Nuclear reactors currently have lifetimes of 30-40 years, although the lifetimes of some reactors have apparently been extended to 60 years. Building one more generation of nuclear power stations appears to be the limit using current estimates of ore supply (ie. resources), and will help to provide a solution to fill the energy gap until renewable technologies, smart grids,[B] energy storage and adequate interconnectivity are available on a large-scale.

A thorium nuclear fuel cycle is also possible. This cycle is being tested in India but is no longer being investigated elsewhere. This appears to be a relatively immature technology not yet ready for deployment to mitigate climate change.

Planning and construction

However, the time required to actually build and commission a nuclear power station also needs to be considered. In Europe there are two examples of building the third generation European Pressurised Water Reactor (EPR). The Olkiluoto 3 reactor in Finland should have taken four years to build. It was started in 2005 and commenced operating in 2023.[29] The construction of a second EPR reactor on that site was cancelled in 2015. Similarly, construction of the Flamanville reactor in France was started in December 2007, with a planned five-year construction period, and went into operation in late 2024.

If time for design and planning consent is included, then any decision taken today to build a nuclear power station in the UK is in danger of ending up with a reactor that is running out of fuel before the end of its life.

Fast breeder reactors use uranium sixty times more efficiently than pressurised water reactors (PWRs). They consume some of the waste plutonium and partly burnt uranium fuel from PWRs and produce yet more plutonium-239. The Russian BN-600 fast breeder reactor has operated since 1981 and a new version, the BN-800, has been in operation in Russia since 2014[30].

However, an international review of fast breeder reactors in 2010 concluded After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries and The breeder reactor dream is not dead but it has receded far into the future. [31] Currently, in Europe and the USA such reactors are still at the design stage.[32]

An important factor that needs to be considered in the rational planning of any energy source, including nuclear power, is the energy return on energy invested (EROI). This can be defined as the delivered energy divided by the total energy that has been invested to produce that energy. Thus, an energy source with an EROI less than 1 produces less energy than it consumes. It is probable that a nation s principal power source must have an EROI in excess of 10 to maintain anything approaching the complexity of our present society.[33]

It appears that the EROI of nuclear power depends on numerous factors and is hard to calculate. It has been suggested that it is unlikely to exceed 10 or 11.[34]

For any energy source it is also necessary to consider the energy break even time, which is the time taken to pay back the energy invested in developing a source with the cumulative energy supplied by that source. Energy break even time is important, because, without massive subsidies, investors are unlikely to be interested in financing schemes in which the energy payback time exceeds five years.

According to a detailed life-cycle analysis, pressurised water reactors (PWRs) have an energy payback-time of 6.5 years.[35] As PWRs have a projected lifetime of no more than 40 years the maximum estimated EROI over this period can be estimated as (40)/6.5 = 6.15. However, it can be argued that this estimate is conservative in that it relies on results from an earlier generation of less efficient PWRs and takes no account of potential lifetime extensions.[36]

Against this it has been argued that the EROI for future nuclear power sources does not take into consideration the decline in net energy caused by a switch to progressively lower grades of uranium ore driven by the depletion of the best ores[37]. Further, it could be argued that even if the EROI could be increased to 10, this would not, as we have observed above, be enough for a principal energy source to support our society.[38]

Nuclear power in UK is expensive. At the end of 2023 the price for Hinkley Point C electricity was predicted to be 128.09 per MWh, when it starts producing; but this is likely to rise.[39] Meanwhile, according to DESNZ[40], the prices for projects to be commissioned in 2025 are likely to be:-

       CCGT (gas) 114 per MWh

       Offshore wind 44 per MWh

       Onshore wind 38 per MWh

       Large scale solar 41 per MWh

How will nuclear power contribute to the reduction of UK s greenhouse gas emissions?

Nuclear energy is called clean or low carbon in the sense that the marginal greenhouse gas emissions from generating an additional kilowatt.hour of energy are close to zero.

However, such statements take no account of the emissions generated by building a nuclear power station, mining, processing and transporting ores and enriching the uranium-235 content, manufacturing fuel rods and, eventually, decommissioning the power station and safely disposing of the waste, particularly the high-level waste.

