There is much debate currently taking place on the issue of whether or not the UK should build a new generation of nuclear power plant. The debate focuses on two issues: is nuclear (fission) safe and do we actually need nuclear power in the first place.

In this article I will set aside the safety question and instead address why we need nuclear power enough, so much so that the safety question has to be seriously considered and cannot just be dismissed on principle.

Power Interrupted

Power Interrupted by Dave W Clarke

Types of technology

When considering power[1]-generating technology the debate mainly revolves around renewable vs non-renewable technologies. However, from a practical perspective another distinction is important: dispatchable vs non-dispatchable.

Dispatchable generation plant (D) is that which can be turned on when desired by the operator, regardless of external conditions. As will be obvious, the main renewable technologies, wind, marine and solar, fall into the non-dispatchable (ND) category as they cannot guarantee that the conditions they need in order to generate power will be present at any given time.

The reason this distinction is important is because of the nature of electricity and the National Grid. At any given instant the amount of power being put onto, and being taken off, the Grid must be in balance.

A regular supply

If there is an excess of supply or an excess of demand (a shortage of supply) this can manifest in phenomena such as a deviation from the target (50Hz) Grid voltage frequency, power surges and flickering lights. If left unchecked, it can lead to localised blackouts and in the worse case scenario a complete crash of the Grid. An excess of supply can be solved by simply switching off plant. Excess demand can either be addressed by reducing demand (asking factories to close, triggering controlled localised blackouts) or by turning on extra plant.

Ensuring the Grid remains balanced is vital, as modern electrical devices are built to run on a regulated supply and have only a limited ability to withstand power surges. More importantly though, if the Grid were to ever completely crash it is an enormous exercise to restart it.

The best estimate for how long it would take to restore the Grid to full national coverage, assuming no significant damage to the infrastructure was caused when it crashed, is 2-3 days.[2] That would mean 2-3 days of large parts of the country going without electricity. Incidentally, in order to restart the Grid, large D-plant would be required.[3]

ND power plant is problematic in two ways with respect to keeping the Grid balanced. Firstly, ND-plant cannot be relied upon to generate at any given time. For example, in the event of a large anti-cyclone (a prolonged period of very low wind) the entire UK wind fleet (plus a significant part of Europe) could be unavailable for a period of weeks.

More troublesome though is that ND-plant can turn off, or at least reduce output, at any time and without warning. Weather prediction and spreading ND-plant over a wide geographical area can help to mitigate this risk. However for every MW (1 million Watts) of ND power being put onto the Grid a certain amount of D-plant must be kept warm as backup, able to come on-stream quickly in the event that output from the ND-plant drops (the exact amount of backup D power needed for every MW of ND power on the Grid is currently being researched and refined).

Capping the proportion of non-dispatchable generation

As a consequence of this, research indicates that there is a limit to how much power on the Grid at any one time can come from ND sources. A study in Ireland, which can be thought of as a reasonable approximation to mainland UK in terms of electricity infrastructure, indicated that an upper limit of ~40% of power could come from ND sources[4].

If ND power makes up too high a percentage of the total power on the Grid and there is a sudden drop in its output, it will not be possible to bring backup power on-stream quickly enough and there is a higher risk of total Grid failure.

It should be pointed out that National Grid has not yet set a limit on the amount of ND power it will accept. This is most likely because the penetration of ND-plant into the UK market is currently 10% and thus not yet approaching the level where it may need to be limited.

If the proportion of ND power on the Grid at any one time is capped then this will necessarily also cap the amount of energy that ND sources can contribute to the annual UK total. In principle the cap would be at the same percentage, but in practice the intermittent nature of ND generation means that the effective energy cap would be significantly lower than the actual power cap. This is because it would be uneconomical to build ND capacity much greater than the cap level and the capacity that was built would not be running at full output all the time (e.g. in the UK wind turbines only generate electricity for around 3,000 hours a year).

‘D’ Generation

Having established that there will still be a need for significant dispatchable generation in the future UK energy mix we must now consider the types of D-gen available. Technologies proven at large scale are: coal, gas, nuclear, biomass and geothermal.

Of these, biomass and geothermal would also be classed as renewable, however they are also likely to only contribute minimally (<10% of annual energy output combined) in the UK. This leaves the UK needing to generate ~50%+ of its energy from some combination of coal, gas and nuclear even in a scenario where we are heavily exploiting the available renewable resource.

