electricity. Plants regularly release some of that water and steam at rates prescribed by the US Nuclear Regulatory Commission, and if you live downriver or downwind of one, the radiation within will raise your chances of developing a tumor by just one tenth of one percent. You’re far more likely to grow a tumor because you sneak a cigarette now and again.
But you aren’t afraid of routine releases. You’re terrified of another Three Mile Island, Fukushima, or Chernobyl.
These disasters were the result of a meltdown, which occurs when something impedes a reactor’s ability to cool the fuel. The US, where nearly 20 percent of electricity comes from 99 nuclear plants, uses uranium. Older reactors—which is every reactor in the US, including Watts Bar Unit 2—use electric pumps to move water through the system. The Fukushima disaster showed what happens it you have pumps but no power to use them. Newer generations rely on gravity instead, draining cooling water from elevated storage tanks to send it through the reactor core.
Those updates mean serious nuclear accidents are becoming ever more rare. Since Three Mile Island in 1979, the Nuclear Regulatory Commission found that the rate of shut-down-the-reactor-level problems has dropped from 2.5 per plant per year to around 0.1 (One such happened on March 29 in Washington). Even Three Mile Island wasn’t the disaster it could have been, because of that plant’s layers of redundant protection.
In terms of full blown nuclear disaster, there is really only one data point: Chernobyl. Which was horrifying. But in terms of real risk? The World Health Organization estimates the disaster will claim 4,000 lives, a figure that includes everything from direct victims to people born with genetic mutations well after the meltdown in 1986. By comparison, particulate matter from coal power plants kills about 7,500 people in the US every year. Radiation is the shark attack of environmental danger: An awful way to go, but far less likely than, say, a car wreck.
Spent fuel—about a third of the uranium in a reactor’s core is replaced every two years—is a bigger concern, because the US nuclear industry doesn’t have anywhere to dispose of it. Used rods sit in cooling tanks for five years, until they’re cold enough to encase in dry casks. But that fuel isn’t harmful unless you fall into the water (hello super powers! Actually, probably just radiation poisoning). Or the plumbing fails. Spent rods stashed away in dry casks are even less worrisome, because the containers would need to be breached enough to let air get in and cause a combustion.
所以核能，并不那么危险。要感谢这三件事：混凝土，管道工程和保护性维护工作！<Three cheers for concrete, plumbing, and preventative maintenance! > 现在安静下来<pipe down>，来听听一些反话：核工业之所以具有安全性，是因为在输出第一波电流之前<fist jolt of current>，在(环评)<permitting>，检查，材料，和特殊的建筑方式上花费了数十亿美元。这些花费阻止了核能这种安全而可持续的能源真正的走向现实。<And those costs are exactly what keep this safe, sustainable energy source from really happening.>
Watts Bar Units 1 和 2本该同时启用的。 但是从1973年修筑反应堆以来, 该地区的能源需求下降了。正是因为要完成两个反应堆的建造花费太高，两个反应堆在1988年被封存<mothballed>。能源需求的振兴使得Unit 1在1996年得到完工。反应堆的拥有者，Tennessee Valley Authority，在2007年投票恢复反应堆的唯一理由是这个机构的文职人员< pencil pushers >成功说服了机构的委员会和股东，（使他们相信）区域经济在接下来的年份内的增长可以创造出足够的需求。
这可能是核能的最大冒险因素：建造核能之后，要花太长的时间才能见到投资的收效，如果有收效的话<if one comes at all. >。假设你今天开始建造一座核电站。如果，在接下来的20年内的某个时刻，一群努力工作的天才发明了能够(良好)储存风电或者太阳能的电池，将煤炭造成的碳排放消除，或者（因不再需要开采而）解决了天然气的甲烷排放，那么你将核电站建好之后，你那昂贵的核能想在市场上占据一席之地的可能性非常渺茫。
“我们在最近7年观察到的现象是许多的旧核电站提前关闭了，因为它们在电力市场上不再具有竞争力”，来自Princeton University的Nuclear Futures Laboratory 的物理学家M.V. Rarama说。
甚至核能工业体制内的人员也觉得这个选择不太实际。“你可以提出这样一个强有力的论点，比如燃烧像核能一样特别的东西，来产生类似廉价而无处不在的电力一样的东西非常愚蠢。” 一位来自 University of Tennessee的核工程教授 Arthur Ruggles说。 如果在可再生能源方面能做到扩大应用范围、提高应用效率，整个社会也许就能够省下铀资源，并将其运用在一些炫酷的事物上，例如用它来驱动星际飞船。