In recent years detailed life-cycle analyses of the production of energy by nuclear power stations have led to a range of estimates from 8 to 64 g CO₂ per kWh.[41] A report for EDF, who operate Torness station, in UK, calculate lifetime emissions of 16.5 g CO₂ per kWh.[42] These figures cover a large range, and demonstrate the difficulty of remotely accurate assessments.

For comparison, a 2014 life cycle analysis of offshore wind arrays came up with emissions of 18 to 31 g CO₂ per kWh[43]; while a more recent one for solar photo voltaic systems calculated emissions as 14 to 73 g CO₂ per kWh[44]. The range of all these figures demonstrates how difficult it is to compare them. But suffice to say that they are definitely significantly lower than those from coal or gas.

So nuclear power may not be the lowest carbon technology available today to help meet the 81% reduction in UK greenhouse gas emissions from 1990 levels by 2035, which was announced by the Prime Minister at COP 29. Although far less than coal or gas-fired power stations, even when such stations are fitted with carbon capture and storage (CCS), their emissions are not insubstantial and appear to be comparable with those from wind and solar photovoltaic.

A new generation of nuclear power stations could then provide a solution in supplying baseload electricity, at least until renewable technologies and the necessary accompanying grid solutions, including energy storage, are sufficiently well established.

What are the risks of nuclear power?

Nuclear power poses risks around accidents, terrorism and waste disposal. These risks are compounded as more nuclear power stations are built in more countries.[45] Here risks are only considered qualitatively because there is so much uncertainty in estimating the risks quantitatively.

First, there is potential for lethal, widespread, extremely costly and long-lasting damage from any nuclear accident. In spite of a relatively safe record over the years, nuclear power stations will always be susceptible to human error and unexpected events, even with modern technology (Three Mile Island 1975, Chernobyl 1986, Thorp 2005 and Fukushima 2011 are examples of accidents). Having said this, designs have been refined over time, and more safety measures are now included. In particular, duplicate emergency cooling systems are now used; and passive emergency cooling systems are emerging, that require no external power to operate[46].

Second, terrorists could acquire material from nuclear programmes to build a nuclear weapon or a dirty bomb (one that contaminates a wide area around the site of a conventional explosion with radioactive material). Either scenario could lead to the death, immediate or delayed, and injury of a very large numbers of people. Terrorists may also directly attack a nuclear facility with unpredictable but probably dire consequences.

The third risk centres on high-level waste (HLW) produced from waste fuel and the decommissioning of power stations. What right do we have to leave this hazard for thousands of future generations? The UK already has about 1,500 m³ of high-level liquid waste at Sellafield[47]. A 1 GW reactor produces about 0.5 m³ (5 tonnes) of solid HLW per year, so the annual increase in volume of HLW from a new generation of reactors is likely to be relatively small.[48] However, in spite of extensive research over at least the last 30 years, no acceptable underground site in the UK has been identified where high level waste can either be safely stored or disposed of. Plutonium-239, found in irradiated fuel, has a half-life of 24,400 years and consequently will remain hazardous for around 250,000 years. It decays into uranium-235 with a half-life of 710,000 years.[49] Although the hazard remains for millions of years, it is generated, in theory, by a relatively small volume (less than a 22 metre cube of high-level and spent fuel waste for the UK so far) yet it has to be broken up into safe, smaller volumes which have to be isolated from the biosphere for many thousands of years.

In summary, it is hard to fully and quantitatively assess the risks posed by nuclear power, particularly in comparison with other sources of energy. Many people, including voters, feel deeply uneasy at the prospect of an expanding nuclear power industry. Fear of radioactivity and distrust of the nuclear industry among the general population are just as likely to play a significant role in any political decision about nuclear power as the arguments presented here.[50]

Are there adequate, alternative, low carbon sources of electricity?

The answer to this question is undoubtedly a qualified yes , depending on how energy demand can be reduced, how energy can be used more efficiently in future, how it can be stored, and on whether renewable sources can be installed fast enough. The UK is investing strongly in renewables. In 2023 renewables, mainly wind, bioenergy and solar, delivered 46.4% of the UK s electricity generation.[51] It must be remembered, though, that electricity production comprises only around 15% of UK s total energy consumption.

