Is nuclear power the key to finally reducing the CO2 footprint?

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BY GILLES YOUINOU

GERMANY is eager to do its part and aims to lower its CO2 footprint with aggressive development of wind and solar, while, in parallel, phasing out nuclear. In about 20 years, at a cost of at least two hundred billion dollars, it has added about 80 gigawatts of wind and solar generating capacity—enough in principle to cover its winter peak—to its energy mix, an amazing feat in itself. Wind turbines and solar panels are highly visible and highly advertised. However, the question remains—do they really lower the CO2 emissions of their power sector?

In its 2013 report, “CO2 Emissions from Fuel Combustion,” the International Energy Agency shows that the amount of CO2 generated per kWh of electricity in Germany is still about 480 grams, despite their large investment in wind and solar technology. The reason is that the country still relies on coal and natural gas for about half of its electricity, as its wind and solar fleet lay idle most of the time. In the meantime, France—which relies on nuclear power for 75 per cent of its electricity—generated only about 70 grams of CO2 per kWh.

When France decided to go nuclear after the first oil shock in 1973, it derived about two thirds of its power from coal and oil-fired power plants and emitted 500 grams of CO2 per kWh. Twenty five years later, its power sector was almost carbon-free.

Because of its reliance on nuclear power, France currently has one of the lowest rates of CO2 emissions per kWh in Europe. Every year, the French power sector emits approximately 260 million fewer tonne (metric ton) of CO2 than its German counterpart, despite similar productions (respectively 560 billion kWh and 630 billion kWh). This is equivalent to taking 175 million cars off the road (assuming an average emission of 0.15 kg-CO2 per car and per km and 10,000 km per car and per year)—about 75 per cent of the whole European fleet of personal vehicles.

Getting rid of CO2 from the power sector is feasible; France—the world’s 6th largest economy—did it in 25 years. Getting rid of nuclear is of course also feasible, the easiest way being to replace it by coal or gas. Unless large bodies of water are available to store energy—such as in Norway for example—getting rid of both is more difficult because it requires gigawatt-scale energy storage systems and billion-tonne-per-year carbon capture and storage systems that are currently not available.

To have a chance of being successful with its energy transition, Germany needs to greatly expand its already large wind and solar fleet and build new back-up gas turbines as well as energy storage systems. The resulting over-capacity will significantly challenge current economic and market paradigms. By 2050, if everything goes well, they hope to reach the same level of CO2 emissions per kWh as France today.

Energy storage, the missing link

Only a successful deployment of environmentally friendly, cost effective, gigawatt-scale energy storage systems would allow wind and solar to generate, in principle, up to 100 percent of the world electricity. It would be a real game changer, but basing an energy plan around the hope for major technology breakthroughs in this area entails significant risks.

The only large scale energy storage technology currently available is based on pumping large volumes of water to a higher elevation—this technology while affordable and relatively benign, is unfortunately limited by the availability of appropriate sites.

Without large energy storage systems, wind and solar could still, in principle, generate of the order of 25 per cent of the world’s electricity. This would require a combined wind and solar fleet of at least 5,000 gigawatts, about 10 times the current capacity. Other reliable and flexible—low-carbon if possible—energy sources would still be needed for the other 75 per cent.

Note that, as a matter of policy, well-intentioned though it may be, wind and solar operators are currently not responsible for the consequences that the intermittent outputs of their plants have on the grid, the other operators are; wind and solar promoters advocate that the grid must become more flexible to accommodate larger and larger wind and solar penetration which, as long as grid scale energy storage is not available, is also another way of asking that this practice should be maintained.

The fuel economy of coal and gas power plants drops when they have to ramp their power up and down to make up for the intermittent nature of wind and solar generation. A careful accounting of these various effects will be required to ensure that the introduction of large quantities of wind and solar power will actually lead to the expected reductions in CO2 emissions. To make energy systems based on wind and solar—as well as on gas and coal for back-up—low-carbon, carbon capture and storage will likely need to be implemented.

Small scale demonstrations have been done, but there are still large uncertainties regarding the viability of sites capable of storing billions of tonnes of CO2.

Delays in implementation caused by legal and regulatory issues—in particular those associated with long-term liability—are likely when it comes to choosing the sites that will have to permanently host billions of tonnes of CO2. Such delays have been happening for the geological disposal of used nuclear fuel. However, unlike used nuclear fuel, which can be safely stored at reactor sites while waiting for a final disposal solution, CO2 is currently released to the atmosphere until a final solution emerges—which could take a while.

The nuclear option

Emotions run high when it comes to nuclear power, but with large uncertainties regarding the feasibility of the needed large-scale low-carbon enabling technologies—gigawatt-scale energy storage systems and billion-tonne-per-year carbon capture and storage systems—it is worth considering nuclear as another possible low-carbon energy source.

