Finland's Onkalo Deep Geological Repository and the Global Challenge of Nuclear Waste Disposal

BBC Inside Science explores the enduring challenge of nuclear waste disposal, explaining why some radioactive isotopes remain hazardous for tens of thousands to millions of years. The episode centers on Finland's Onkalo repository as a real-world example of deep geological storage, detailing how spent nuclear fuel will be buried in bedrock, surrounded by bentonite clay, and sealed to prevent future exposure. Alongside the engineering, the program delves into the science behind why geological disposal is favored, the role of natural analogues like Oklo in understanding long-term behavior, and the global policy landscape. It also touches on philosophical and artistic approaches to communicating risk to future civilizations. The show features scientists and commentators who illuminate both the practicalities and the imaginative questions raised by burying hazardous waste for millennia.

Understanding Nuclear Waste and Time Scales

In the opening sections, the program lays out the core problem: nuclear fission within reactors transforms uranium into a range of radioactive byproducts. These isotopes decay over time, some with half-lives measured in seconds, others stretching toward hundreds of thousands or millions of years. The discussion emphasizes that the waste remains hazardous long after removal from the reactor, necessitating a disposal strategy that can function across scales that dwarf human history. The interview with Claire Corkhill anchors this segment, offering a clear explanation of why very long isolation times are required and how scientists compare different disposal timelines, from tens of thousands to a million years.

“Geological disposal is really the best thing to do with this material, and I personally like to call it the least worst option.” - Claire Corkhill

The Science of Waste: What Makes It Hazardous

Listeners are guided through the nature of spent nuclear fuel, the types of radioactive atoms produced when uranium splits, and how their decay releases radioactivity that can harm living tissue. The program differentiates between short-lived isotopes and those with long half-lives, underscoring why containment must endure across timescales that extend far beyond the lifespan of civilizations. The conversation clarifies the concept of a “half-life” and why it matters for designing containment systems that can outlive us by orders of magnitude.

Another crucial point is the choice of a disposal method. The guests discuss options historically proposed (space burial, deep-sea disposal) and why geological disposal has emerged as the preferred route. The idea is to keep the waste out of reach and out of contact with future populations and ecosystems for as long as it remains hazardous.

Geological Disposal and Natural Analogues

The narrative then connects theory to evidence by discussing natural analogues, notably the Oklo natural reactor in Gabon. Studying Oklo provides a way to observe how fission products migrate in the deep geosphere over geological timescales. The takeaway is that, in stable geological formations, fission products tend to stay close to where the fuel resided, which gives scientists confidence in the predictability of deep geological disposal models. The episode uses these analogues to support the argument that placing radioactive waste underground can be reliable when the geology is well understood.

“We can look to natural analogues. For example, there’s a natural uranium ore body in Oklo in Gabon, which shows that the fission products traveled only a centimetres over long times.” - Claire Corkhill

Finland’s Onkalo: A Real-World Repository

The central focus shifts to Onkalo, the world’s first deep geological disposal facility for spent nuclear fuel. The reporters and experts describe the drive northwest from Helsinki, the granite bedrock, and the 400-meter descent to the tunnels where deposition will occur. Onkalo’s design features deposition tunnels carved deep into bedrock, with each canister of spent fuel shielded in copper or multi-layer containment and surrounded by bentonite clay. The tunnels are then filled and plugged to maintain isolation from the environment for hundreds of thousands of years. The dialogue highlights that Onkalo represents a tangible milestone in the nuclear sector, a demonstration that long-lived, hazardous waste can be stored securely in a stable geological formation.

“It is a watershed moment in reality for the nuclear sector.” - Fiona McEvoy

Engineering, Rock, and Time: How It Works

The hosts relay the technical details provided by geologists and engineers: the bedrock’s stability, the use of bentonite clay to seal deposition holes, layered shielding, and the long-term monitoring plans. They discuss the role of the surrounding geology, how predictability over millions of years underpins safety, and why scientists view the deep geosphere as a more reliable containment environment than surface-based solutions. The Finnish site is described as relatively simple and well-suited to demonstrating the approach before expanding to more complex waste types in other countries.

“We know what our bedrock is like and what kind of waste we have, and we know what we need to do to keep the waste isolated.” - Claire Corkhill

Global Landscape: Who Is Ahead and What Lies Ahead

The program broadens to the international stage, outlining which countries have sites selected, which are permitting, and which are still at policy stages. Sweden, France, Switzerland, and China are named as leaders with imminent developments in similar rock types or disposal concepts. The United Kingdom and Japan are described as still at policy or site-search stages, with the Netherlands choosing an aboveground approach for now. The discussion emphasizes that Finland’s straightforward geological context and focus on a single waste type give it a unique advantage in pioneering the model, while other nations must navigate more complex mixtures of waste forms, geological conditions, and regulatory frameworks.

Throughout, the episode stresses that the Onkalo example is as much about governance, site selection, and social acceptability as it is about rock mechanics and materials science. The project’s lessons are framed as globally relevant, potentially guiding future repositories and informing policy decisions elsewhere.

Nuclear Semiotics, Culture, and Warning Future Generations

In a later section, the conversation turns to the non-engineering challenges: how to prevent future civilizations from disturbing the buried waste. Experts discuss various strategies—from masking structures in the landscape to creating narratives, myths, or “nuclear semiotics” that persist across generations. The discussion ranges from ceremonial or architectural approaches to more imaginative ideas, including art projects and even speculative “priesthood” or legend-building frameworks designed to deter curiosity long after today’s technologies are forgotten. The participants acknowledge the difficulty and uncertainty of communicating across millennia, but they explore a spectrum of possibilities that blend science, culture, and art.

“One of the most durable ways of telling our descendants not to go there is to create some kind of nuclear religion or myth.” - Gair Dunlop

Recap of the Recap: Creative Concepts and Open Questions

The discussion closes by acknowledging a wide array of ideas—from the practical engineering of repositories to the more speculative futures of cultural memory and post-human archaeology. The podcast acknowledges that the problem will outlive current civilizations, and that researchers continue to evaluate how best to communicate risk without presuming universal long-term comprehension. The exchange highlights ongoing work like the Nuclear Culture Research Group and related art-science collaborations exploring the ethics, philosophy, and culture of nuclear waste disposal.

In sum, the episode offers a comprehensive look at why deep geological disposal is chosen, how a real facility operates, and how cultures might safeguard future generations from buried hazards through a combination of science, design, and storytelling.

For listeners who want to engage further, the program invites correspondence about novel approaches to nuclear waste and calls for continued dialogue among scientists, policymakers, and communities who will inherit the decisions of today.