Additionally the Climate Change Committee, a key body for informing UK government policy, has recommended that in order to tackle global warming, by 2030 the carbon intensity of UK electricity generation should be reduced to 50 grams of CO2 emitted per kilowatt hour of electricity generated (g/kWh).[5] The table below shows the typical carbon intensities for various energy generation technologies.[6]



Emissions (g CO2 /kWhe)

Wind 2.5MW Offshore 9
Hydroelectric 3.1MW Reservoir 10
Wind 1.5MW Onshore 10
Solar Thermal 80MW Parabolic Trough 13
Biomass Various Types 14-35
Solar PV Polycrystalline Silicon 32
Geothermal 80MW Hot Dry Rock 38
Nuclear Various Reactor Types 66
Natural Gas Combined Cycle 443 (50 with CCS)
Coal Various Types with Scrubbing 960 (100 with CCS)

If we assume that 50% of UK electricity in 2030 is generated by ND, renewable sources plus biomass and geothermal, at an average CO2 intensity of 15g/kWh, this means the remaining 50% has to be generated by D-gen sources with an average carbon intensity of <85g/kWh.

As can be seen from the table above, this will require a significant proportion of D-gen energy to be generated by either carbon capture and storage (CCS) equipped gas plant or nuclear.

Carbon Capture and Storage

CCS, and especially CCS on gas, is not yet a commercially-proven technology. There are planned demonstration projects aimed at proving the capture technology, however these are unlikely to be operational before 2015.

Additionally, there is a large amount of uncertainty surrounding actually storing the CO2 after it has been captured, with questions remaining over exactly how much storage capacity there is, how sure we can be that the CO2 wont escape and least importantly, though most prominently at present, the rules and regulations governing the storage sites.

All this means that it is highly unlikely that gas-equipped CCS plant will be ready for commercial deployment until 2020, and maybe not until 2025.

With a large amount of older coal, gas and nuclear plant due to close before 2023 the construction program to replace them needs to start well before the 2020-2025 window.[7] Large power plant typically have a lifetime of 25+ years, thus anything we build from now onwards will still be operational in 2030.

Even if we could afford to wait, and gas CCS is technically proven, we would not want to rely on gas as our sole D-gen electricity source as this would expose the UK to a high level of risk from either high gas prices, or worse, an interruption in supplies.


Drawing the arguments presented above to a conclusion, it is clear that, from a technical perspective, the UK needs a new generation of nuclear plant to provide energy security and meet its climate change targets.

There is still a debate to be had over the safety of nuclear power, however that debate must be properly framed by the understanding that there is not a direct trade-off between renewable (ND) technologies and nuclear.

If we choose not to build a new generation of nuclear plant then we will by default be pushed onto a path that, while avoiding the nuclear safety issue, will likely compromise our attempts to tackle global warming.


[1] It is important to properly distinguish between electrical power and energy. Electrical power is the rate at which electrical energy is transferred by a circuit. It is a product of the current and voltage and is measured in Watts (W). Electrical energy measures the power delivered over a period of time. For example, a power of 1 Watt sustained for 1 hour produces an energy of 1 Watt-hour(Wh). In this article when power and energy are referred to it can be assumed that it refers to electrical power and energy.

[2] Local Government Association

[3 ]National Grid

[4] DCENR report

[5] The Renewable Energy Review

[6] NIRS report

[7] Power stations in England (wikipedia)


6 thoughts on “Why We Need Nuclear

  1. FYI: If you reach the point of wanting to understand nuclear (good and bad), you might find my novel ‘Rad Decision,” to be a good resource. It is based on my 20+ years in the US nuclear industry, Not boring, anyway. Just google the title. Free online, no advertisements or sponsors. Best to understand the current generation before moving on to the new ones.

  2. Well written piece! But my concern with nuclear is what is to be done with the waste? I may have missed that in your article if you addressed it. It seems that, that issue is not talked about much in this overall debate.

    • No, you’re quite correct in that I have put the question of nuclear safety and waste handling to one side – I wanted to get across that nuclear power is potentially import enough that those questions have to be properly considered in the context of the dangers of not building more nuclear plant – ie it becomes much harder to tackle global warming.

      My personal is that nuclear waste can be stored safely underground for the timescale required if you properly select the site. Modern reactors produce less waste so quantity is not a problem. I do understand the view of people who feel that the nuclear industry can’t be trusted to behave to the required standard and I think there is an argument to create a UN department with global authority for handling waste (funded by a tax on nuclear producers).

  3. A well researched and in many ways, balanced piece. I have several points though:

    A while ago, I went to a lecture given by Tony Blair’s ex-energy adviser – the Open University Professor of Energy – who said that after pushing ‘energy efficiency’ a lot more, he thought that 50% renewables / 50% coal would be the ideal mix. I tend to agree with him for these reasons:

    Nuclear has lots of ‘hidden carbon’ in the mining & processing of the uranium, the building and decommissioning of the plants, and the storage of the waste.

