Sustainable Energy

(February 2008)

Energy resources are available to supply mankind's expanding needs without environmental detriment.
Wastes remain a major concern whether they are released to the environment or not.
Ethical principles seem increasingly likely to dominate energy policy in many countries, which augurs well for nuclear energy.
"When viewed from a large set of criteria, nuclear power shows a unique potential as a large scale sustainable energy source." OECD 2001.
"The competitive position of nuclear energy is robust from a sustainable development perspective since most health and environmental costs are already internalised." OECD 2001.

Until the last ten or twenty years sustainable energy 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, other aspects are equally 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.
Sustainable Development criteria have been pushed into the front line of energy policy. In the light of concerns about global warming due to human enhancement of the greenhouse effect, there is clearly growing concern about how we address energy needs on a sustainable basis.

Energy demand

A number of factors are indisputable. 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, and this qualitative consideration will continue to dominate.

The key question is how we generate that electricity. Today, worldwide, 64% comes from fossil fuels, 16% from nuclear fission and 19% from hydro, with very little from other renewables. There is no prospect that we can do without any of these.

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. 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. The very fact that we seek the sun for our summer holidays testifies to its low intensity. Similarly, bad weather and night-time underline its short-term unreliability. These two aspects offer a technological challenge of some magnitude. It 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 requires a relatively continuous supply.

Wind is the fastest-growing source of electricity in many countries, albeit from a low base, and there is a lot of scope for further expansion. While it has been exciting to see the rapid expansion of wind turbines in many countries, capacity is seldom more than 30% utilised over the course of a year, which testifies to the unreliability of the source and the fact that it does not and cannot match the pattern of demand. The rapid expansion of wind farms is helped considerably by generous government-mandated grants, subsidies and other arrangements ultimately paid by consumers. But there is often a strong groundswell of opposition on aesthetic grounds from the countryside where the 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.

Apart from renewables, it is a question of what is most abundant and least polluting. Today, to a degree almost unimaginable even 25 years ago, there is an abundance of many known 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 and safety, as well as environmental considerations. Addressing environmental effects usually has cost implications, as the current greenhouse 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.

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. And because it shares many attributes with technologies harnessing these natural forces - for instance radioactive decay produces much of the heat harnessed geothermally, nuclear energy is sometimes classified with them.
But there are other reasons to call nuclear energy "renewable". In any nuclear reactor the input fuel is normally uranium-235 (U-235) which is part of a much larger mass of uranium - mostly U-238. This U-235 is progressively 'burned' over about three years to yield a lot of 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. This is because the fission of U-235 causes some of the U-238 to turn into Pu-239, so about half of the U-235 used actually renews itself by producing Pu-239 from the otherwise waste material U-238. So, it's partly Renewable in this situation.
This raises the possibility of whether U-235 can be made fully Renewable. In fact, it can, by optimising the process in another kind of reactor which 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 steady input of reprocessing activity to separate the fissile plutonium from the uranium and other materials. This is fairly capital-intensive but well-proven and basically straightforward. The used fuel from the whole process is recycled and the usable part of it increases incrementally.
Apart from this there is thorium, which is four times as abundant as uranium. Using a similar process to the breeder reactor, thorium can produce 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 uranium is so abundant and relatively cheap.

Energy resources

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 using the coal to make hydrogen from water by a two-stage gasification process, then burying the carbon dioxide and burning the hydrogen. Elements of the technology are proven but the challenge is to bring the cost down sufficiently to compete with nuclear power.

Natural gas is also reasonably abundant 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.

Fuel for nuclear power is abundant, and if well-proven but currently uneconomic fast breeder technology is used, or thorium becomes a nuclear fuel, the supply is almost limitless.

Uranium is even available from sea water at costs which would have little impact on electricity prices. In any case the resource can be multiplied 60- to one hundred-fold by adopting the kind of technology which our postwar forebears thought would be necessary by now - fast neutron reactors used as breeders - See also paper 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 will be an important technology in the future.

Hydrogen may be provided by steam reforming of natural gas (in which case CO₂ has to be taken into account), by electrolysis of water, or by thermochemical processes using nuclear heat.