In order to make rational choices, it is important not to confuse the consequences of an event and the risk associated with that event. Risk is the product of the consequence by the probability that this particular event happens. For example, a large meteorite colliding with our planet could potentially annihilate most life, but the probability that it happens is very small, so overall, the risk is also very small. A nuclear reactor accident can also potentially have dramatic consequences, such as the long term displacement of large populations and the psychological distress that goes with it. Accidents of such severity are, however, very rare. Nonetheless, a large fraction of the public feels differently and perception is a fundamental parameter of the equation.

After more than two decades spent analysing available data, experts from institutions such as the World Health Organisation and the United Nations Environment Programme, concluded that 43 people died of causes directly attributable to the Chernobyl accident.

They also indicate a potential 3 per cent increase in cancer mortality in the 600,000 most exposed people. In such a large population, unfortunately, more than 120,000 lethal cancers are expected to occur spontaneously—independently of any radiation exposure—and the Chernobyl accident may add 4,000 cases to this macabre toll. However, a long standing issue associated with this predicted increase is that it cannot be verified with certainty because it is much smaller than—and mostly undistinguishable from—the background of spontaneous cancers. The same organisations have been involved in the assessment of the consequences of the Fukushima accident; the consensus is now that cesium and iodine—the two most troublesome elements—releases were no more than, respectively, one-half and one-fourth of those of Chernobyl. No one was killed by the radiations and no long term effects are expected among the evacuated people. However, for both Chernobyl and Fukushima, the main concern is related to the clean-up of the areas which were contaminated with radioactive materials. It can take decades and cost billions of dollars to ensure that the residual level of radiation is low enough—comparable to the level of natural radiation—for the population to move back.

The statistics regarding the effects of air pollution—a problem that nuclear helps lessening—is useful. A recent publication from the World Health Organisation states that “outdoor air pollution in both cities and rural areas was estimated to cause 3.7 million premature deaths world-wide in 2012.” The International Agency for Research on Cancer also announced recently that “it has classified outdoor air pollution as carcinogenic to humans” and that “the most recent data indicate that in 2010, 223,000 deaths from lung cancer worldwide resulted from air pollution.”

Finally, whereas most of the general public will very likely point at the Chernobyl and Fukushima accidents as the worst modern science and engineering failures, only very few will remember the 1975 collapse of the Banqiao dam (China) where approximately 26,000 people died from flooding and another 145,000 died because of epidemics and famine.

Another dam, Machchu-2, in India also failed a few years later (1979) killing at least 2,000 people. Experience shows that nuclear power does not entail more risk than other industries.

Used fuel disposal

Technical solutions exist and the management of the used nuclear fuel assemblies is at least as much a political and societal problem as an actual technical problem. A typical 1 gigawatt nuclear reactor of current pressurised water technology generates about 7 billion kWh per year, enough to power the city of San Francisco. Every year this nuclear reactor generates 35 used fuel assemblies containing about 1 tonne of highly radioactive elements together with about 17 tonnes of unused uranium. The volume occupied by these 35 fuel assemblies is about 6.2 cubic meters.

Assuming a typical consumption of 7,000 kWh per year, a person living in San Francisco would be responsible for the production of about 6.2 cubic centimeters of used nuclear fuel per year weighing 18 grams if the electricity came only from a nuclear power plant. It would take about 55 years for this person to fill the equivalent of a can of soda with used nuclear fuel. So, yes, these used fuel assemblies contain very dangerous materials—standing next to one, unprotected, would kill you in a few minutes—but there is very little of it. If the same electricity had come only from a gas—natural or bio—power plant during the same 55 years, that person would have been responsible for the emission of about 190 tonnes of CO2—900,000 cans of soda or one every half-hour—and twice that amount if it had come from a coal power plant.

Can we cut CO2 emissions without nuclear?

It will be possible if the deployment of environmentally friendly, cost effective, gigawatt-scale energy storage systems and/or billion-tons-per-year carbon capture and storage prove practical. It will not be possible if neither of those prove feasible in the next 30 years. The World Energy Council considers these two technologies as the key uncertainties in moving toward a low-carbon economy up to 2050. Without grid-scale energy storage, energy plans involving large wind and solar penetrations contain a significant part of wishful thinking. In the meantime, it would make a lot of sense to expand the use of nuclear power in the energy mix. Unlike the other two options mentioned above, expanding the use of nuclear power does not really require any technical breakthroughs. Nuclear power is not a panacea but, everything considered, and emotions aside, experience shows that it does not entail more risk than other industries.

NOTE: Gilles Youinou, PhD, is the head of the Reactor Physics Design & Analysis department at Idaho National Laboratory. Youinou is currently involved in nuclear and thermal-hydraulics design activities in support of the U.S. Department of Energy’s Versatile Test Reactor (VTR) programme. Views expressed represent those of the author and do not necessarily reflect those of INL or DOE.​ The article was first published on rdmag.com.