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What happens to nuclear waste?

The 452 nuclear reactors in operation worldwide generate 10,3 % of the world's electricity and produce few greenhouse gas emissions. On the other hand, this energy creates a large amount of more or less dangerous waste. In Europe alone (excluding Russia and Slovakia), the 142 reactors in operation produce about 6,6 millions m³ of waste during their operating life. What happens to it afterwards?

“Nuclear waste is classified according to the intensity of radiation and the time needed for its radioactivity to decrease”, explains Dominique Richit, Managing Director of Veolia Nuclear Solutions, which specialises in the dismantling and treatment of nuclear waste. “Short-lived waste”, which has a half-life of less than 31 years, includes waste from the operation or decommissioning of a power plant: protective clothing, tools, used parts, contaminated rubble, etc. “Long-lived waste” includes residues from the processing of nuclear fuels. It represents only 10 % of the waste, but can remain radioactive for up to 100 000 years or more. The problem is that, as far as we know, we cannot completely neutralise the harmful effects of this waste because we do not know how to annihilate the radioactivity. After World War II, the first “solution” was to dispose of them at sea in concrete or in drums. However, this practice was banned in 1993.

“Securing” radioactive waste

Today, the general idea is to “secure” waste so that its radioactivity disappears naturally over time. Short-lived low- and intermediate-level waste (300 years of maximum hazard) is stored above ground in ultra-secure warehouses (in the United States, Europe - the United Kingdom, France, Sweden, Finland, Spain, Belgium - and Japan). It is first “treated” to prevent its radioactivity from escaping as much as possible. “The process generally involves vitrification, which means heating and melting waste into glass blocks, or cementing them in place, i.e. imprisoning it in this material to prevent any pollution from leaching”, adds Dominique Richit. It is then stored in steel or concrete containers. The most problematic waste, the “high-level waste” (HLW), which is less abundant but more hazardous (sometimes for several hundred thousand years), is currently treated in a similar way and temporarily stored in ultra-secured sites in 14 countries (led by the United States, which has around 100 nuclear reactors, and France, with around 60). 

Sites reaching saturation point

But in the next few years, these sites will be full, mainly because of the upcoming dismantling of nuclear facilities. For example, the pools at the La Hague centre where nuclear waste is temporarily stored could reach saturation as early as 2030. In Finland, the total saturation level is estimated to be 93 %, and 80% in Sweden. The nuclear industry is therefore working on new solutions. For the time being, the preferred option is to bury the waste several hundred metres underground in a suitable geological formation (which will not move for several million years). The most advanced project, “Onkalo”, in Finland, plans to bury the most radioactive waste permanently under more than 400 metres of rock. Other countries such as Canada, Germany, Japan and the United States are considering a similar solution.