    As everyone knows, nuclear power also carries phenomenal risks, and the new breed reactors will require the waste (which although smaller, is much more toxic) to be ‘cooled’ in outside ponds for at least 30 years, before being ideally stored underground. Although like CCS, this is still unproven as to whether it would actually work.

    We have hundreds of years supply of coal in the UK, so it’d provide us with near total energy security. While uranium is mined in Russia, Australia etc and there are smaller, finite reserves of it, with ever fluctuating prices.

    Investing in coal power would stimulate UK industries and job creation.

    If we go ahead with new nuclear power plants then how can we legitimately argue that Iran, North Korea etc can’t have nuclear power plants too? ie. Nuclear non-proliferation becomes much harder.

    Asymmetrical warfare is becoming a more prevalent military/terrorist strategy and nuclear power plants are just too big a liability.

    With coal, we’re not locked into such a long lifespan as we are with nuclear power plants.

    Coal is also much cheaper than nuclear, so it’d free up more money to invested into renewables.

    Imagine where renewable energy would be in 10 years, especially with adequate R&D? If you look at geothermal energy for example, it’s potential is only just beginning to be understood. Japan is currently researching ‘seaweed biomass’, which they believe could provide 1/3 or more of their energy needs. The UK has the greatest potential for seaweed biofuel in the world, but this is not being fully considered. Solar energy, although not that efficient in the UK yet, could well be in 10 years. Battery / hydrogen technology is also rapidly improving and could solve some of the issues with intermittent renewable supplies. With large (nuclear power plant size) investments in the above technologies, renewable energy could feasibly begin to provide the D energy you discuss above.

    In short, I think nuclear power is a great option – so long as it’s 90 million miles away and is called the sun. I believe that in times of great need (WWII for example), technology leaps forward, and human creativity and technical skill – if it was truly unleashed – could easily overcome this ‘energy crisis’, as we are indeed completely surrounded by energy. We just need to stop being distracted by looking backwards technologically.

    Nuclear fusion would be a different story though…

  4. Owen,

    Your objections to nuclear power a valid – as stated in a previous reply I think that the waste can be safely handled and that the new reactor types are safe – but accept that this has not been shown beyond doubt and that the questionable ethics of nuclear operators in the past means that they have no goodwill to use as capital in the discussion.

    The world reserves of uranium would be sufficient to sustain a new generation of nuclear fission power plant (and if we need more than one generation of these we’re in big trouble) and there are other nuclear fuels which could be used.

    Coal would give the UK energy security (as, potentially could shale gas – though there are obviously concerns regarding its extraction), though estimates I’ve seen would put the supply at a hundred singular rather than plural. The major problem with coal is that it is the most polluting of energy sources. As I point out in my article, even if 50% of our energy came from renewables the rest would need to be generated by an energy source emitting <85g/kWh of CO2 – CCS equipped coal emits 100g/kWh at 90% capture efficiency (going above 90% is technically and economically challenging). Also, as I point out above, coal equipped CCS will not be ready for commercial deployment quickly enough to meet the coming energy gap.

    Supporting renewables with energy storage is an option. However this makes renewables massively expensive and determining the level of backup needed to ensure the risk of running out of energy is very tricky. Setting the bar too high would be prohibitively expensive while setting it too low would result in energy scares, frequent price distortions and in the worst case a Grid failure. Also, building energy storage to back up renewables would clearly compromise the green credentials of renewable energy (though it would likely still be less than CCS gas).

    All in all I think that it is very unlikely that we will see any more than one or two new coal plant built in the UK and it is possible that none will. The only argument in favour of coal is that of energy security but the environmental and economical drawbacks more than likely outweigh this.

    P.S. Fusion is clearly the great white hope!

    • I agree with what you say concerning the cost/complexities of renewables energy system with storage, and I do believe that at least several nuclear power plants will probably end up getting build because of the reasoning you state above.

      However, if the politicians really wanted to ‘solve’ our problems they would break out of the fractional-reserve banking system which creates an unnecessary shortage of money, destructively limiting our potential.


      We would then finally have enough money to do ‘what is right’, rather than the current cost/benefit analysis which cuts corners and risks destroying the planet and human societies in it’s midst.

      However within the debt paradigm, I believe the most effective course of action would be the large-scale construction of algae biofuel ‘phytotanks’ around coal power plants, utilizing the waste CO2/heat (and some of electrical supply for supplementary light generation). Coal power would then be directly supporting sustainable biofuel production, while the algae would obviously be absorbing the exhaust CO2 after/before CCS. Money could then also be pumped into nuclear fusion research for a long-term energy solution.

      My article on the subject of ‘oilage’ will follow soon – great talking to you.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s