Some new types of nuclear reactor such as high-temperature gas cooled reactors, operating at around 950-1000°C have the potential for producing hydrogen from water by thermochemical means, without using natural gas.

Large-scale use of electrolysis would mean a considerable increase in electricity demand. However, this need not be continuous base-load supply, as hydrogen can be accumulated and stored, and solar or wind generation may well serve this purpose better than supplying consumer electricity demand.

Wastes

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 as coal from actual combustion, and also some (including methane leakage) from its distribution. Oil and gas burned in transport 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 wastes

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 wastes under supervision is preferable because progress towards successful geological disposal would simply encourage continued use and expansion of nuclear energy. This however is simply another case where ideological opposition to nuclear energy is more important to its detractors than dealing effectively with wastes to achieve high levels of safety and security, and further, ensuring that each generation deals with its own wastes. The wider question of alternative low-CO₂ means of producing base-load electricity tends not to be addressed, beyond wildly unrealistic projections for renewables.

"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 many years work by numerous professionals in institutions around the world. .... There is a wide consensus on the safety and benefits of geological disposal." OECD 2001.

Ethical aspects of nuclear wastes

In a 1999 OECD article, Long-term management of radioactive waste, ethics and the environment, 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 Administration. They 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 Declarations which acknowledge responsibilities to future generations:

The Trustee Principle: "Every generation has obligations as trustee to protect the interests of future generations".
The Sustainability Principle: "No generation should deprive future generation of the opportunity for a quality of life comparable to its own."
The Chain of Obligation Principle: "Each generation's primary obligation is to provide for the needs of the living and succeeding generations," the emphasis being that "near-term concrete hazards have priority over long-term hypothetical hazards."
The Precautionary Principle: "Actions that pose a realistic threat of irreversible harm or catastrophic consequences should not be pursued unless there is some countervailing need to benefit either current or future generations."

These can be applied to the question of nuclear wastes, and in particular to their geological disposal, a system with inherent passive safety. Referring to relevant 1995 IAEA and NEA publications, 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.

Dr Pescatore points out that 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.

External costs

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 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 cost of electricity.

The 2001 ExternE study in Europe compared the external costs of various means of generating electricity. It showed that coal was highest (and about the same as 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 becomes very competitive.

Safety

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 12,000 reactor-years of operation have shown a remarkable lack of problems in any of the reactors which are licensable in most of the world.

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. About one third of the cost of a typical reactor is due to its safety systems and structures, including containment and back-up provisions. This is 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 is the only blemish on a near perfect record, and is of very little relevance to the safety of most of the world's reactors.

Energy security

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 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. The EU Green Paper on energy security in 2000 put forward coal, nuclear energy and renewables as three pillars of future energy security for Europe and EU leaders have since highlighted the importance of nuclear power for Europe's energy security and climate goals. The US and UK governments are clear that nuclear energy must play an increasing role this century.

Opportunity costs

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. Probably the time is approaching when fossil carbon-based fuels will be too valuable to burn on the present scale. Of course minimising opportunity cost would be very difficult if we preferred to "leave uranium in the ground", as sometimes urged.

Outlook

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 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.

Nuclear energy's detractors have yet to credibly suggest how most of future electricity should be produced. Certainly all the reputable energy scenarios show the main load being carried by coal, gas, and nuclear, with the balance among them depending on economic factors in the context of various levels of greenhouse constraints.
As the notion of sustainability is increasingly supported politically, all external costs are likely to be factored in. Then it will start to drive the economic choices among fuels for electricity generation.
There is now sufficient solar and wind capacity operating on grid systems for their advantages and limitations to become widely evident. That will help focus public discussion on the real options for continuous, reliable (base-load) electricity generation on the large scale required. Nuclear power can contribute significantly to sustainable development.

Sources:
OECD NEA Newletter #1/99
OECD IEA, 2006 & 2007, World Energy Outlook.
OECD NEA, 2000, Nuclear Energy in a Sustainable Development Perspective.
IAEA, 1997, Sustainable Development and Nuclear Power.
World Energy Council, 2000, Energy for Tomorrow's World - Acting Now!
World Energy Council 2002 statement.
OECD NEA 2001, Trends in the Nuclear Fuel Cycle.