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How 'Green' is Nuclear Power?

I started considering this issue last year, prompted by reports of Green Party members and others who were suggesting that nuclear power was the only way to decarbonise our electricity system, and to reach zero carbon targets.

It is not.

Nuclear generation is not ‘zero carbon’ and over its lifecycle generates more CO2 than renewables, for the same amount of electricity generated.

New nuclear power stations cannot be built in time to make a difference to tackling climate change.

The money would be better invested in cheaper renewables, energy efficiency measures and in developing solutions to store and distribute electricity better.

The evidence for these claims

I started off last year asking myself a simple question: how much CO2 is actually emitted by nuclear compared to alternative electricity generation, such as renewables, fossil fuels etc.

Finding the answer turned out to be anything but simple. It depended on whether you looked at nuclear industry-funded research or independent research. I encountered a lot of obfuscation in terminology and lack of transparency in the assumptions underpinning the research. I found a wide range of figures and conclusions, depending on what perspective you were researching from and who was funding the research. It reminded me of pharmaceutical industry research, where ‘sponsorship bias’ is well-documented. [1]

It also depended on what you counted in the ‘carbon budget’ for constructing and operating different methods of generating electricity. There were studies of nuclear that only looked at the generating phase of the power station, and which did not consider all the other parts of the ‘whole lifecycle’ of energy generation.

In order to generate electricity by nuclear power, the following stages are required, all of which consume energy and generate CO2 emissions in their own right:

· Uranium mining

· Milling

· Conversion

· Enrichment

· Fuel fabrication

· Reactor construction

· Reactor generation

· Spent fuel processing

· Fuel conditioning

· Interim storage

· Permanent geological storage

It is true that the reactor generation phase emits little CO2 (apart from the daily workforce travel) than other parts of the nuclear lifecycle, but some studies have conveniently forgotten some of these energy intensive/CO2 emitting stages. Their calculations therefore have underestimated the contribution nuclear power is making to society’s CO2 emissions. Unlike other forms of generation such as wind, hydro and solar, nuclear reactors require fuel that results in further CO2 emissions after its construction.

Let’s look at a couple of these stages: uranium mining and construction.

Uranium mining

Many people do not know that uranium, the fuel for nuclear reactors, is mined out of the ground, in vast open-cast and underground mines. 42% of the worldwide stock of uranium used in nuclear reactors is imported from Russia and Russian-controlled Kazakhstan. [2] Imports are obviously an issue going forward if the war in Ukraine continues.

There is also a law of diminishing returns – the level of uranium in mined ore is decreasing, and as that happens, more electricity is required to process the power into useable fuel. In a number of mines, ore is processed using electricity from coal-fired power stations. The source of electricity used in the various steps in processing can determine how much CO2 is emitted, and this is responsible for some of the variations in estimates. To my mind, it makes no ecological sense to use fossil fuels to produce nuclear fuel and then transport it half way round the world in order to generate electricity.

Construction of nuclear power stations

Estimates vary according to the design and type of nuclear reactor, but on average, construction of one reactor takes 170,000 to 190,000 tons of concrete, 32,000 to 40,000 tons of steel, over 1,300 tons of copper and over 205,000 tons of other materials. Some of these other materials are very carbon intense (e.g. 1 ton of lithium is the carbon equivalent of 44,000 tons of CO2). [3]

But concrete has a colossal carbon footprint — at least 8% of global emissions caused by humans come from the cement industry alone. [4] Concrete is made by adding sand and gravel to cement, whisking the mixture with water and pouring it into moulds before it dries. Making the cement is the most carbon-intensive part: it involves using fossil fuels to heat a mixture of limestone and clay to more than 1,400 °C in a kiln. When limestone is heated with clays, roughly 600 kilograms of carbon dioxide is released for every tonne of cement produced. A recent estimate for the construction of the Sizewell C nuclear reactor suggested that it would take 6 years of operation of the reactor just to ‘pay back’ the CO2 emitted by using concrete in its the construction. [5]

Lifecycle CO2 emissions from nuclear compared to other forms of electricity generation

In 2008, a meta review of studies of CO2 emissions resulting from different forms of electricity generation was conducted, and found the following: [6]



Median estimate (gCO2e/kwhr) i.e. equivalent CO2 emissions per kilowatt hour


2.5MW, offshore



3.1MW, reservoir



1.5MW, onshore


Solar thermal

80MW, parabolic trough (i.e. large scale solar farm)



Waste wood steam turbine



Mean of various types of reactor

66 (range 1.36 to 288)

Natural gas

Various combined cycle turbines



Various types with scrubbing


This was the only independent comparison between renewables and nuclear I could find. Updated research in 2021 found a broadly similar range of emissions for nuclear power, although a smaller median figure. [7] Another recent study suggested means of 17-27 gCO2e/kwhr for nuclear. [8] All these results are higher than the generally used figures for nuclear power. The UK Government and EDF have used a significantly lower mean figure in modelling the impact of nuclear at 6gCO2e/kwhr, making nuclear appear carbon neutral. [9]

The emissions associated with renewables are essentially completed once the plant is online, whereas a nuclear plant will effectively be emitting into the future, as its fuel is decommissioned and stored. No one knows what the CO2 emissions for the storage phase of radioactive nuclear waste will be. Many options involve lots of concrete, so it is likely that lifecycle CO2 emissions will be pushed up even further.

Using the figures in the table above mean that the new nuclear power station proposed for Sizewell C would emit between 62,400tonnes CO2 and 1,040,000tonnes of CO2 over its lifetime.

This is not a recipe for a zero carbon energy policy.

