The Waste We Already Accept

Part 1: Nuclear waste in SA

Stewardship of international used nuclear fuel in South Australia is a rare opportunity. The analysis and decisions must include all stakeholders and be informed by the most accurate experience and knowledge.

If it doesn’t make sense to proceed – like we conservatively found with conventional nuclear energy in South Australia under our current weak power capacity and climate policies – then let’s not. But let’s also not give equal weight to fear, misinformation or rejection dressed up as “concerns”. A rhetorical question about speculative safety in ten thousand years time is no substitute for finding things out if one truly feels compelled to have an opinion.

cherenkovIn this vein, let’s look at what’s worth all this money. Used fuel out of light water reactors looks just like fresh fuel, it’s just extremely radioactive. It’s so “hot” that over ten metres of water is used to ensure plenty of shielding, which results in intensely bright Cherenkov radiation. However, it is no longer being irradiated and is already losing its overall radioactivity.

It is secured under water on-site for a few years, and then (at an increasing number of sites) is transferred into dry casks. A cask constructed of several inch-thick steel may be loaded with up to 15 tons of nuclear fuel, still in the form of sealed assemblies. These sealed and cooled dry casks have different outer casings for loading, transport and storage. In some places like Switzerland’s Zwilag the transport casks are simply lined up in a tidy warehouse. Alternatively, dry casks can be loaded into concrete bunkers, or fitted with concrete overpacks.

overpack

And there they stay: solid byproducts in the most solid shells ever engineered by humans. The initial conservative findings indicate an international demand for a stewardship service of $1.75 million per metric tonne. This adds up extremely quickly. These funds front-load the finances for the sort of secure facility required – an Interim Storage Facility – while the long term permanent solution is carefully planned.

Part 2: Fossil waste in SA

Why is this worth so much? The responsible handling and storage of this material comes with rather strict international standards and containment must be assured. There are significant costs involved. If it can be performed straightforwardly, the state will essentially be profiting from the custody of massive blocks of concrete.

But what if it can’t? What would a leak mean? Raised levels of radiation in a secure facility staffed by highly trained professionals who understand the hazard. Australia has ARPANSA which is solely responsible for regulating this sort of thing. The IAEA will also be involved.

And what is the fundamental basis of the hazard? It is the radiation being emitted by elements like plutonium, and its potential effects upon DNA. But Bernard Cohen, late professor emeritus from the University of Philadelphia plainly described the actual risks decades ago. He demonstrated clearly how the myth of supreme plutonium toxicity is a falsehood, and cited botulinum toxin – the basis of botox – as substantially more lethal.

Let’s put this in perspective. This dry casked material exists because a nuclear reactor somewhere has already provided substantial and constant amounts of electricity instead of a coal or gas plant – which are what South Australia uses. The carbon dioxide expelled by the latter is not sequestered from the environment. What if it was?

What if fossil fueled power plants contained their byproducts the way nuclear energy does?

Carbon dioxide has a density of 1.977 g/m³, but cool and compress it to dry ice and it increases to 1562 g/m³. Given the interior dimensions of those dry casks (11.48 m³) each could contain 17.9 kg of dry ice.

dry_ice_block

In the 2014-2015 financial year a 4,557 gigawatt hour share of South Australian electricity was derived from gas. Assuming a 500 tonne per GWh emissions intensity and that this is all CO₂, it resulted in 2,278,500 tonnes. So, to contain just the emissions from gas from last year would demand over 127 million casks, at a rate of many thousands per hour, non-stop.

Dry cask storage for nuclear fuel is what carbon capture wishes it could be.

So once again, what would a leak mean – not of plutonium, or (heaven forbid) botulinum toxin – but of carbon dioxide? These casks are already over-engineered for containing irradiated fuel assemblies; conceivably they could contain this CO₂ even after it has sublimed from solid to pressurised gas. A slow leak in one cask would simply mean a total waste of money and effort. But a sudden release of pressure would be a deadly hazard for anyone in the vicinity, as suffocating gas expands nearly eight hundred times in volume. It would be like a limnic eruption. It couldn’t be so easily detected in trace amounts, like we can do for radiation, until it was too late. Such an accident is probably rather unlikely, but considering that used nuclear fuel is not stored under this sort of pressure, it looks like the better bet.

But if we’re still averse to nuclear energy, containing the CO₂ is the only way to truly eliminate our emissions. Newer renewable energy sources reach inherent limits and “just building more” is yet to succeed anywhere.

a01e82d1-ec5e-4f75-9b98-e1be690c7435

AEMO’s official high demand projection to 2025.

In reality, annual use of gas in South Australia will increase by around 75% within a decade. The alternative would be to increase imports from interstate – largely coal-fueled generation. Modelling indicates further expansion of wind or solar in SA just doesn’t replace the need for this firm, scheduled capacity.

This expanded reliance on gas, and the fact that we realistically won’t be capturing and storing the emissions in any form, is grim news for South Australia.

The politics concerning global efforts to reduce emissions  are fluid. It would be wise to plan now for a contingency in which external pressure is applied to Australia to more rapidly decarbonise. Action taken now to settle policy for the delivery and operation of nuclear power would enable it to potentially contribute to a reduction in carbon emissions. While it is not clear whether nuclear power would be the best choice for Australia beyond 2030, it is important that it not be precluded as an option.

Can we really afford to wait to be told we’re on the wrong track? I think it’s time for us to make our own future.

 

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2 thoughts on “The Waste We Already Accept

  1. With the start of Gorgon CO2 from unburnt gas should be separated by zeolite sieve and injected into brine aquifiers under Barrow Island, eventually accumulating 120 Mt. If something goes wrong like Lake Nyos or Porter Ranch the WA and federal governments will pay any bills or more likely shrug it off.

    SA’s forseeable depenedence on both interstate coal or LNG competing gas is not only short sighted economics but makes a mockery of emissions pledges. If they can find $50 bn for diesel submarines I suggest diverting a fraction of that for an SA nuke and beefed up iinterstate transmission.

  2. Thank you for this excellent blog. I look forward to every post.
    One nit-pick from a fellow chemist. Dry ice is dense, sinks in water. Correcting units error and uncertainty in density of dry ice gives 18-20 Mt per cask.

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