January 29, 2024

Thorium will solve the nuclear problem (or at least this startup thinks so)

Swiss startup Transmutex has just raised a $23m Series A extension round

Freya Pratty

2 min read

Nuclear power has long divided European opinion. On one side of the fence there are the people who think it’s a vital part of the sustainable energy mix — on the other are those who question its safety.

Many European startups are working on nuclear fusion — a holy grail reaction that could give humanity access to infinite power (but which may be many, many years off). At the same time, other startups are working on upping the safety of the form we have in use today: nuclear fission.

One of those is Swiss startup Transmutex, which has just raised a $23m Series A extension round co-led by Union Square Ventures and Steel Atlas, with participation from At One Ventures.


Transmutex was cofounded in 2019 by scientists from CERN, the European Organization for Nuclear Research, in Geneva — where the startup is now based. 

Enter thorium

Nuclear power stations create heat by splitting atoms — typically neutrons colliding with uranium, which then releases more neutrons, producing a chain reaction. The heat that this generates is used to create electricity. 

Transmutex is building a nuclear reactor which uses thorium — a lead-like metal that is “mildly radioactive”, according to cofounder and CEO Franklin Servan-Schreiber — as a feedstock rather than uranium. 

Thorium’s advantages over uranium are numerous, he says. “It’s three times more prevalent than uranium, it burns much better and, if you do it the right way, it doesn’t produce long-lived waste.”

Transmutex’s reactor also includes a particle accelerator, which means the reaction can be stopped within two milliseconds.

“It’s a reactor design that is guaranteed to be safe and that can reduce the radiotoxicity of long-lived waste from 300k years down to 300 years,” says Albert Wenger, managing partner at Union Square Ventures, which led Transmutex’s Series A round.

Sourcing thorium

“Thorium is everywhere in the Earth’s crust,” says Servan-Schreiber. It’s particularly easy to source from the areas around coal plants or from mines, where the crust has already been disturbed.

Uranium, on the other hand, is increasingly sought after and therefore hard to source. Following a wave of renewed interest in nuclear energy in the US, Europe and Asia, the price of uranium has soared to record levels and concerns about the supply chain are mounting. 

Servan-Schreiber says there’s particular interest around thorium in India, because the country has realised it won’t have enough uranium to produce the amount of nuclear energy it's planning to. 

Transmutex is now working on finalising agreements with several governments to build reactors — in Europe and in Asia. After that, the company hopes to begin planning and construction within two to three years.


Freya Pratty

Freya Pratty is a senior reporter at Sifted. She covers climate tech, writes our weekly Climate Tech newsletter and works on investigations. Follow her on X and LinkedIn