Two billion years ago, Earth ran a nuclear reactor. No humans. No startups. And it shut itself off on its own.
My AI research agent pulled the receipts - Oklo in Gabon was a natural fission reactor that pulsed like a kettle: about 30 minutes on, roughly 2.5 hours off. Groundwater was the control rod. Water seeped in, slowed the neutrons, fission lit up, heat boiled the water away, reaction paused, rock cooled, water returned, repeat. Back then uranium had more of the spicy isotope - about 3 percent vs under 1 percent today - so nature had the right ingredients. Each zone made around 100 kilowatts. There were about 15 at Oklo and one more at Bangombé. This stop-start dance ran for hundreds of thousands of years.
Why should you care in 2026? Because Finland is about to do the thing everyone argues about and almost no one ships: permanent nuclear waste disposal. Onkalo finished full-system trials and is set to start burying spent fuel in the mid-2020s. Their recipe is simple to explain and hard to execute - copper canisters, clay, deep rock. Oklo is the deep-time sanity check. In many cases, the fission leftovers barely moved in two billion years. You cannot run a 100,000-year lab test. Nature already did one.
Now the catch. Oklo is not your repository. Its rock chemistry, water, and ore geometry were weird and perfect. Some elements travel more than others. Modern repositories are engineered barriers in stable rock, not uranium ore bodies. Oklo is a strong analogue, not a blank check. Also, do not confuse the ancient site with the US startup named Oklo - different thing.
Zoom out. While fusion keeps winning lab trophies, fission is the adult in the room. A new US reactor finally came online last year, and grids that run on vibes and sunny days still need heavy, steady power. If we want clean power without magical thinking, we build more nuclear and we finish the waste job. Ambitious and careful beats timid and dirty. Every time. ⚡🪨
Question for you - if Finland starts burying fuel this year, does Oklo tip you toward yes on nuclear, or what would it take?