The Race to Solve Nuclear Energy’s Biggest Problem

Nuclear energy is regaining momentum as nations worldwide seek to diversify their energy sources and lessen dependence on fossil fuels. However, a major hurdle persists in managing the waste generated by nuclear power plants. Three categories of nuclear waste exist: low-, intermediate-, and high-level radioactive waste. The majority of waste comprises lightly contaminated items like tools and clothing, with radioactivity levels around 1 percent.

High-level waste, primarily spent fuel, constitutes about 3 percent of the total waste but harbors 95 percent of the radioactivity. Nuclear facility operators bear the responsibility of safely disposing of all radioactive waste they generate. Though nuclear power plants produce minimal waste compared to other energy sources, it remains among the most challenging to manage effectively.

Nuclear fuel's high energy density implies that generating significant electricity necessitates only a small amount of fuel, resulting in limited waste production. For instance, an individual's annual energy requirements require just 5 grams of high-level waste. A conventional 1 GW nuclear plant, capable of powering over a million people, generates approximately three cubic meters of vitrified high-level waste per year.

The Nuclear Waste Management Organisation (NWMO) in Oakville, Canada, has established a test site for nuclear waste storage. This facility, situated within a warehouse, utilizes autonomous machines to stack 8,000 kg of bentonite clay blocks into a narrow rock tunnel and fill the gaps between them with crumbled clay. Each block encases a copper-coated steel container designed to hold spent nuclear fuel.

These blocks are subsequently sealed with additional clay and concrete in underground tunnels, allowing the radioactive material to decay over thousands of years without posing a risk to the public. The metal fuel containers are designed to endure the pressure of being buried beneath a 3-kilometer-thick glacier, should a future ice age occur before the radiation has fully decayed.

They have also been successfully tested for resistance to crushing forces equivalent to being over 6 kilometers underwater. The NWMO team aims to construct the final site 1,600 kilometers northwest of the test facility, in Ignace, 750 meters below the hard rock of the Canadian Shield. Once completed, around 2040, it is projected to store nearly 6 million bundles of spent fuel generated by Canada's four nuclear power plants throughout their operational lifetimes.

Similar sites are under development in other countries, including Finland, Sweden, and Japan. While scientists have addressed numerous technical challenges associated with developing deep geological repositories over the years, making them a viable option for nuclear waste storage, securing political and public support for these facilities remains challenging due to concerns about contamination.

In the United States, the government began investigating potential deep geological repository sites in the 1980s, but progress has lagged due to extensive local opposition. The Yucca Mountain in northern Nevada was initially selected as the location for the development of the country's first geological repository, having submitted the first license application for such a site.

However, concerns about the nearby active volcano, the location's placement in an active earthquake zone, and the proximity to the water table have led to widespread opposition. The Department of Energy (DoE) subsequently shifted its focus to other potential sites, including Utah, Idaho, Louisiana, Oklahoma, and Tennessee, but Yucca Mountain remains the only legally designated site for permanent storage at present.

The United States has amassed approximately 95,000 metric tonnes of nuclear waste over the years, necessitating proper management. Several deep geological repositories are expected to begin operation in various countries over the coming decades. Meanwhile, scientists are exploring alternative waste management solutions. As multiple governments explore the potential to develop nuclear power capacity, they must also address the waste problem and construct safe disposal facilities alongside new nuclear power projects.