- Energy resources are available to supply the world's expanding needs without environmental detriment.
- Wastes remain a major consideration whether they are released to the environment or not.
- Ethical principles seem increasingly likely to influence energy policy in many countries, which augurs well for nuclear energy.
- The competitive position of nuclear energy "is robust from a sustainable development perspective since most health and environmental costs are already internalised."1
Until about 30 years ago, energy sustainability was thought of simply in terms of availability relative to the rate of use. Today, in the context of the ethical framework of sustainable development, including particularly concerns about global warming, other aspects are also very important. These include environmental effects and the question of wastes, even if they have no environmental effect. Safety is also an issue, as well as the broad and indefinite aspect of maximising the options available to future generations. Geopolitical questions of energy security are central to the assessment of sustainability for individual countries, along with the affordability of the electricity produced.
Sustainable development criteria have been pushed into the front line of energy policy. In the light of concerns about climate change due to apparent human enhancement of the greenhouse effect, there is growing concern about how we address energy needs on a sustainable basis.
A number of factors are widely agreed. The world's population will continue to grow for several decades at least. Energy demand is likely to increase even faster, and the proportion supplied by electricity will also grow faster still. However, opinions diverge as to whether the electricity demand will continue to be served predominantly by extensive grid systems, or whether there will be a strong trend to distributed generation (close to the points of use). That is an important policy question itself, but either way, it will not obviate the need for more large-scale grid-supplied power, especially in urbanised areas, over the next several decades. Much demand is for continuous, reliable supply of electricity on a large scale, and this qualitative consideration will continue to dominate.
The key question is how we generate that electricity. Today, worldwide, 68% comes from fossil fuels (41% coal, 21% gas, 5.5% oil), 13.4% from nuclear fission and 19% from hydro and other renewable sources. There is no prospect that we can do without any of these (though oil has a more vital role in other applications).
Sources of energy
Harnessing renewable energy such as wind and solar is an appropriate first consideration in sustainable development, because apart from constructing the plant, there is no depletion of mineral resources and no direct air or water pollution. In contrast to the situation even a few decades ago, we now have the technology to access wind on a significant scale for electricity, and with some subsidy on a minority of supply being from those sources, they are affordable. But harnessing these 'free' sources cannot be the only option. Renewable sources other than hydro – notably wind and solar – are diffuse, intermittent, and unreliable by nature of their occurrence. These aspects offer a technological challenge of some magnitude, given that electricity cannot be stored on any large scale. For instance, solar-sourced electricity requires collecting energy at a peak density of about 1 kilowatt (kW) per square metre when the sun is shining to satisfy a quite different kind of electricity demand – one which mostly requires a relatively continuous supply.
Wind is the fastest-growing source of electricity in many countries, and there is a lot of scope for further expansion. While the rapid expansion of wind turbines in many countries has been welcome, capacity is seldom more than 30% utilised over the course of a week or year, which testifies to the unreliability of the source and the fact that it does not and cannot match the pattern of demand. Wind is intermittent, and when it does not blow, back-up capacity such as hydro or gas is needed. When it does blow, and displaces power from other sources, it reduces the economic viability of those sources and hence increases prices.
The rapid expansion of wind farms and solar power capacity is helped considerably by generous government-mandated grants, subsidies and other arrangements ultimately paid for by consumers. Where the financial inducements to build wind and solar capacity result in a strong response however, the subsidies become unaffordable and are now being cut back in many countries. Also there is often a strong groundswell of opposition on aesthetic grounds from the countryside where wind turbines are located.
Renewable sources such as wind and solar are intrinsically unsuited to meeting the demand for continuous, reliable supply on a large scale – which comprises most demand in developed countries.
A fuller treatment of electricity from renewable sources is in the information page on Renewable Energy and Electricity.
Apart from renewables, it is a question of what is most abundant and least polluting. Today, to a degree almost unimaginable even 30 years ago, there is known to be an abundance of many energy resources in the ground. Coal and uranium (not to mention thorium) are available and unlikely to be depleted this century.
The criteria for any acceptable energy supply will continue to be cost, safety, and security of supply, as well as environmental considerations. Addressing environmental effects usually has cost implications, as the current climate change debate makes clear. Supplying low-cost electricity with acceptable safety and low environmental impact will depend substantially on developing and deploying reasonably sophisticated technology. This includes both large-scale and small-scale nuclear energy plants, which can be harnessed directly to industrial processes such as hydrogen production or desalination, as well as their traditional role in generating electricity.
IAEA classification of nuclear energy scenario sustainability
- Level 1. Safe, secure, economical and publicly acceptable nuclear power with security of supply – addresses conditions necessary for newcomers to deploy nuclear energy.
