Deep beneath Finland’s bedrock lies one of humanity’s most ambitious engineering projects—a facility designed to hold radioactive waste for longer than civilization has existed. This episode explores how scientists and engineers are tackling the nearly impossible challenge of storing nuclear waste safely for tens of thousands of years. We look at the physics of radiation decay, the chemistry of corrosion-resistant materials, and the geologic stability needed to protect the waste from water and seismic activity.

Beyond the science, we confront the communication problem: how can we warn future generations about danger if languages and symbols evolve beyond recognition? The story of nuclear waste storage is as much about human foresight as it is about engineering. It forces us to think in timeframes that stretch beyond our species’ recorded memory, demanding a kind of long-term responsibility rarely seen in any other field.

From the tunnels of Onkalo to new storage concepts that use molten glass or deep boreholes, this episode examines the crossroads of technology, ethics, and time. What does it take to build something meant to last longer than humanity itself—and what does that say about the legacy we’re leaving behind?