The first facility for safe disposal of spent fuel
In depth

The first facility for safe disposal of spent fuel

The first deep geological disposal facility to isolate radioactive waste is being built in the Finnish town of Olkiluoto. Sweden and other countries are also taking the necessary steps to build similar sites.

The first deep geological disposal facility to isolate radioactive waste is being built in the Finnish town of Olkiluoto

Deep geological final disposal

Intense research has made it possible to determine the suitability of different types of rock to enclose deep geological final disposal facilities to isolate radioactive waste. These sites are built in the right geological formations, several hundreds meter deep. They are designed in such a way that they can contain high-level waste (such as spent fuel) for hundreds of thousands of years.

A fundamental characteristic of deep geological  disposal facilities is passive safety, meaning that once the disposal facility has been close no further human action is required.

Building these facilities several hundred meters below ground level—at a depth that effectively isolates waste from potential surface perturbations for hundreds of thousands of years—involves placing the waste in a non-dinamic environment, as opposed to a more dynamic near-surface geological environment where conditions tend to be less stable.

Spent fuel and storage period

After spent fuel is removed from nuclear power reactors it continues to generate significant heat for several years. To cool it down, it is first deposited in water pools or in dry storage. Both sites guarantee the integrity of the spent fuel. They avoid the emission of radiation or radioactive materials and protect people and the environment. Spent fuel, however, remains highly radioactive for several thousand years and it must be isolated during this time.

Once the heat has been reduced, spent fuel can be stored in storage facilities in artificial structures, several hundred meters deep. This is known as deep geological disposal facilities. The goal is to contain the radioactivity of the fuel by encapsulating it into corrosion-resistant canisters and embedding the caniseters in swelling clay inside the reposistory’s tunnels, up to 500 meters below ground level.

Sweden-Finland cooperation

Up until 1996, Finland transported the spent fuel from the Loviisa nuclear power plant to the Soviet Union, and later to Russia, for reprocessing. When the Finnish government issued the operating license for the Olkiluoto nuclear power plant in 1987, it requested that the licensee develop a radioactive waste management plan, including spent nuclear fuel, which had to be permanently stored in Finland.

In Sweden, power plant owners came together in the late 1970s to form the SKB, in order to jointly manage spent fuel. This initiated research and development activities for the development of a final disposal concpt, which led to the KBS-3.

Finland issued this license in 2015, marking the first time a construction license for a geological disposal facility

The first disposal facility in Finland

Before construction of a deep geological disposal facility can begin, the company in charge of implementing the concept needs to obtain a construction license. Finland issued this license in 2015, marking the first time a construction license for a geological disposal facility was received anywhere in the world.

The site was chosen following the evaluation of a series of options for several years. Once different possibilities were analyzed from geological data, Posiva continued site characterization through site-specific studies, which included drilling, to fine a geologically suitable environment. During this process Posiva also started discussions with several municipalities regarding the possibility of hosting a facility with these characteristics.

“Social acceptance and social factors play a crucial role in site selection”, said Jussi Heinonen, Director of the Nuclear Waste Regulation and Safeguards Department at Finland’s Radiation and Nuclear Safety Authority (STUK). “Social acceptance relates to trust for the implementer, regulator and decision makers. This trust has to be built and maintained“, indicates Heinonen.

Posiva is in the middle of the construction of the ONKALO disposal facility, at a depth of over 400 meters below ground level. The disposal process is planned to start in 2024.

The ONKALO facility under construction (Source: Posiva Oy)
The ONKALO facility under construction (Source: Posiva Oy)

Progress in other countries

En 2011, the SKB presented its license application for the construction of a disposal facility in Forsmark, north of Stockholm, which was reviewed by the Swedish Radiation Safety Authority (SSM) and the Land and Environmental Court.

In other countries such as France, the National Radioactive Waste Management Agency (ANDRA) is currently preparing its license application. In Canada and Switzerland, national waste management agencies are investigating appropriate sites through site characterization.

Source: International Atomic Energy Agency