Activities on Climate Technology: Inventory for Nuclear Generation

EXECUTIVE SUMMARY

As a technology which produces virtually no global warming effect, nuclear energy continues to lighten the burden of greenhouse gases on the planet. Between 1.7 and 3.9 billion tonnes of carbon dioxide have been prevented from accelerating the greenhouse effect, through the use over the period 1985-94 of nuclear power plants rather than fossil-fuel plants.

Despite a slowdown in orders for new plants, nuclear has done more in the last decade than ever before to abate the impact of global warming. Three reasons stand out: 

• Older nuclear plants have been upgraded and their output raised.
  

• The amount of time nuclear plants are capable of sending electricity into the grid (their "availability") has been extended.

 These improvements have been made largely by the commercial sector, though with governments and regulatory agencies providing added impetus. They are improvements motivated not by concerns over climate change, but by commercial motives. The felicitous by-product has been greenhouse gas abatement. They hint at the powerful results that could flow from a deliberate policy of adoption of nuclear energy.

THE STIMULUS FOR THE ACTING REPORT FINDINGS

 The seeds of the ACTING study lie in a paper produced by the US Department of Energy’s Energy Information Administration in 1996, "The Voluntary Reporting of Greenhouse Gases". It listed 224 projects, both at the energy consumer’s end (the "demand side") and the energy provider’s (the "supply side").

Demand-side measures included more efficient controls on boilers, and a boost for energy-saving appliances. On the supply side there was a switch to generating electricity from natural gas, and the useful burning-off of gases from landfill garbage sites. Tree-planting projects helped to soak up carbon dioxide, a global warming gas.

But the projects which cut greenhouse gases most radically involved, according to the report, "improving the availability of nuclear plants".

Twenty-one availability improvements were reported by electric utilities as part of their Climate Challenge programme with the US Department of Energy. Each one cut carbon dioxide emissions by over 2 million tonnes per project on average. Some achieved cuts of over 10 million tonnes. And of all these projects, the lion’s share came from nuclear plants.

The US findings encouraged the Nuclear Energy Agency to prepare an OECD-wide survey on nuclear energy’s non-enhancement of the greenhouse effect.

DECOUPLING OF ELECTRICITY OUTPUT AND CARBON DIOXIDE EMISSION RATES

The rate at which electricity generation has yielded carbon dioxide in the OECD countries (1985-1994) has been slowing down. The rate of carbon dioxide release fell back from 0.47 to 0.42 million tonnes per billion units of electricity generated in 1994. Or put another way, 28% more electricity was produced than in 1985, but only 1.15% more carbon dioxide.

Using the same units of measurement for only the countries that generate nuclear power, a reduction from 0.35 to 0.32 emerged. This was despite the fact that relatively few new nuclear plants were brought on line after 1985.

This decoupling of electricity and carbon dioxide outputs has been attributed by an influential and independent third party to the NEA, the International Energy Agency, to nuclear energy. One way of illustrating this decoupling is shown in the following diagram:

Nuclear and Carbon Dioxide Intensity in Selected OECD Countries (gif file, 7 kb)

Overall, over the last nine years between 1.7 and 3.9 billion tonnes of carbon dioxide have been prevented from accelerating the greenhouse effect, through the use of nuclear power plants rather than fossil-fuel plants.

Had there been no nuclear generation, 1.7 billion tonnes would have resulted from gas-burning, or, calculated another way, 3.9 billion tonnes from coal-burning. (Coal gives off more carbon dioxide than gas, quantity for quantity - hence two figures are possible).

The relative contributions of different electricity sources are shown below:

Carbon Dioxide from Electricity Generation (grammes of CO2 equivalent/kWh) (gif file, 6 kb)

The ranges correspond to differences in generation technology for the same primary source.
Source: IAEA-TEC-DOC-892, July 1996.

The emissions arise not just from the process of making electricity, but from all the processes that precede and follow it (mining, refining, fuel manufacture, waste disposal - the entire "fuel cycle" in each case).

HOW NUCLEAR HAS BOOSTED THE DECOUPLING EFFECT

The nuclear sector has brought about carbon dioxide emission cuts in three ways.

First, through new nuclear plants starting up: 99 new plants came on stream in the 1985-94 period, creating 96 million kilowatts of new capacity.

Second, through increases in output from plants already running: plant capacities were raised by 3.13 million kilowatts at 36 nuclear plants in six countries.

And third, through the greater "availability" of plants made possible by more efficient maintenance work and fewer unplanned stoppages: the availability factor rose from 72.5% to 79.5% on average, an improvement alone saving the release of 700 million tonnes of carbon dioxide.

POTENTIAL FOR MORE GREENHOUSE GAS SAVINGS FROM NUCLEAR ENERGY

Two tendencies will weigh in the balance as the potential unfolds for nuclear energy to help abate greenhouse warming.

On the one hand, the root causes for slower or halted nuclear construction in some countries will continue, either because they have enough round-the-clock ("baseload") electricity plant to hand and need no more, or because they are building gas-fired power stations which, on account of cheap fuel and rapid build times, generate electricity particularly competitively.

On the other hand, estimates of the costs of power stations brought on line soon after 2000 show that, where nuclear energy is not competitive, a hike of 25% in the price of gas or other fossil fuels - which can be the consequence of balancing supply with demand or of policy decisions or situations - would make nuclear the cheapest source of electricity.

Then there is scope for nuclear plants to produce more electricity ("capacity upgrades" ). The upgrades carried out so far have led to increases in capacity of between 5% and 10%, with plans for 15% in some cases. If increases of that size were carried out on all the 320 nuclear plants in OECD countries not yet upgraded - though it may not be worthwhile or possible to upgrade every last reactor, notably older ones - the carbon dioxide savings would be considerable, at an estimated 180 million tonnes.

Then again, further scope for savings is expected to flow from the trend towards greater plant availability (a measure of how much of the time the plant is capable of being run to generate electricity). In 1994 there were still nuclear plants, 97 million kilowatts’ worth of capacity in fact, which had an average availability of only 59%. This was rather below the lowest country average of 77.6%, and well below the 85% comfortably and consistently achieved in some countries. If all the plants with a 59% rating could have it raised to 75%, 68 million tonnes a year of carbon dioxide would no longer need to be released into the atmosphere by the burning of fossil fuels.

CONCLUSION

It is clear that for the moment nuclear plants are being built only in countries which have extremely limited energy sources of their own, and so experience special anxieties about secure energy supplies. But even without large expansion programmes, nuclear energy is being spurred on, by a combination of government exhortation and commercial pressure, to raise still further its contribution to greenhouse gas abatement, and to ease the potential damage to the global climate. It is not the only way of replacing base-load electricity production from fossil fuels but in OECD countries it has proved its technical merits, contributing 24% of electricity supply.