Japan’s Fukushima nuclear power plant has started releasing treated radioactive water, from the damaged nuclear plant hit by a devastating earthquake and tsunami in 2011, into the ocean. The move has stirred up conversation around a question that scientists and governments have been struggling to answer for decades: how to manage nuclear waste?
Nuclear energy is one of many alternatives to carbon-based power on the path of climate change mitigation. Currently, 10% of the world’s electricity comes from nuclear energy. Aiming for net-zero emissions, many countries are mulling a higher contribution from nuclear as a way to transition to clean energy. The U.S., Switzerland, Spain, Sweden, and Finland are all planning to build new or update existing nuclear reactors, while India, China, and Russia are working on expanding their nuclear power projects.
However, using nuclear energy comes with its own challenges – one of the biggest being how the facility will be able to store and dispose of nuclear waste in a safe and controlled manner.
Experts are aware of many options on this front but they are all temporary. A more permanent solution is required because the waste can persist in a dangerous state for periods ranging from days to decades, depending on the isotope.
The temporary options include storing spent fuel in pools until they cool and in dry casks and burying them in near-surface disposal facilities at ground level or below. These facilities typically have a protective covering at least a few metres thick. The waste is placed in vaults and then backfilled with soil and clay. The volume is then covered with an impermeable material followed by topsoil.
These facilities are usually used for low-level and intermediate-level waste – i.e. which has such levels of radioactivity, typically coming from an operating plant.
High-level waste has few options; the most feasible is deep geological disposal, and Finland seems to be showing the way. A facility in this Scandinavian country will become the first to realise this disposal option when the Onkalo repository opens in 2025.
The project started in 2000 and will use the Swedish KBS-3 concept, which proposes three layers of protection: the waste is placed in copper canisters, wrapped in bentonite clay, and buried more than 400 metres below ancient bedrock. The repository, built by Finnish company Posiva, will also employ safety steps called release barriers to keep the waste isolated from its surroundings.
Finland’s long-term plan is to leave the waste undisturbed for 100 millennia. It will also study how the site might change and how the safety measures evolve. The facility has already tested the site to check if the tunnels where the waste is stored will be able to weather geological changes like an ice age or earthquakes.
Posiva expects the facility will need 100-120 years to become full.
