Navigating nuclear past: The future of radioactive waste disposal

What happens to a nuclear-powered ship when it becomes obsolete, usually after several decades of service? The United States developed a special procedure, the Ship-Submarine Recycling Program (SRP), for the safe dismantling of nuclear-powered vessels.

Over 100 American nuclear submarines have undergone the dismantling process, as well as, in the past, nuclear cruisers, and currently the aircraft carrier ex-Enterprise. Decommissioned ships keep their names during dismantling, with the prefix "ex-". Likely in 2026, the first Nimitz-class aircraft carrier, USS Nimitz, will also be scrapped, possibly on its final voyage with the US Navy.

While the hull is dismantled like any other vessel, nuclear-powered ships must first be stripped of nuclear fuel, followed by the removal of reactor modules.

The fuel is transported to the Naval Reactors Facility in Idaho, and the propulsion elements are carried by train to the Hanford site in Washington state, where they end up in a nuclear dumpsite known as Trench 94.

To ensure the safe transport of potentially dangerous ship parts, a special train system named Atlas was built. The 16-axle platform, approved for travel on standard railway tracks, can transport loads exceeding 200 metric tonnes, monitoring radiation levels along the entire route.

Atlas faces a significant challenge, as the U.S. Department of Energy estimates that by 2060, it will need to transport up to 140,000 metric tonnes of spent nuclear fuel and radioactive materials. Where should such vast quantities of hazardous waste be stored?

For nearly 70 years, various countries facing this challenge have been striving to find optimal solutions.

For years, the largest producers of radioactive waste managed their problem by dumping it into the sea. Hundreds of thousands of metric tonnes of waste from the United States, the UK, Switzerland, and France were sunk in various waters, and this practice was banned only in 1993.

The Soviet Union also disposed of significant amounts of waste by sinking not just containers, but entire ships filled with waste and reactors containing fuel or – as in the case of the K-27 submarine – an entire vessel with a complete nuclear power plant.

The scale of this operation was so dangerous that the West (including Germany and Norway) funded the construction of a storage facility for Russia in the Saida Bay (Sajda Guba) near Murmansk. The facility, opened in 2008, was presented by Russian propaganda as a success for the Putin administration.

The agreement that allowed the funding countries to oversee the proper securing of waste was terminated by Russia in November 2024.

Ultimately, these actions are merely temporary measures. The safe and long-term storage of waste, which may remain hazardous for thousands of years, is expected to be addressed by deep geological repositories. These underground storage facilities are located in appropriately stable geological structures, with no risk of underground water circulation. Radioactive waste is sent there for long-term – from a contemporary human perspective, eternal – storage.

Currently, several such facilities are operating or under construction worldwide, intending to store radioactive waste at notable depths – usually several hundred metres.

Examples of such repositories include the Swedish Äspö Hard Rock Laboratory, the Belgian HADES Underground Research Facility, and the Finnish Onkalo (Finnish for "hidden place"). Japan is constructing the deepest repository – the Mizunami Underground Research Lab – aiming to store its waste in granite shafts at a depth of 1,000 metres.

Constructing and planning such facilities presents a significant challenge, not only to ensure their immediate security but also to mark them so that future generations can understand the dangers within, even in 1,000 or 10,000 years.

The challenge is greater given the uncertainty about what language future explorers will speak, which cultural codes they will be familiar with, and what their level of technological development will be. If not adequately warned, they might breach these sites – much like past explorers entered ancient ruins without any knowledge of their contents or builders' language or symbols.

This is why the Americans, planning the security of the Waste Isolation Pilot Plant (WIPP), established a group called the Human Interference Task Force, comprising engineers, anthropologists, nuclear physicists, and behavioural scientists. Their task was to develop a method for preserving knowledge about hazardous waste over millennia.

Some ideas included creating a "nuclear monastic order" which, similar to religious beliefs, would perpetuate the fear of the repository through the ages. Stanisław Lem, who was invited to contribute, proposed cultivating genetically modified plants that would grow only in contaminated areas.

French philosophers offered an imaginative suggestion, proposing the use of cats as carriers of warnings. They assumed these animals would continue to accompany humans in the future, as they have for millennia. The cats would be genetically modified to change colour in response to radiation. The fear of locations where cats change colour would be ingrained in culture through stories or songs.

The task of developing warnings to protect future explorers from unknowingly entering WIPP has been entrusted to the Department of Energy, which is working on a marking system called Passive Institutional Controls.

In addition to graphical information, the markings will include above- and underground installations with information, various markers, granite pillars forming the above-ground outline of the repository, and metal elements indicating the location of underground stores.

Additional information, provided in multiple languages, is to be stored in archives scattered globally – all to minimise the risk that knowledge of the hazardous waste might be forgotten for some reason in the future. This multifaceted marking system is expected to be ready by 2033.