This is the fourth in the series of six articles on nuclear being publishing the journal of the South Australian Chamber of Mines and Energy. Our topic this time was radioactive waste in the context of a potential future Australian nuclear power industry. This article is co-authored with Barry Brook.
As before, please be mindful that word limits for print publications are always tough when you are tackling topics that require a bit of context, understanding and comparison, so if you are concerned that anything received brief treatment, the comment thread is yours.
In the big hitting concerns about nuclear power, long-lived radioactive waste may just be the most powerful in the public eye. But the fear-laden awareness of long-lived radioactive waste belies many of the realities of its management.
The best start for responsible management of any hazardous waste is to capture and contain it at the source. Nuclear power does this. Fossil fuels do not. The combustion of coal and other fossil fuels produces toxic fly ash, mercury, radioisotopes, nitrates and sulphates, and of course, huge amounts of carbon dioxide – globally, almost 30 billion tonnes each year. Fossil fuel is both a huge short-term health problem and the recipe for a long-term climate breakdown. Already, nuclear is way out in front.
Secondly, radioactive waste is perceived as complex. This is far from the truth. Radioactive material is one of the most predictable, easily monitored and best understood forms of waste. We know what it does, and how it does it, forever, and we manage it accordingly. Imagine a very loud noise source that you cannot turn off, that is very, very slowly getting quieter. Stand too close for too long and you will get an injury or even go deaf. How would you manage such a thing? Contain it in dense material, put distance between it and you, and let it quieten down. That is what happens for radioactive material in long-term storage, and it is very secure. The material in Dry Cask Storage at Fukushima bore the full brunt of the tsunamis, with no damage. The image of the leaky, rusty barrel being stuffed into a tree by Mr Burns is, quite appropriately, a joke.
Thirdly, the quantities in question are relatively very small. Australia produces (and somehow manages) around 1.1 million tons of hazardous waste every single year. A large-scale 25 GW nuclear power industry would add a mere 750 tons, taking up just 250 m3 (six-and-a-half standard shipping containers). But of course that doesn’t do it justice. This small quantity of contained waste would be displacing vast quantities of uncontained pollutants from fossil fuels; toxins and other unwanted by products that we have simply come to accept as the cost of reliable energy. The quantities for nuclear fission are so manageable that new reactor designs include a facility to hold all of the waste for the 60 year life of the plant, right there on site.
Still, a problem remains. We must babysit the radioactive waste for tens or hundreds of millennia. For instance, plutonium produced in nuclear reactors has a half-life of 24,100 years, meaning you have to wait a few hundred thousand years for it to lose most of its radioactivity. Although storage in deep, geologically stable repositories is technically possible, the idea of bequeathing future generations this responsibility leaves many people understandably uncomfortable.
There is, however, a much better option: consume the long-lived waste, and in so doing, generate huge amounts of zero-carbon electricity. This can be done in Fast Reactors.
Plutonium and other ‘transuranics’ (elements heavier than uranium, such as neptunium, curium and americium – also called ‘actinides’) – are the substances responsible for the long-lived radioactivity of nuclear waste. It makes up about 2% of the spent fuel from current light water reactors. About 93% is uranium. The uranium is almost entirely the more plentiful, heavier and less-radioactive isotope U-238 which, unlike the rarer U-235, is mostly left unused in today’s commercial reactors. The Fast Reactors are able to consume it all, as well as all the plutonium and other transuranics, converting them into energy. That increases the energy density of uranium about 150 times.
What’s left behind after multiple recycles are the ‘fission products’, about 5 % of the original (once-through) waste, which are the lighter elements created when the actinides are split apart. This is the ‘real’ nuclear waste.
The fission products need to be managed for about 300 years, after which time they’ve lost 99.9% of their original potency. To safely take them to this point, the fission products can be ‘vitrified’ (entombed within a highly durable glass-like matrix), or encapsulated within the Australian-designed ‘synroc’. This highlights another huge plus for the future of nuclear power. Not only can all of the world’s stockpile of spent nuclear fuel be consumed in Fast Reactors to produce copious amounts of zero-carbon energy, but what remains is a comparative cinch to take care of.
So nuclear waste stops being a major headache, and turns into an asset. An incredibly valuable asset, as it turns out. In the US alone, there is 10 times more energy in already-mined depleted uranium (about 700,000 tonnes) and spent nuclear fuel, just sitting there in stockpiles, than there is coal in the ground. This is a multi-trillion dollar, zero-carbon energy resource, waiting to be harnessed.
To recap then: waste from nuclear reactors is tiny in volume and fully contained at the source. It is well understood, and its safe management is relatively straightforward. By producing it, we would displace the vast uncontained toxic pollution from our fossil-fuel driven energy production, and take our most decisive step to resolving climate change. Within decades, it will be reused to produce yet more vast quantities of zero-carbon energy, leaving a tiny fraction of much shorter-lived waste behind. On the road to sustainability, this would be a great leap forward for Australia.