Renewable energy means that the energy source is infinite on a human timescale, free and largely derived from the Sun or the Moon s rotation about the Earth. Renewable and well-tested technologies in the form of onshore and offshore wind turbines, hydroelectricity, tidal barrages, and photovoltaic panels already exist. Some have operated for decades; some continue to be improved. New technologies in the form of wave and tidal current generators are being developed.

Although some embodied greenhouse gas emissions will be involved in the manufacture and construction of renewable energy equipment, the life-time emissions from such technologies per unit of energy produced are estimated to be lower than for fossil-fuel derived energy. Renewable energy also has the huge advantage that the fuel is free and not susceptible to price fluctuations, nor imports.

However, nuclear power stations have one big advantage over renewable sources in that in principle they can deliver baseload electricity i.e. the supply that is required to satisfy a demand that exists around the clock. In the twelve months to mid-October 2024 the UK baseload was about 25 GW which is around 60% of the peak demand in the same period.[52]

But in 2023, as already mentioned, nuclear supplied only 13.8% of the demand for electricity, and the installed nuclear capacity is subject to planned power station closures. A national energy supply based predominantly on renewables might struggle, even with a smart grid, to supply the required baseload unless backed up by an efficient form of energy (electricity) storage and strong interconnectivity with other countries.

Finally, many advocate the use of nuclear fusion to generate electricity. Nuclear fusion aims to reproduce the fusion reactions that take place in the Sun. The International Thermonuclear Experimental Reactor (ITER) is being built over 10 years at Cadarache, France, where 35 nations are collaborating to create a fusion reactor. ITER plans to create the project’s First Plasma by 2035 and to reach full fusion power several years after that.[53] ITER is seen as the bridge toward a first plant that will demonstrate the large-scale production of electrical power. This might be a feasible way to generate electricity in the second half of the 21^st century but today, unfortunately, it remains a technology that is unproven at a useful scale.

Conclusions

The UK faces a looming energy gap, when demand will exceed home grown supply, which presently is filled by imported energy. Existing nuclear reactors will mostly be phased out by 2030. Hinkley Point C should be producing electricity by 2030; and construction of Sizewell C has been approved by the government, subject to sufficient funding, which, as of December 2024, has not yet been committed. The government is showing interest in the unproven SMR technology. However, as described above, nuclear power is not renewable nor free of greenhouse gas emissions, nor cheap.

Two possible conclusions can be reached from the above discussion which are at opposite ends of a spectrum of views.

1)       A nuclear energy proponent will argue that one more generation of new nuclear power stations will help to fill the energy gap until renewable energy (or possibly nuclear fusion) is sufficiently developed to take over entirely. It will be particularly important as a supplier of base load, which most renewables can t supply. It will be maintained on the assumption that new uranium reserves will be found, or fuels can be created using the fast breeder fuel cycle. The risks will be considered as worth taking and the argument will emphasise the increasing reliability, safety and security of nuclear power stations, while downplaying the high-level waste disposal problem.

2)       A nuclear energy sceptic will argue that the long time required to plan and construct a new generation of nuclear power stations (some fifteen to twenty years) will be too late to fill the energy gap. In addition, such power stations may come on stream in the UK only as global supplies of uranium fuel start to dry up and/or their exploitation generates more greenhouse gas than gas-fired power stations (the carbon dioxide trap). The argument will be that it seems inescapable that efforts and financial resources would be better spent on expanding existing, well tried, renewable energy technologies, the lifetimes of which will not be constrained by any depletion of their fuel . Lastly, nuclear power carries the risk of serious accidents, will potentially bequeath hazardous waste to thousands of future generations and is open to terrorist attack.

Perhaps, because of the need to decarbonise the grid quickly, the long time required to complete a new nuclear power station, together with the perceived risks, will count against further nuclear energy. Whatever decision is taken, there is an urgent need for a low carbon source of base load power within the next five years.

Bob Whitmarsh, 1 July 2016

Updated 2025 by Brian Shorter