- Level 2. Safe disposal of all nuclear wastes in a complete once-through fuel cycle with thermal reactors and with retrievable spent nuclear fuel disposal. Level 2 addresses political issue of 'solving the waste problem'. Retrievability is required to not limit future generations’ options.
- Level 3. Initiate recycling of used nuclear fuel to reduce wastes. Limited recycle that reduces high-level waste volumes, slightly improves U utilisation, and keeps most of the U more accessible (Depleted U and Recovered U/Th). A branch of Level 3 is a once-through breed and burn option, providing significant improvement in resource utilization (up to 10 times).
- Level 4. Guarantee nuclear fuel resources for at least the next 1000 years via complete recycle of used fuel. Closed fuel cycle with breeding of fissile material (from 238U or 232Th) to improve natural resource utilisation by a factor of 10 to 100. Solves the resource utilisation issue by providing fuel for thousands of years while also significantly reducing long-lived radioactivity burden (Pu-233/U recycle).
- Level 5. Reduce radiotoxicity of all wastes below natural uranium level. Closed fuel cycle recycling all actinides and only disposing fission products to minimise long-term radiotoxicity of nuclear waste. Achieves additional substantial reduction of long-lived radioactivity burden (Pu-233/U/minor actinide recycle) and reduces radiotoxicity of waste down to natural uranium levels within 1000 years. As an option, transmutation of long-lived fission produces could be considered to further reduce waste radiotoxicity.
Is nuclear energy renewable?
Generally 'renewable' relates to harnessing energy from natural forces which are renewed by natural processes, especially wind, waves, sun and rain, but also heat from the Earth's crust and mantle. Although it shares many attributes with technologies harnessing these natural forces – for instance radioactive decay produces much of the heat harnessed geothermally – nuclear power is usually categorised separately from ‘renewables’.
Conventional nuclear power reactors do use a mineral fuel and demonstrably deplete the available resources of that fuel. In such a reactor, the input fuel is uranium-235 (U-235), which is part of a much larger mass of uranium – mostly U-238. This U-235 is progressively 'burned' to yield heat. But about one-third of the energy yield comes from something which is not initially loaded in: plutonium-239 (Pu-239), which behaves almost identically to U-235. Some of the U-238 turns into Pu-239 through the capture of neutron particles, which are released when the U-235 is 'burned'. So the U-235 used actually renews itself to some extent by producing Pu-239 from the otherwise waste material U-238.
This process can be optimised in fast neutron reactors, which are likely to be extensively deployed in the next generation of nuclear power reactors. A fast neutron reactor can be configured to 'breed' more Pu-239 than it consumes (by way of U-235 + Pu-239), so that the system can run indefinitely. While it can produce more fuel than it uses, there does need to be a steady input of reprocessing activity to separate the fissile plutonium from the uranium and other materials discharged from the reactors. This is fairly capital-intensive but well-proven and straightforward. The used fuel from the whole process is recycled and the usable part of it increases incrementally.
As well as utilizing about 60 times the amount of energy from uranium, fast neutron reactors will unlock the potential of using even more abundant thorium as a fuel (see information page on Thorium). Using a fast neutron reactor, thorium produces U-233, which is fissile. This process is not yet commercialised, but it works and if there were ever a pressing need for it, development would be accelerated. India is the only country concentrating on this now, since in a world context uranium is so abundant and relatively cheap. In addition, some 1.5 million tonnes of depleted uranium now seen by some people as little more than a waste, becomes a fuel resource. The consequence of this is that the available resource of fuel for fast neutron reactors is so plentiful that under no practical terms would the fuel source be significantly depleted.
Regardless of the various definitions of 'renewable', nuclear power therefore meets every reasonable criterion for sustainability, which is the prime concern.
There is abundant coal in many parts of the world, but with the constraints imposed by concern about global warming, it is likely that this will increasingly be seen as chemical feedstock and its large-scale use for electricity production will be scaled down. Current proposals for 'clean coal' technologies may change this outlook. The main technology involves the capture and subsequent storage of the carbon dioxide from the flue gas. Elements of the technology are proven but the challenge is to actually commercialize it and bring the cost down sufficiently to compete with nuclear power.
Natural gas is also reasonably abundant, especially with the advent of technologies for tapping that in coal seams and shales, but is so valuable for direct use after being reticulated to the point where heat is required, and as a chemical feedstock, that its large-scale use for power generation makes little sense and is arguably unsustainable. However, while abundant supply keeps prices down in the short to medium-term, it is the most economical means of generating electricity in some places, notably North America.
Fuel for nuclear power is abundant, and uranium is even available from sea water at costs which would have little impact on electricity prices. Furthermore, if well-proven but currently uneconomic fast neutron reactor technology is used, or thorium becomes a nuclear fuel, the supply is almost limitless. (See information page on Supply of Uranium.)
