The Problem of Nuclear Waste Disposal - and How Finland Solved It
"Even if all nuclear power plants were shut down today, there's a mountain of radioactive waste waiting to be disposed of," reports Ars Technica. "Yet only Finland has an approved solution for nuclear waste disposal, while projects in the US, UK, and Germany have failed for decades, and progress is also slow in other countries." So how did Finland construct a safe nuclear waste repository? Ars Technica asked Antti Mustonen, who's a research manager with Posiva, the organization in charge of the Finnish repository:Finland has a lot of hard crystalline bedrock and many places that are potentially suitable for a repository. The country eventually chose an island on the Baltic coast for its Onkalo repository, and it hopes to seal off the first tunnel of nuclear waste sometime around 2025.... Even after it has cooled in ponds for decades, spent nuclear fuel gives out heat by radioactive decay, raising the temperature near the waste canisters. This heat could potentially corrode the canisters, compromise the bentonite, or even crack the rock face. Therefore, the Finnish and Swedish designs separate individual waste canisters in their own disposal shafts to avoid excessive heat buildup.... Posiva is currently conducting a long-term, full-sized demonstration using heaters in dummy canisters surrounded by bentonite and temperature probes. After three years, the temperature at the canister boundary is about 70 C, Mustonen said. A similar test in Switzerland lasted 18 years and found that bentonite "remains suitable as a sealing material" up to at least 100 degrees C.... But to project how the rock and groundwater will affect humans living near the site in future millennia, the scientists must model that numerically using the tests and data as the starting point. "We have modeled to that million years... with different scenarios and what the likely releases [are], and it seems that the releases are acceptable," Mustonen told me.... Scientists then project what will happen to the waste over the next million years, assuming everything works as planned. They also model for several "what if" scenarios. This projection includes looking at the stresses and groundwater pressures caused by possibilities like being buried deep under a future ice sheet and then having that ice sheet melt away, sea level changes, changes in groundwater chemistry, and failures of canisters. At Onkalo, even in the worst case, scientists calculate that the maximum dose released to humans would be one-tenth of the regulatory limit, which itself is about a hundredth of the normal dose that Finns receive every year. But the article also asks what Finland's experience can teach other countries. One person who worked on America's unsuccessful Yucca Mountain project was Dr. Jane Long, former associate director for energy and environment at Lawrence Livermore National Laboratory. Long tells the site that "They should have set requirements for an inherently safe site and then investigated whether the site met the requirements instead of choosing the site for political reasons and then trying to show the site was suitable." And they seem to agree in Finland:"More than the geology, I think it's socio-economic aspects" that determine if a project can go ahead, Mustonen told me. A key lesson is that the top-down designation of sites for nuclear waste disposal has generally failed. The UK failed in 1987, 1997, and 2013. In the US, politicians campaigned against the Yucca Mountain project, characterizing its authorization as the "Screw Nevada Bill...." Yucca Mountain's wasted $15 billion pales in comparison to the roughly $50 billion in damages that American taxpayers have had to pay to nuclear utilities because the government was unable to honor its commitment to receive nuclear waste by 1998. Meanwhile, more waste is piling up. Thanks to Slashdot reader atcclears for submitting the story.
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