The Atomic Age

Claims that nuclear power is a ‘low carbon’ energy source fall apart under scrutiny, writes Keith Barnham. Far from coming in at six grams of CO2 per unit of electricity for Hinkley C, as the Climate Change Committee believes, the true figure is probably well above 50 grams – breaching the CCC’s recommended limit for new sources of power generation beyond 2030.

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But what is the carbon footprint of nuclear power? I have trawled the literature and found that there is no scientific consensus on the lifetime carbon emissions of nuclear electricity.

Remarkably, half of the most rigorous published analyses have a carbon footprint for nuclear power above the limit recommended by the UK government’s official climate change advisor, the Committee on Climate Change (CCC).

According to the CCC, if we are to avoid the worst effects of climate change, by 2030 all electricity should be generated with less than 50 grams of carbon dioxide emitted for each kilowatt-hour (50 gCO₂/kWh).

Since all new generators have lifetimes well over 20 years, I believe this limit should be imposed on all new electricity supply systems here and now – and all the more so for those with lifetimes spanning many decades.

Note that thanks to long construction times for the EPR design and a forthcoming legal challenge, it’s entirely possible that the planned Hinkley C reactor will not be completed until 2030 or beyond. It will then be subsidised for the first 35 years of its projected 60 year lifetime – taking us through until 2090.

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What’s the carbon footprint of nuclear power?

There have been nearly three hundred papers on the carbon footprint of nuclear power in scientific journals and reports in recent years. Two peer-reviewed papers have critically assessed the literature in the way Nugent and Sovacool compared renewable LCAs.

The first was by Benjamin Sovacool himself [1]. He reviewed 103 published LCA studies and filtered them down to 19, which had an acceptably rigorous scientific approach. The carbon footprints ranged from 3 to 200 gCO₂/kWh. The average carbon footprint was 66 gCO₂/kWh, which is above the CCC limit.

In 2012, four years after Sovacool’s paper, Ethan Warner and Garvin Heath found 274 papers containing nuclear LCAs [2]. They filtered them down to 27 for further consideration. These yielded 99 estimates of carbon footprints which the authors describe as “independent”.

Their data for carbon emissions ranged from 4 to 220 gCO₂/kWh. They did not report an average but rather a median value: half the estimates were below 13 gCO₂/kWh.

These two reviews of the published literature, often called meta-analyses, produced conflicting results. One suggests the carbon footprint is above the CCC limit, the other well below.

Looking in more detail at the Warner and Heath meta-review it becomes clear that their 99 estimates are not all ‘independent’ – in the sense of independent from each other – as they come from only 27 papers.

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Using 0.005% ore, nuclear has higher carbon emissions than gas

Nuclear fuel preparation begins with the mining of uranium containing ores, followed by the crushing of the ore then extraction of the uranium from the powdered ore chemically. All three stages take a lot of energy, most of which comes from fossil fuels. The inescapable fact is that the lower the concentration of uranium in the ore, the higher the fossil fuel energy required to extract uranium.

Table 12 in the Berteen paper confirms the van Leeuwen result that for ore with uranium concentration around 0.01% the carbon footprint of nuclear electricity could be as high as that of electricity generation from natural gas.

This remarkable observation has been further confirmed in a report from the Austrian Institute of Ecology by Andrea Wallner and co-workers. They also point out that using ore with uranium concentration around 0.01% could result in more energy being input to prepare the fuel, build the reactor and so on, than will be generated by the reactor in its lifetime.

According to figures van Leeuwen has compiled from the WISE Uranium Project around 37% of the identified uranium reserves have an ore grade below 0.05%.

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Conclusions

There is no consensus in the scientific literature as to the carbon footprint of existing nuclear reactors. I have more confidence in the six highest LCAs because two of them have been independently re-assessed and – in contrast to the two lowest LCAs – the higher analyses have taken realistic account of the uncertainties in the three most problematic parts of the nuclear life cycle.

As all six are either above, or have error bars that reach above, the CCC’s 2030 threshold of 50 gCO₂/kWh, the balance of the evidence of the six most robust LCAs is that the carbon footprint of nuclear power is above the CCC’s recommended limit.

And of course these figures apply to existing nuclear power stations, not the EPR design planned for Hinkley C. As we have seen, the EPR’s very high cost suggests considerably higher emissions in the construction stage. So too does the fact that, over its projected 60-year lifetime, it will be using uranium from very low quality ores.

The likely delay due to the Austrian appeal against the European Commission’s decision on the EPR subsidy offers an opportunity for a full, independent and peer reviewed assessment of the environmental impact of this complex and expensive new technology.

Read more at False solution: Nuclear power is not ‘low carbon’