Hoping to revive the moribund U.S. nuclear energy business, the Department of Energy (DOE) announced this week it will help build two radically new nuclear reactors inside 7 years. Funded by DOE’s new Advanced Reactor Demonstration Program, the designs embody unique options equivalent to cooling by sodium or helium as a substitute of water in a bid to be safer and extra economical than typical energy reactors.
DOE officers “had been attempting to do one thing new and push the know-how ahead but in addition to remain inside that 7-year time-frame,” says Ashley Finan, a nuclear engineer and director of the Nationwide Reactor Innovation Middle at Idaho Nationwide Laboratory who was not concerned within the selection. “I feel these two [designs] had been judged to be prepared for demonstration.”
DOE will cut up the entire price of constructing every plant with personal business. Every mission receives $80 million this yr and will obtain a complete of between $400 million and $four billion in funding over the subsequent 5 to 7 years. The company additionally intends to make extra, smaller awards this yr for much less mature concepts, Finan says. A committee of consultants whose roster has not been revealed chosen from a number of designs, she says.
The 2 profitable designs deviate basically from a traditional energy reactor, which is basically a boiler. Inside the core of a nuclear reactor, atoms of uranium gas cut up in a series response, releasing power and free-flying neutrons, which then cut up different uranium atoms. In a traditional energy reactor, the power heats extremely pressurized “cooling” water that circulates by the core. Nonetheless below stress, the cooling water flows to an exterior steam generator, the place it boils water in a separate circuit, producing steam that drives generators to generate electrical energy.
As a substitute of water, the 345 megawatt Natrium reactor from TerraPower, Inc., and GE Hitachi would use molten sodium metallic as a coolant. As a result of sodium has a a lot larger boiling temperature than water, the coolant wouldn’t need to be pressurized, decreasing the plant’s complexity and price. The sodium would switch its warmth to molten salt, which might then movement on to a steam generator or to a storage tank, to be held to generate steam and electrical energy later. In distinction to a traditional nuclear energy plant, the Natrium plant might shortly ratchet up or down its whole output whilst its reactor continues to run steadily and effectively. That would complement renewable sources equivalent to wind and photo voltaic power, which produce fluctuating energy ranges that must be evened out.
In distinction, the Xe-100 design from X-Vitality would use pressurized helium fuel to chill its uranium-based gas. That gas can be packaged not within the typical metal-clad rods, however in “pebbles”—spheres of graphite infused with numerous ceramic kernels that include the uranium. Like a large gumball machine, the reactor would maintain 220,000 pebbles, which might slowly descend by the core and, as their gas was spent, would exit from a port on the backside. Heated to 750°C, the helium would generate steam in a secondary circuit to provide electrical energy. In precept, the pebbles can’t soften, eliminating the chance of a meltdown. Every Xe-100 would generate 80 megawatts, and a plant would consist of 4 of the modular reactors.
Each crops needs to be less complicated and cheaper than typical nuclear energy crops. As a result of Natrium sodium coolant is unpressurized, the reactor requires a smaller containment construction than a traditional reactor. The plant additionally “decouples” the reactor and the electrical energy producing parts of the power, which sit on reverse sides of the storage tanks. These options ought to permit engineers to cut back use of high-priced bolstered concrete by 80%, says Tara Neider, a TerraPower engineer and mission director for the Natrium design. “Natrium is all about making a nuclear plant less complicated so it may be extra environment friendly,” she says. Each corporations say they’ve but to decide on websites for his or her reactors.
Each reactors would additionally depart from typical designs in utilizing a gas that’s extra extremely enriched in uranium-235, the fissile isotope that’s key to producing a series response. To attenuate the chance that the gas, recent or spent, might be diverted to create a nuclear weapon, water-cooled energy reactors run on gas that it’s 3.5% uranium-235. The Natrium and Xe-100 reactors would use gas enriched to 20%, which might allow them to run longer on a batch of gas and extract extra power from it. Such gas isn’t presently produced in the USA, however present producers might make it comparatively simply, Finan says. The gas would even be tough to divert to weapons, she says, partially as a result of it will require fewer refueling stops.
As in lots of issues nuclear, what’s outdated is new: For the reason that start of the nuclear age within the 1950s, engineers have constructed a handful of sodium-cooled reactors and even a few pebble-bed reactors. However the satan is within the design particulars, and each TerraPower and X-Vitality goal to make reactors which are secure and might compete with cheaper types of energy. Finally, TerraPower hopes to market a Natrium plant for lower than $1 billion, Neider says.
This yr, DOE plans to make between two and 5 extra awards for superior reactor designs which are even more energizing, Finan says. “DOE needs to offer a pathway ahead for these applied sciences that might properly be game-changers however are usually not fairly prepared for demonstration,” she says. Every “threat discount” award would include $30 million this yr and as much as $400 million whole over 7 years.
For U.S. nuclear engineers, the prospect of constructing new superior reactors is thrilling, after greater than 2 many years throughout which the USA commissioned only one new energy reactor. “That is what we’ve been working for all alongside,” Neider says. “It’s thrilling occasions.” However that shiny future will depend upon continued funding by Congress and help from what is perhaps a brand new presidential administration. And, in the end, builders need to show that nuclear can compete economically with different types of energy.