New 'fast breeder' nuclear reactor hits critical milestone in transition from uranium to thorium

India may have just taken a major step toward reshaping the future of energy, according to Interesting Engineering.

In a post on the social platform X, Prime Minister Narendra Modi announced that the country's long-anticipated Prototype Fast Breeder Reactor has achieved "criticality," a key milestone meaning it can now sustain a controlled nuclear chain reaction.

"Today, India takes a defining step in its civil nuclear journey, advancing the second stage of its nuclear programme," Modi wrote. "... It is a decisive step towards harnessing our vast thorium reserves in the third stage of the programme."

At its core, nuclear fission, the process of splitting atoms to release energy, can generate large amounts of electricity with far less pollution than gas or coal. That matters because reducing air pollution is linked to better respiratory health and fewer pollution-related illnesses.

The reactor is designed to produce more fuel than it consumes. Known as a "fast breeder" reactor, it can convert materials such as uranium 238 and plutonium 239 into usable fuel while operating, a capability that could extend fuel supplies and potentially lower long-term energy costs.

Perhaps more significant is India's push toward thorium, a more abundant element than uranium. By tapping into its large thorium reserves, the country could strengthen its energy security while reducing reliance on imported fuel.

Still, reaching criticality is only the beginning. The reactor will now undergo extensive testing and calibration before it can begin generating electricity for homes.

If successful, the technology could provide a stable, low-carbon-pollution energy source to complement renewables like wind and solar.

That said, nuclear energy comes with challenges. Managing radioactive waste remains complex, and experts stress that advanced reactor technologies must be deployed carefully to ensure safety and maintain public trust.

The milestone sparked excitement on social media.

Which of these savings plans for rooftop solar panels would be most appealing for you? Save $1,000 this year 💸 Save less this year but $20k in 10 years 💰 Save less in 10 years but $80k in 20 years 🤑 Couldn't pay me to go solar 😒 Click your choice to see results and earn rewards to spend on home upgrades.

"Massive respect to the scientists and engineers who pulled off this incredibly complex indigenous feat," one commenter wrote.

"This is what self-determination looks like in the 21st century. Even I am proud of India from afar," another added.

"Great achievement," a third commented. "This is what technology sovereignty looks like. We did this despite all the restrictions imposed on us."

Get TCD's free newsletters for easy tips to save more, waste less, and make smarter choices — and earn up to $5,000 toward clean upgrades in TCD's exclusive Rewards Club.