The hydrogen economy
Someday, hydrogen is expected to come into great demand as a transport fuel which does not contribute to global warming. It may be used in fuel cells to produce electricity or directly in internal combustion motors – as experimentally now.
Fuel cells are at an early stage of technological development and still require substantial, research and development input, although they are likely to be an important technology in the future.
Hydrogen may be provided by steam reforming of natural gas (in which case the emission of by-product CO2 has to be taken into account), by electrolysis of water, or (in future) by thermochemical processes using nuclear heat. Today, about 96% of hydrogen is made from fossil fuels: half from natural gas, 30% from liquid hydrocarbons and 18% from coal. This gives rise to quantities of carbon dioxide emissions - each tonne produced gives rise to 11 tonnes of CO2.
Some new types of nuclear reactor such as high-temperature gas cooled reactors (HTRs), operating at around 950°C have the potential for producing hydrogen from water by thermochemical means, without using natural gas, and without any CO2 arising.
Large-scale use of electrolysis would mean a considerable increase in electricity demand. However, this need not be continuous baseload supply, as hydrogen can be accumulated and stored, and solar or wind generation may well serve this purpose better than supplying consumer electricity demand.
However, pending the development of affordable mass-produced fuel cells, a significant increase in base-load electricity demand may result from the adoption of plug-in electric hybrid vehicles and full electric vehicles (see information page on Electricity and Cars). These are on the threshold of commercial availability (today's hybrid vehicles only need bigger battery capacity and the facility to use mains power for recharging).
Wastes – both those produced and those avoided – are a major concern in any consideration of sustainable development.
Burning fossil fuels produces primarily carbon dioxide as waste, which is inevitably dumped into the atmosphere. With black coal, approximately one tonne of carbon dioxide results from every thousand kilowatt hours generated. Natural gas contributes about half as much CO2 as coal from actual combustion, and also some (including methane leakage) from its extraction and distribution. Oil and gas burned in transporting fossil fuels adds to the global total. As yet, there is no satisfactory way to avoid or dispose of the greenhouse gases which result from fossil fuel combustion.
Nuclear energy produces both operational and decommissioning wastes, which are contained and managed. Although experience with both storage and transport over half a century clearly shows that there is no technical problem in managing any civil nuclear wastes without environmental impact, the question has become political, focussing on final disposal. In fact, nuclear power is the only energy-producing industry which takes full responsibility for all its wastes, and costs this into the product – a key factor in sustainability.
Ethical, environmental and health issues related to nuclear wastes are topical, and their prominence has tended to obscure the fact that such wastes are a declining hazard, while other industrial wastes retain their toxicity indefinitely.
Regardless of whether particular wastes remain a problem for centuries or millennia or forever, there is a clear need to address the question of their safe disposal. If they cannot readily be destroyed or denatured, this generally means that they need to be removed and isolated from the biosphere. This may be permanent, or retrievable.
An alternative view asserts that indefinite surface storage of high-level wastes under supervision is preferable. This may be because such materials have some potential for recycling as a fuel source, or negatively because progress towards successful geological disposal would simply encourage continued use and expansion of nuclear energy. However, there is wide consensus that dealing effectively with wastes to achieve high levels of safety and security is desirable in a 50-year perspective, ensuring that each generation deals with its own wastes.
According to the OECD's Nuclear Energy Agency: "The scientific and technical community generally feels confident that there already exist technical solutions to the spent fuel and nuclear waste conditioning and disposal question. This is a consequence of the many years of work by numerous professionals in institutions around the world... There is a wide consensus on the safety and benefits of geologic disposal."2
Ethical aspects of nuclear wastes
In a 1999 OECD article3, Claudio Pescatore outlines some ethical dimensions of this question. He starts on a very broad canvas, quoting four fundamental principles proposed by the US National Academy of Public Administration4:
- Trustee Principle: Every generation has obligations as trustee to protect the interests of future generations.
- Sustainability Principle: No generation should deprive future generations of the opportunity for a quality of life comparable to its own.
- Chain of Obligation Principle: Each generation's primary obligation is to provide for the needs of the living and succeeding generations. Near-term concrete hazards have priority over long-term hypothetical hazards.
- Precautionary Principle: Actions that pose a realistic threat of irreversible harm or catastrophic consequences should not be pursued unless there is some compelling, countervailing need to benefit either current or future generations.
These four principles resulted from a request by the US Government to elucidate principles for guiding decisions by public administrators on the basis of the international Rio and UNESCO Declarations5 which acknowledge responsibilities to future generations. The principles can be applied to the question of nuclear wastes, and in particular to their deep geological disposal, a system with inherent passive safety. Referring to relevant 1995 IAEA and NEA publicationsa, Dr Pescatore summarises the principles in this context as follows:
- The generation producing the waste is responsible for its safe management and associated costs.
- There is an obligation to protect individuals and the environment both now and in the future.
