Good reasons not to waste nuclear ‘waste’

For decades we have all been told that nuclear waste is an unsolved ‘problem’ which makes future nuclear power development unethical because it will add to a toxic legacy left to poison our descendants thousands of generations into the future. The Yucca mountain controversy in the US and other debates about geological disposal seemingly illustrate the technical impossibility of guaranteeing to isolate a radioactive waste stockpile from the biosphere up to a million years into the future. But there is an easy way to solve this problem, and it doesn’t involve digging deeper holes – politically or physically. It involves remembering the principal ‘R’ word of the environmental movement: recycling.

In actual fact, the worst thing possible we could do with nuclear waste would be to throw it away. Worldwide stockpiles of ‘waste’ from thermal light-water reactors (which comprise the vast majority of civil nuclear reactors) already include enough fissile (or fertile) elements – plutonium, other actinides like americium and neptunium, and uranium (both U-235 and U-238) – to run the world on clean energy for centuries without having to go out and mine another gram of uranium ore anywhere. That so few people appreciate this fact suggests that igorance about all things nuclear is more profound than many of us would like to think, and especially so within the environmental movement.

The UK government, for example, recently carried out a consultation on what should be done with Britain’s plutonium stockpile, which currently totals more than 100 tonnes. The mooted options include continued surface storage, ‘spiking’ it to make it useless to terrorists or other bomb-builders before deep disposal, or recycling it with uranium into ‘mixed oxide’ fuel to be burned in conventional reactors. None of these options make much sense. Instead, the most sensible – and sustainable – option by far is the one ruled out early on in the consultation document, which is to put the plutonium, together with fissile elements from existing waste stockpiles, into a new generation of ‘fast’ reactors and use them to generate zero-carbon electricity.

Few people realise just how inefficient and wasteful the current generation of nuclear reactors actually are, and why they generate relatively large volumes of long-lived waste. This is because only a tiny amount (less than one percent) of the energy in the uranium is burned up in the reactor to generate heat and electricity – the rest is wasted (or worse than wasted, as it then adds to an expensive legacy which is difficult to handle and dispose of). Yet as Tom Blees recounts in his book Prescription for the Planet (especially Chapter 4, which is available free here), fast reactors can utilise 95% or more of the fissile energy in their fuel. Blees proposes a design called the ‘Integral Fast Reactor’ (IFR), originally developed at the Argonne National Laboratory in the United States, and very successful until the programme was cancelled in 1994 by President Clinton to appease anti-nuclear campaigners.

Waste-wise, IFRs or other fast reactors can generate prodigious amounts of clean energy by vastly reducing the current waste stockpile, but they cannot eliminate it altogether. Some fission products remain at the end of the process, and will need to be disposed of in a geological repository – probably after having been stabilised by vitrification (turned into glass). However, it is a misnomer to assume that these need to be isolated from the biosphere for thousands or even millions of years – in fact, after only a few hundred years, the radioactivity levels in the leftover waste will have declined back to those of the original naturally-occurring uranium ore, and they will become functionally safe much sooner. This is not a significant environmental problem, and indeed is much less of a challenge than the waste produced by other industries like electronics or metal smelting, which has no half-life and therefore remains toxic forever.

Fast reactors like the IFR can also be designed with passive safety features. All nuclear accidents so far – from Three Mile Island to Chernobyl to Fukushima – have involved loss of coolant crises, where solid fuel melts down (in the cases of TMI and Japan) or overheats and explodes in the case of Chernobyl. This cannot happen in the IFR design as the coolant would be molten sodium circulating at atmospheric pressure rather than water at very high pressure, and therefore steam explosions due to overheating or containment failures are not a problem. Moreover, fast reactors behave differently from light-water reactors – the hotter they get, the less efficient the fission reaction becomes, and if the overheating continues fission is effectively shut down. (Note that Fukushima was already shut down when its loss of coolant happened – at issue was the heat produced by residual reactive decay in the fuel assemblies.)

So why, if they are so great, are we not using fast reactors already? Partly this is for political reasons, because it has long been thought that ‘breeding’ plutonium adds to proliferation concerns. Actually this is largely a misunderstanding, for all reactors produce plutonium – the issue is the need to design the fuel cycle so that bomb-grade materials are never separated, but fed back into fast reactors whilst still highly radioactive and unusable to terrorists or militaries alike. Fast reactors allow us to destroy plutonium stockpiles, and thereby reduce the dangers of proliferation. The big reason why fast reactors have stayed at the experimental stage (although 500 reactor-years of experience have now been clocked up in different prototypes around the world) is that uranium fuel is simply too cheap to be worth the additional cost of using efficiently or recyling. Only governments can solve this problem, by insisting that recycling be made an integral part of new fourth-generation reactor designs (like the IFR) in order to avoid the need for environmentally-damaging and carbon-intensive uranium mining and processing.

As I mentioned earlier, closing the fuel cycle means that we can look forward to hundreds of years of clean nuclear power without the need to mine anymore uranium. This puts paid to the ‘peak uranium’ argument which is a new favourite for anti-nuclear campaigners – we are certainly not about to run out of fissile elements any time soon. Nor do we need to move straight to thorium, which seems to have become the nuclear fuel of choice for a new crowd of determined enthusiasts (Friends of the Earth supports thorium research, but still opposes uranium, in a bizarre sort of elemental political correctness) largely because it is more abundant naturally than uranium. Thorium would still need some new mining and extraction.

To my mind, the way forward is simple: we need to utilise existing fissile materials in waste stockpiles, together with weapons-grade decommissioned uranium and plutonium, added to ‘depleted uranium’ (U-238) in a new generation of IFR-type reactors. The chance of getting anything built in the near term in the UK or the US is tiny, however – but China has just started up a small-scale fast reactor near Beijing, and Russia may be the first country to build an IFR. Unfortunately, the legacy of decades of anti-nuclear activism in the West means that we will likely fall behind in this new clean-energy race too.

As Tom Blees puts it in his book:

Thus we have a prodigious supply of free fuel that is actually even better than free, for it is material that we are quite desperate to get rid of. Uranium, plutonium, and other actinides, both weapons-grade and otherwise, will go into the IFR plants. Only non-actinides with short half-lives will ever come out. We will eliminate the problems of both radioactive longevity and the potential for nuclear proliferation.

I cannot imagine a more environmentally responsible proposal for tackling both climate change and nuclear waste/proliferation at the same time. Can you?

© Mark Lynas
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