Will nuclear be in time to make an impact on climate change?

Of the 6 power stations currently still operating in the UK, Hinkley Point B is just about to close this summer, but has been operating at 70% efficiency for a number of years due to cracking. It will have been generating for 46 years. Torness’s closure date has been brought forward to 2028 because of cracking, so if it makes it, it will have operated for 40 years, as will Heysham 2, due to close at the same time. Hartlepool will have lasted for 35 years only. Dungeness B has been out of action since 2018, and in 2021, its immediate de-fuelling was announced, meaning it too operated for just 35 years.

Almost all the UK’s existing nuclear capacity therefore will have been shut down well before the UK Government’s 2050 zero carbon deadline. Only Sizewell B is predicted to continue generating beyond the end of this current decade. It will provide just 3% of the UK’s electricity.

EDF and the UK Government however would point to the new design of the ‘next generation’ of nuclear power stations: the European Pressurised Reactor (EPR). EDF claims its EPR will last 60 years, and the UK Government uses this figure in its modelling. [10] The longer nuclear reactors can generate electricity, the lower the assumed CO2 emissions over the lifecycle.

What’s the EPR track record – is it any better than the existing UK nuclear power stations?

Construction of the Okiluoto 3 EPR in Finland was started in 2005 and was estimated to start generating in 2010. It actually began generation in March 2022. Flamanville 3 in France began construction in 2007 and is still not operational, having suffered a number of issues with weak steel used in its construction. The current estimate is for fuelling up to start next year. 2 Chinese EPRs at Taishan were the first to start generating electricity. Taishan 1 was taken off line last December due to faulty fuel rod cladding. There is speculation that this was due to a design flaw, suggesting potential operational issues for all EPR’s in future. [11]

The EPR at Hinckley Point C is the only new nuclear power station under construction in the UK. It was one of 8 announced in 2010 (yes, the Government already announced 8 would be built 12 years ago, and we’re still waiting). Initially, it was planned that generation would start in 2023. That has now been extended for 3 years. In March 2022, EDF announced that it expected further delays and costs due to the war in Ukraine. Every construction delay adds to the carbon cost of construction.

The UK Government is therefore relying on the EPR design which has shown itself to take between 3 -5 times longer to build and may go 3–5 times over budget.

This must throw the Government’s CO2 savings projections into considerable doubt. The Sizewell C analysis in fact suggests that by the time it is built, the power station will actually be a net contributor to CO2 emissions, and so will not be carbon neutral. [12]

This is because other technologies, notably renewables, will decarbonise the electricity supply system much more quickly than new nuclear can be built, and so renewables will already have saved the carbon we need nuclear to save. By 2050, 90% of the world’s electricity will be generated by renewables. [13] Analysts now expect that the UK electricity grid will be carbon neutral by the mid-2030’s without the use of new nuclear. [14]

Better use of the investment

It is still the case that investing in energy efficiency, developing more renewable generation and improving the storage and distribution of electricity will do more in a much shorter time to meet our climate change targets and keep energy costs down, than nuclear ever could.

Since 2009, the cost estimates for solar have dropped by 90% and wind by 70%, but those for nuclear actually increased by 33%. [15]

Building 8 new nuclear power stations will cost at least £162,500 Billion [16] Estimated costs for the long term disposal of spent fuel is around £131 Billion. [17]

Just imagine how many homes can be made energy efficient, how many community-scale renewable energy projects can be developed and how many gas and oil boilers can be replaced for this money. And in the process, how many hard-pressed families can be supported to heat their homes and cope with rapidly rising energy bills.


Nuclear power actually creates more CO2 than renewables for the same amount of electricity generated, when all the phases of the nuclear lifecycle are taken into account.

New nuclear power stations cannot be built in time to make a difference to climate change. An energy strategy for the UK based on nuclear generation can only add to CO2 emissions.

Politicians such as Murdo Fraser of the Scottish Conservatives, who are quoted as opposing the Scottish Government’s ‘no nukes’ policy alleging that nuclear power is ‘without carbon emissions’ are clearly wrong. [18] Those who claim nuclear power is the only way to decarbonise our electricity supply are wrong.

The essence of an effective response to the climate emergency is speed. This means investing in proven technology such as renewable and energy efficiency measures, rather than continuing to invest in a failed nuclear technology.

Nuclear is a technology whose time has passed.

[1] Jefferson 2020, reported in the Journal of the Royal Society of Medicine at [2] [3] B Sovacool, 2008, Valuing the Greenhouse Gas Emissions from Nuclear Power: A Critical Survey Energy Policy 36(8):2940-2953 at [4] Nature 597, 593-594 (2021) at [5] Prof Steve Thomas, 2021 Sizewell C carbon savings at [6] B Sovacool op cit [7] E Warner & G Heath, Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation Journal of Industrial Ecology, 16, S73, (2012) quoted in Thomas 2021 op cit [8] Pomponi and Hart 2021, The greenhouse gas emissions of nuclear energy – Life cycle assessment of a European pressurised reactor’, Applied Energy 290 116743 at [9] UK Climate Change Committee [10] wp-content/ipc/uploads/projects/EN010001/EN010001-005331-8.14%20Sustainability%20Statement%201.pdf Page 83 [11] The Diplomat 2021 at [12] Thomas op cit [13] [14] Thomas op cit [15] [16] The 2016 estimate for Hinkley Point C, the only nuclear reactor under construction in the UK was that it would cost £20.3billion (EDF figure) [17] UK Nuclear Decommissioning Authority [18] Reported in The Scotsman, January 2022 at

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