TerraPower’s Natrium pairs a sodium fast reactor with heat storage

September 2, 2020, 3:00PMNuclear News

An artist’s rendering of Natrium. Image: TerraPower

The Natrium reactor and energy system architecture, recently introduced by TerraPower and GE Hitachi Nuclear Energy (GEH), offers baseload electricity output from a 345-MWe sodium fast reactor with the load-following flexibility of molten salt thermal storage. Stored heat can be used to boost the system’s output to 500 MWe for more than five and a half hours when needed, according to TerraPower. A company representative told Nuclear News that the company expects a commercial Natrium plant to cost $1 billion or less.

What they’re saying: “TerraPower values collaboration with GE Hitachi to make nuclear generation as affordable as possible,” said Chris Levesque, TerraPower’s president and chief executive officer. “Our exceptional technology development capabilities, unmatched financing credibility, and achievable funding strategy mean that the Natrium technology will be available in the late 2020s, making it one of the first commercial advanced nuclear technologies.”

Jay Wileman, GEH president and CEO, said, “We designed this system with operator input to potentially increase their revenues by 20 percent through the use of energy storage.”

Natrium, which gets its name from the Latin for sodium, is designed to integrate into power grids with high penetrations of renewables, follow the daily electric load, and take advantage of peaking prices. The molten salt thermal storage technology that makes it possible is already in use at utility-scale solar thermal plants.

Design essentials: Both TerraPower and GEH have experience designing and developing sodium fast reactors. “The Natrium system combines molten salt energy storage with the best of the Traveling Wave Reactor and PRISM technologies, along with additional innovations and improvements,” according to TerraPower. “The team has dramatically improved plant performance and economics, resulting in a sodium fast reactor that competes economically in the U.S. and other countries.”

Nonnuclear mechanical, electrical, and other equipment would be housed at a distance from the reactor and in separate structures that could be built to industrial standards rather than nuclear standards, reducing costs. The design would reduce the amount of nuclear-grade concrete by 80 percent compared to large reactors, according to TerraPower.

Heat transport: To get the reactor’s heat to energy storage and electricity generation, Natrium makes use of three heat transport fluids: liquid metal sodium, molten nitrate salt, and water. According to TerraPower, in the primary system the sodium-cooled nuclear core produces heat that is transferred to the molten salt through a heat exchanger. The molten salt flows from the nuclear island to the energy island where the hot salt may be stored or directly supplied to the steam generation system. The steam generation system then produces high-pressure, superheated steam that the turbine/generator converts to electrical power.

Advanced Reactor Demonstration Program: TerraPower, GE Hitachi, and Bechtel have submitted a proposal based on Natrium technology for the Department of Energy’s Advanced Reactor Demonstration Program (ARDP).

“For the ARDP proposal, Bechtel adds current and unmatched experience managing and executing large nuclear projects, and the team’s utility partners bring operating capabilities alongside a market demand for utility-scale advanced nuclear technologies,” TerraPower’s representative told NN.

According to the company, Energy Northwest and Duke Energy have both expressed their support for the commercialization of Natrium through the ARDP. The project also has the backing of PacifiCorp, a subsidiary of Berkshire Hathaway Energy. TerraPower’s founders include Bill Gates, who serves as chairman of the board.

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