Building A Safer, Cleaner Nuclear Reactor

One sidereal day in 2009, Leslie Dewan and Mark Massie were rummaging through old articles in an MIT library. There, they found two things the nuclear industry had abandoned a half century before. One was a sense of urgency : The first fast-neutron nuclear reactor had gone from scribbles on a diaper, in 1945, to a working prototype in only 18 months. The other was something called a melt salt nuclear reactor .
In the 1960s, scientists had operated one at Oak Ridge National Laboratory in Tennessee. But then support dried up, light-water reactors became the industry standard, and molten salt was all but forgotten. That seemed absurd to Dewan and Massey. Molten salt reactors, they learned, are safer than what ’ south used today. They burn fluent uranium fuel, quite than solid fuel, which reduces the opportunity of a meltdown. As part of a generation of youthful nuclear scientists motivated by climate change, and will to take a fresh look at nuclear power, Dewan and Massey wondered why the world wasn ’ t using this. They knew that to beat out cheap ember and natural gas, new reactors needed to be safer and more efficient. So they dusted off the Oak Ridge design and got to work .
today, their start-up, Transatomic Power, is poised to build a new, even better fade salt nuclear reactor. Their reactor will burn up to 96 percentage of its fuel, compared with only four percentage used by light-water reactors, and generate 75 times the electricity per short ton of uranium. It ’ randomness virtually accident-proof and can run on the spend fuel of other reactors. With closely 80,000 tons of radioactive pine away in the U.S. ( and with 2,000 tons added every year ), it could turn something toxic into something useful. “ That ’ s what sets Leslie Dewan and Mark Massie apart, ” says Richard Lester, steer of the nuclear science and engineer department at MIT. “ Their design addresses radioactive waste, which is huge. ”

Their reactor will generate 75 times more electricity per ton of uranium

thus army for the liberation of rwanda, Transatomic has obtained $ 6 million in fund, including $ 2 million from venture capital fast Founders Fund ( backers of Spotify, Airbnb, and SpaceX ). Dewan and Massie have used some of this semen money to set up a lab in Cambridge, Massachusetts, where, for the following three years, they will test materials for their future nuclear reactor under the extreme point conditions created by nuclear fission. But their road to an actual nuclear reactor will be a very long one .
Consider America ’ s relationship with nuclear world power. During the Cold War, the U.S. wanted to build a commercial nuclear exponent diligence before the Russians. The U.S. Navy already used light-water nuclear power on its submarines, providing an slowly blueprint to expand upon. The early and technically expedient decision to commercialize light-water reactors, “ locked the U.S., and the rest of the worldly concern, into one type of engineering, ” Dewan says .
All 99 U.S. commercial reactors in practice today are light-water reactors. That uniformity is not a trouble until something goes wrong—and then the entire nuclear industry gets tarred with the same brush. The meltdowns at Three Mile Island and Chernobyl turned an entire coevals away from nuclear ability. The meltdown at the Fukushima Daachi plant in 2011 deterred another, despite the fact that nuclear is easily scalable, carbon-free, base-load ability. “ When nuclear fails, it fails spectacularly, ” Massie says. “ And it gets a lot of coverage. ”
When I visit their offices in Cambridge, Dewan and Massie clutter up a whiteboard to show merely how safe and efficient their nuclear reactor will be. In light-water reactors, fuel rods packed with uranium pellets are submerged in water, which slows neutrons to a rush that induces fission in the uranium and heats the rods. The hot urine then powers a steam turbine that generates electricity. The system works well, except for two problems .
The first is that fission product poisons, like krypton and xenon, roll up in the rods. These gases consume neutrons, which ultimately stops the fission reaction. Every four years or thus the rods need replacing, even though 96 percentage of their energy remains untapped, rendering them highly radioactive pine away products that have to be stored in a secure location constantly. The other problem is the reactor ’ randomness changeless need for electric ability to pump cold water over the core, which holds the fuel rods. This water prevents it from overheating. Lose office, like at Fukushima, and the core melts down .

In dissolve salt reactors, uranium salt serves as the fuel. When heated above 500°C, the fuel strategic arms limitation talks changes from a solid to liquid state. It flows by zirconium hydride, which slows its neutrons and induces fission, generating heat. Because there are no rods to trap krypton and xenon, they are endlessly off-gassed. “ You basically simmer the nuclear reactor like a Crock-Pot for decades, ” Dewan says. “ That ’ s how we achieve a 96 percentage burn rate. We ’ re able to leave the uranium in and constantly remove the poisons that would differently shut it down. ” The fuel salt flows through a closed circuit with a drain that ’ sulfur blocked by a freeze plug, a ball of electrically cooled frozen strategic arms limitation talks. If the reactor loses electricity, the plug melts, and the fuel drains into a tank where it cools and solidifies .

“You basically simmer the reactor like a Crock-Pot for decades. That’s how we achieve a 96 percent burn rate.”

While the nuclear physics of molten salt reactors were proved at Oak Ridge 50 years ago, Dewan and Massie need to rigorously test the reactor ’ mho materials. Down the street from their Cambridge offices, Dewan shows me a lab where they ’ ll be exposing metals and ceramics—components that could be used in the nuclear reactor ’ second pipes, pumps, and valves—to salt and extreme heat using a furnace the size of a refrigerator. Their adjacent measure will be to design and build a 20-megawatt demonstration nuclear reactor that they hope to have run by 2020. Their ultimate finish is a 520-megawatt commercial reactor, which they say can be built for $ 1.7 billion­—half the cost of a light-water nuclear reactor. Despite the friendly economics, the U.S. Nuclear Regulatory Commission is not focused on license progress reactors. “ There ’ randomness no regulative framework that allows a developer to say, ‘ This is what we need to get approval, ’ ” says Lester. That, in turn, deters investment. “ Investors want to see a regulative pathway, ” Lester says. So companies like Bill Gates ’ mho TerraPower, which has developed a next-generation traveling-wave nuclear nuclear reactor, are looking to build abroad. massive energy needs and pollution problems have driven China to investigate many types of reactors—molten salt, sodium-cooled fast reactors, and high-temperature reactors. China may commission multiple models, since it plans to build 45 reactors over the following decade .
To Dewan, sending their engineering to China would be a miss opportunity. If the U.S. wants to lead the world in houseclean, safe nuclear energy again, she says, it urgently needs to broaden regulations. But there ’ s resistance from the coal and natural boast industries, which see nuclear energy as a bottom-line terror, and from some environ­mental groups that argue nuclear will always pose risks. But Dewan is undeterred. She doesn ’ metric ton want to build a mellow salt reactor in China. She wants to keep Transatomic ’ south operations in the U.S., where the promise of nuclear energy was born. “ It ’ second American engineering, ” she says. “ It ’ mho american engineers. We want this country to have the benefits of it first base. ”

How It Works

Molten Salt Reactor

  1. preferably than use solid fuel, a fade salt nuclear reactor heats uranium salt to more than 500°C, liquefying it .
  2. The liquid fuel flows past a moderator that slows down neutrons and induces fission, generating heat for steamer turbines .
  3. If a nuclear reactor loses might, a freeze ballyhoo melts, draining the radioactive fuel into a tank where it cools to a solid.

This article was in the first place published in the June 2015 topic of Popular Science as part of our “ New Faces Of Energy ” feature .

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