Geological Repositories and How Deep Does That Rabbit Hole Go?

The option that a quick perusal of most academic literature and government proposals as the safest or 'best' option for dealing with nuclear waste is the creation of geological repositories (GRs). Essentially after exploring various ways of dealing with nuclear waste, we're going to return to the time-old tradition of burying things to keep them a) safe and b) out of sight.

The science behind GRs is fairly simple: the radioactive waste put deep enough and behind enough stone, clay and other geological materials, could potentially be contained safely for up to millions of years (Wiley and Sons 1995). GRs are touted as the cheap (relatively), low maintenance solution to our nuclear waste disposal needs. At a conference I attended on nuclear waste over summer, global experts on nuclear waste disposal from around the world unanimously agreed on geological disposal as the most viable and desirable method of containing our waste. Using the natural shield of geological material in these areas was a cheap (relatively) and efficient way of containing waste. The commonly explored and implemented concept of a GR is for the waste to be stored in solid form within canisters that are placed deep underground and after this, the tunnel will be backfilled in with impermeable materials

GRs will have both a surface and underground facility (pictured below in a conceptual image from the British Radioactive Waste Management group); the above ground will be much smaller, and most likely just be composed of several management facilities, below ground however could stretch for up to 10-20 square kilometres. Most plans for GRs place them at depths between 300m and 1000m. For perspective, the London Underground's deepest station is around 60m deep, and the deepest hole ever dug by humans is 12,000m deep.

However not every location can be a GR. The conditions for a GR must be the best available for managing radioactive wastes. The factors most often considered are:

1. The tectonic stability of the region, how often do they have large seismic events?
2. The composition and flow of groundwater in the region, is the water highly reactive with either the radioactive nuclides or the canisters in which the nuclear waste will be contained with. Once contaminated with radioactive particles, what are the likelihoods of these particles entering the biosphere?
3. The composition of the bedrock, how fractured or porous is it, how will this affect the aforementioned groundwater flow

I was lucky enough to visit the south of Sweden last summer to observe the process by which the government was exploring the viability of and science behind geological repositories. This was going on in two locations, the neighbouring municipalities of Oskarshamn and Forsmark.

Me at the Aspö Laboratory!

From 1977-2001 the Swedes undertook feasibility studies throughout the country narrowing down in stages the number of feasible sites. Geological overviews at these sites were all promising with low levels of fracturing and seismic activity, alongside relatively 'dry' (low groundwater flow) bedrock (Westerberg 2010). To further study the feasibility of the two sites a underground laboratory was established in Oskarshamn, known as the Aspö Hard Rock Laboratory. Created in 1986, this unique 'laboratory' is composed of a series of tunnels up to 450m deep exploring a 'realistic and undisturbed rock environment' (SKB, 2013) at the depth that the government plans to store waste at (Byegård 1998). It gave them vital insights into all of the factors I mentioned above plus one more valuable aspect: what does drilling large tunnels deep underground do to the surrounding rock? My visit to the region included a trip down into the laboratory which I found fascinating from a geological perspective, but not something I would recommend anyone claustrophobic. Their research proved vital and in 2014 it was decided that the plans for the creation of a geological repository in Forsmark would begin.

It took Sweden around 30 years, but they have established a very solid base and plan for the creation of a geological repository, however this journey was not without its objections, objections levered at nuclear projects globally. 'NIMBY' or 'not in my back yard', the term used to describe people who object to the siting of something perceived as unpleasant or hazardous in their own neighbourhood. This issue very nearly shut down the Swedish program, and it played a big part in Obama's decision to put a stop to the creation of a GR at Yucca mountain (although this was recently reopened by Big Man Trump). So how did the Swedes pull through where the Americans faltered? Well I'll be discussing that next week!