New Nukes

Leslie Dewan was 1 year old in 1986 when the Chernobyl nuclear plant in Ukraine melted down. Dozens of people died in the immediate aftermath of the catastrophe, and clouds of radiation spread over parts of Europe, contributing to thousands of excess cancer deaths. But the fallout experienced by the nuclear-power industry was almost as dire. Although the meltdown at Chernobyl had more to do with the failures of Soviet engineering than with nuclear power itself, the industry was dealt a crippling blow by the worst accident in its history. In the U.S., where memories of the partial meltdown at Three Mile Island in 1979 were still fresh, nuclear construction hit a standstill: no new plants were started for more than 30 years. For a smart young engineer like Dewan, who entered the Massachusetts Institute of Technology (MIT) as an undergraduate in 2002, the nuclear industry might seem like a dead end.

But that’s not how Dewan sees it. For the 28-year-old–and for a growing number of other young scientists interested in energy–Chernobyl is at most a dim memory. They see nuclear power as far from an existential threat to the planet but instead as the best way to save it, and they’re trying to revive the stalled industry with next-generation reactor designs that could change the way a skeptical public views atomic energy. Dewan just completed her doctorate in nuclear engineering at MIT, and in her spare time she co-founded a start-up called Transatomic Power, which has plans to build a safer and cheaper nuclear reactor, one that couldn’t melt down like the older plants at Chernobyl or Fukushima. “I’ve always been concerned about global warming,” she says. “It seemed to me like working in nuclear power was a logical way to do something to help the environment.”

We tend to pay attention to nuclear power only when something goes wrong, but for all its high-profile problems, nuclear has proven less deadly than almost every other form of electricity on a megawatt-by-megawatt basis. (Air pollution from coal, the top source of electricity in the U.S., contributes to the deaths of 14,000 people a year.) And aside from hydroelectric–which has mostly hit its growth limits and has its own side effects–nuclear is the only large-scale, always-on source of power that doesn’t contribute to global warming. If you know about energy and care about climate change–like Dewan–there’s no reason why you wouldn’t be attracted to nuclear. “I was always fascinated that something could produce so much energy with so little fuel,” says Jacob DeWitte, another MIT grad student and the founder of the micro-nuclear start-up UPower.

But it’s not just irrational fear that brought the nuclear industry to a virtual halt in the U.S. and much of the rest of the world. The costs of building new plants ballooned, with construction often coming in billions of dollars over budget. Outside of France, atomic plants weren’t standardized, which meant that nearly every reactor was produced bespoke–like a suit bought from a tailor instead of off the rack. The current generation of plants was derived from old Cold War technology, and as the Fukushima meltdown showed, those reactors are vulnerable to a sustained loss of power that shuts off the flow of cooling water to the nuclear fuel. Even though the health impact from the Fukushima fallout is likely to be minimal, the economic cost could exceed $100 billion. That’s a number that will be in the mind of any regulator considering a new nuclear plant–especially with competing natural gas so plentiful thanks to fracking.

So if nuclear is going to achieve what young engineers like Dewan and DeWitte are hoping for, the industry is going to need a new generation of reactors that are cheaper and safer. In the U.S., that will start with Southern Co.’s new Vogtle nuclear plants, which began construction in 2009 in northeastern Georgia. Southern is using a new reactor design: Westinghouse’s AP1000, the first Generation III+ reactor to be built in the U.S. (Generation I reactors were early prototypes; Generation II includes nearly all of the commercial reactors currently operating.) The AP1000 has passive safety features–in the event of an accident, the plant is designed to automatically shut down, with no need for human intervention or outside power for up to 72 hours. As a result, the AP1000 requires significantly fewer components, reducing the redundancies that have driven up construction costs in the past. And large sections of the plant are being built off-site in prefabricated sections before being shipped to the plant and welded into place. “The passive safety design allows you to get water to where it needs to be without an external power source,” says Tom Fanning, Southern Co.’s CEO. “That would have obviated a lot of the problems at Fukushima.”

