Last month Cumbria Trust reported that the Swedish Environmental Court had blocked a licence application to construct a Geological Disposal Facility (GDF) for spent nuclear fuel after serious concerns were raised over the corrosion of the copper canisters used in the KBS-3 method. The same containment method is intended to be used in the UK. This court ruling was a success for MKG, the Swedish environmental organisation which receives government funding to act as a critical friend, scrutinising Sweden’s plan to bury nuclear waste.
MKG have now released some further details which show that the corrosion concerns are shared by experts within the Swedish regulator, SSM. While the nuclear industry, including the UK’s Radioactive Waste Management (RWM) seem keen to minimise the significance of this court ruling, by describing it as a delay and a request for more information, it appears the problem may be more fundamental, and could lead to this method of KBS-3 copper encapsulation being abandoned. This would damage the UK’s search process.
A key assumption with the KBS-3 method is that copper does not corrode in anoxic conditions, that is without the presence of oxygen. While there will be oxygen present at first, once the canisters are placed within the bentonite clay, bacteria and chemical processes consume the oxygen, creating the desired anoxic environment. However, it is becoming increasingly clear that even without oxygen, the copper begins to corrode by pitting. The heat generated by the spent fuel appears to be a significant factor in accelerating this pitting process. These capsules were intended to remain intact for a million years, but tests have suggested that they may well fail much sooner.
The significance of the problem goes well beyond this encapsulation method. There are lessons that should be learned, but the question is whether the nuclear industry will be open enough to do so. One key lesson is that funding a critical friend NGO such as MKG, can help to identify problems and reduce the impact of groupthink which leads to irrational decision-making. Another appears to be that we are prone to over-confidence in engineering. Isolating nuclear waste from the surface for a million years, particularly waste types which produce a great deal of heat, is complex. While we can test potential containment methods for around a generation, we need to be confident that these methods will continue to work for 30,000 generations.
“There is only one form of containment for liquids and gases which has been demonstrated to work for millions of years, even under great pressure, and that is geological formations. We have a vast quantity of evidence from the oil and gas industry of rock formations which have isolated hydrocarbons from the surface for many millions of years. So while Cumbria Trust continues to support the principle of geological disposal, as potentially the least bad solution to an existing problem, the key to its success must be the geology in which it is constructed.”
Any search process for a GDF site must begin with suitable geology and the failed attempts in Cumbria have concluded that the search should move to an area of simple geology and low groundwater flow. Cumbria Trust fears that the selective blindness which has led to the previous failures of the search process, will result in another attempt to target Cumbria despite its complex geology.