7 Best Nuclear Reactor Startups to Watch in 2025

The Definitive Seedtable Ranking of Nuclear Reactor Startups

We track 71,000+ companies and rank them dynamically using our Seedtable Score – a score that uses quantitative and qualitative data points to signal the momentum behind a company. We then monitor the list manually leveraging our expertise as founders and investors.

There are 7 start-ups with an aggregate funding of $109.4m. The average funding per company in this subset is $15.6m.

Last update to the database: Feb 18, 2025. See changelog.

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LeadCold logo

LeadCold

LeadCold is a company developing lead-cooled small nuclear reactor technology founded in 2013 by Janne Wallenius, Jesper Ejenstam and Peter Szakalos.

2

Funding Rounds

$21.1m

Money raised

Terrestrial Energy logo

Terrestrial Energy

Terrestrial Energy is developing molten salt nuclear reactors.

5

Funding Rounds

$40.7m

Money raised

Gen4 Energy logo

Gen4 Energy

A company that was developing an advanced technology mini nuclear reactor, based on intellectual property developed by scientists at Los Alamos National Laboratory. It was located in Denver, Colorado.

2

Funding Rounds

$12.9m

Money raised

Moltex Energy logo

Moltex Energy

A nuclear energy company making a stable salt reactor.

1

Funding Rounds

$7.5m

Money raised

Transatomic Power logo

Transatomic Power

A nuclear reactor design company developing Waste-Annihilating Molten Salt Reactor. The company ceased operations in September 2018.

1

Funding Rounds

$763.0k

Money raised

Copenhagen Atomics logo

Copenhagen Atomics

A company developing nuclear reactors with molten salt as coolant and thorium as fuel.

1

Funding Rounds

$21.0m

Money raised

Astral Systems logo

Astral Systems

Manufacturer of compact nuclear fusion reactors to produce medical isotopes on-demand for diagnostic and therapeutic applications in healthcare.

1

Funding Rounds

$5.5m

Money raised