The AP1000–and other new designs, like Areva’s EPR, currently being built in France, Finland and China–is evolutionary, not revolutionary. It still uses enriched uranium as fuel and ordinary water as the coolant, which means it doesn’t address concerns about nuclear waste or proliferation. But there are companies looking to take a bigger leap. One idea that’s grown popular is the small modular reactor (SMR). Designed to be about a third the size of traditional reactors, SMRs can shrink the multibillion-dollar up-front costs of a conventional nuclear plant. Less nuclear fuel means that even if something goes wrong, you won’t see the widespread radioactive contamination that can happen after a meltdown at a normal-size plant. Because they’re small and standardized, SMRs could be mass-produced and then shipped wherever they’re needed, which could mean an end to construction delays that can stretch to years. A number of small start-ups, like Hyperion and NuScale, have put forward SMR designs, and the Department of Energy agreed in June to provide $150 million to support the development of a Babcock & Wilcox subsidiary’s SMR design. Overcomplexity has always been the bane of nuclear technology–both in cost and safety. SMRs promise simplicity. “When you’re small, it just becomes a lot easier to manage everything,” says UPower’s DeWitte.

To really change the economics of nuclear, however, you need to fundamentally change how plants operate. That’s where Generation IV reactors come in. These designs–none of which has yet gotten to the prototype stage–alter the kinds of fuel and coolant that would be used, experimenting with mixes that potentially offer inherent safety, greater efficiency and less waste. Dewan’s company, Transatomic, is developing a molten-salt reactor. Instead of the familiar nuclear rods, it uses fuel dissolved in a salt mixture. At the bottom of the reactor vessel is a drainpipe plugged with solid salt, its temperature maintained with an electrical cooler. Should power be lost in a Fukushima-like accident, the plug would melt and the molten salt containing the fuel would drain into a storage area, where it would cool on its own. “You just coast to a stop,” says Dewan. The reactor would also be able to use the atomic fuel found in nuclear waste, which means more efficiency and less radioactive by-product.

The challenge of nuclear waste–another factor that has held back new construction in the U.S., since no one can agree where to put it–is also at the heart of another atomic start-up. TerraPower is experimenting with a traveling-wave reactor design, which would largely eliminate the need for uranium enrichment. (Traveling wave refers to the fact that fission occurs bit by bit in the reactor core, as if a wave of energy were slowly spreading through it, rather than in the entire core all at once as in standard fission.) In conventional reactors, composition of the isotope uranium-235 has to be increased in the fuel before it becomes fissile. TerraPower’s reactor design could use the depleted uranium found in nuclear waste, burning it for decades without refueling. If it works, the traveling-wave reactor–one of a number of designs TerraPower is researching–would be far more efficient than current designs, holding out the possibility of near limitless electricity. That revolutionary potential is what attracted Bill Gates, who is one of TerraPower’s main funders. “We think we could have a prototype by the early 2020s and become the commercial reactor of choice by the 2030s,” says John Gilleland, TerraPower’s CEO.

That’s the dream. The reality is that bringing any of these next-generation reactors to market would take billions of dollars and a lot of luck. It’s hard to imagine a private company shelling out that kind of capital up front on an idea that might never pay off–and it’s equally difficult to picture governments stepping up in an age of austerity. Nuclear critics fear that any design that would significantly reduce costs would inevitably skimp on safety. “As a general rule, the more excess safety margins you build in, the more expensive it’s going to be,” says Edwin Lyman, senior scientist at the Union of Concerned Scientists’ global-security program. “It’s a hump you can’t get over.”

That won’t deter Dewan or the rest of the young engineers working a nuclear renaissance, for whom climate change has changed the rules. “Everyone’s coming at this from an environmental perspective,” she says. “There’s a sense of possibility that we can invent new things in the realm of nuclear to save the world.” If a melting Arctic really is scarier than a meltdown, advanced nuclear might just have a chance.

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