TerraPower is an American nuclear reactor design and development engineering company headquartered in Bellevue, Washington.

[1] TWR places a small core of enriched fuel in the center of a much larger mass of non-fissile material, in this case depleted uranium.

[4] However, in January 2019 it was announced that the project had been abandoned due to technology transfer limitations placed by the Trump administration.

[5] In October 2020, the company was chosen by the United States Department of Energy as a recipient of a matching grant totaling between $400 million and $4 billion over the ensuing 5 to 7 years to build a demonstration reactor using their "Natrium" design.

In December 2011 India's Reliance Industries bought a minority stake through one of its subsidiaries and its Chairman Mukesh Ambani joined the board.

Other TerraPower participants include[8] scientists and engineers from Lawrence Livermore National Laboratory, the Fast Flux Test Facility, Microsoft, and various universities, as well as managers from Siemens, Areva NP, the ITER project, Ango Systems Corporation, and DOE.

TerraPower selected Kemmerer, Wyoming as the site for a 345 MWe Natrium reactor using a molten salt energy storage system.

[11] Company objectives include:[12] TerraPower chose traveling wave reactors (TWRs) as its primary technology.

Their major benefit is high fuel utilization that does not require nuclear reprocessing and could eliminate the need to enrich uranium.

On November 6, 2009, TerraPower executives and Bill Gates visited Toshiba's Yokohama and Keihin Factories in Japan, and concluded a non-disclosure agreement with them on December 1.

[23][24] In February 2022, it was announced that the two companies had agreed to build a demonstration fast-spectrum salt reactor at Idaho National Laboratory (INL).

Whilst this metallic fuel has a melting point much lower than the ceramic pellets used in light water reactors it also has higher heat conduction.

[28] In June 2021, TerraPower and PacifiCorp (a subsidiary of Warren Buffett's Berkshire Hathaway Energy) announced plans to build a joint Natrium reactor.