- There is no moral basis for discounting future health and risks of environmental damage.
- Our descendants should not knowingly be exposed to risks which we would not accept today. Individuals should be protected at least as well as they are at present.
- The safety and security of repositories should not presume a stable social structure for the indefinite future or continued technological progress.
- Wastes should be processed so they will not to be a burden to future generations. However, we should not unnecessarily limit the capability of future generations to assume management control, including possible recovery of the wastes.
- We are responsible for passing on to future generations our knowledge concerning the risks related to waste.
- There should be enough flexibility in the disposal procedures to allow alternative choices. In particular information should be made available so the public can take part in the decision-making process which, in this case, will proceed in stages.
Deep geological disposal is considered as the final stage in waste management. It should ensure security and safety in a way that will not require surveillance, maintenance, or institutional control.
Some energy sources dispose of wastes to the environment or have health effects which are not costed into the product. These implicit subsidies, or external costs as they are generally called, are nevertheless real and usually quantifiable, but are borne by society at large. Their quantification is necessary to enable rational choices of energy sources. Nuclear energy has always provided for waste disposal and decommissioning costs in the actual cost of electricity (ie it has internalised them), so that external costs are minimal.
The External costs of Energy (ExternE) European Research Network has compared the external costs of various means of generating electricityb. It showed that coal has the highest external costs (and about the same for all other generation costs), followed by gas, while nuclear and wind were one tenth or less of coal. The methodology included the risk of accidents and covered full fuel cycle. Hence if external costs are taken into account, nuclear energy is shown as very competitive.
The safety of nuclear energy has been well demonstrated, notwithstanding the continued operation of a small number of reactors which are, by western standards, distinctly unsatisfactory. These include two old Soviet designs, one of which – before some very extensive modifications to the type – precipitated the 1986 Chernobyl disaster. Over 14,500 reactor-years of operation have shown a remarkable lack of problems in any of the reactors which are licensable in most of the world. The only serious accident to a Western plant in over 30 years was that precipitated by an unprecedented tsunami at Fukushima in March 2011. Even then, and despite massive inconvenience to many people due to evacuation, the lack of human casualties from the accident contrasted with some 25,000 killed by the actual tsunami.
There is probably no other large-scale technology used worldwide with a comparable safety record. This is largely because safety was given a very high priority from the outset of the civil nuclear energy program, at least in the West. The safety provisions include a series of physical barriers between the hot radioactive reactor core and the environment, and the provision of multiple safety systems, each with back-up, and designed to accommodate human error. Safety systems, in the sense of back-ups and containment, account for a substantial part of the capital cost of nuclear power reactors - a higher proportion even than in aircraft design and construction.
Any statistics comparing the safety of nuclear energy with alternative means of generating electricity show nuclear to be the safest. In fact, Chernobyl and Fukushima are the only blemishes on the record, and Chernobyl is of very little relevance to the safety of most of the world's reactors.
From a national perspective, the security of future energy supplies is a major factor in assessing their sustainability. Whenever objective assessment is made of national or regional energy policies, security of supply is a priority.
France's decision in 1974 to expand dramatically its use of nuclear energy was driven primarily by considerations of energy security. However, the economic virtues have since become more prominent. Various EU reports over the last decade have highlighted the importance of nuclear power for Europe's energy security and climate goals. Many governments are clear that nuclear energy must play an increasing role by 2030, and in recent years the formerly rather negative UK government has been foremost in declaring this.
Nuclear energy and renewables have one important feature in common. They give us access to virtually limitless resources of energy with negligible opportunity cost – we are not depleting resources useful for other purposes, and we are using relatively abundant rather than less abundant energy. We can envisage a time when fossil carbon-based fuels will be too valuable to burn on the present scale.
Recent analyses fail to come up with any 50-year scenario based on sustainable development principles which does not depend significantly on nuclear fission to provide large-scale, highly intensive energy, along with renewables to meet some small-scale (and especially dispersed) low-intensity needs. The alternative is either to squander fossil carbon resources or deny the aspirations of hundreds of millions of people in the next generation.
Alternative low-CO2 means of producing base-load electricity have not been credibly proposed, and wildly unrealistic projections for renewables of a few years ago have tended to become muted. Certainly all the reputable energy scenarios show the main load being carried by coal, gas, and nuclear, with the share between them depending on economic factors in the context of various levels of CO2 emission constraints.
As the notion of sustainability is increasingly supported politically, all external costs are likely to be factored in, thus affecting the economic choices among fuels for electricity generation in nuclear power's favour.
There is now sufficient solar and wind capacity operating on grid systems for their advantages and limitations to be widely evident. That will help focus public discussion on the real options for continuous, reliable (baseload) electricity generation on the large scale required. Nuclear power can – and must – contribute significantly to sustainable development.