If carbon emissions from energy production are the problem, is nuclear power the solution? After all, nuclear reactors split uranium atoms to generate heat; no fossil fuels are used on site, and no CO2 is released into the air from the power plant itself. Plenty of voices can be now heard advocating construction of nuclear plants in order to save the environment. The Obama administration supports new loans and incentives for nuclear power, as does the Kerry-Lieberman climate and energy bill.
It's not quite that simple. The nuclear power life cycle includes many steps, from mining and enriching uranium, building the reactor, operating the plant, processing and disposing of the spent fuel, through, someday, decommissioning the plant when it can no longer be used. Many of these stages are quite energy-intensive, so there are life-cycle greenhouse gas emissions from nuclear power. The best available data show the life-cycle emissions from nuclear power to be much lower than from fossil fuel-burning power plants, but equal to or higher than the emissions from renewable energy, such as solar, wind, and hydro-power.
A comprehensive literature review by Sovacool (2008) screened the available studies on greenhouse gas emissions from nuclear power, identifying 19 studies that met several criteria for reliability. The same literature review reported estimates of life-cycle emissions from renewable electricity generation ranging from 9 to 41 mT CO2-e per MWh, with wind and hydropower at 9 to10, and photovoltaics at 32. Fossil fuel-burning plants, in contrast, ranged from about 440 mT CO2-e per MWh for natural gas combined cycle turbines, up to 1,050 for some coal plants. Thus nuclear power has much lower life-cycle greenhouse gas emissions than fossil fuels, but higher than leading renewable technologies.
There are a number of uncertainties in estimating emissions from the nuclear fuel cycle. The quality of uranium ore makes a big difference; mining and processing ore with lower concentrations of uranium uses more energy per MWh of electricity. The choice of enrichment technology is also important; much of the world uses gas centrifuges, which require much less energy than the gas diffusion technology used in the United States. Finally, the end of the nuclear life cycle, encompassing the disposal of spent fuel and other radioactive waste, along with decommissioning of retired reactors (parts of which are by then radioactive), remains a subject of guesswork, with the siting, design, and construction of a final waste repository still an unsolved problem.
With all this in mind, how does nuclear power measure up to the alternatives? On grounds of greenhouse gas emissions alone, nuclear power looks like a big improvement over fossil fuels, with about 15 percent of the emissions (per MWh) of efficient natural gas-burning plants. On the other hand, wind and hydro-power have about 15 percent of the emissions of nuclear plants; photovoltaics may have half the emissions of nuclear power.
Meanwhile, there are a host of other questions about nuclear power, which would have to be answered if it were to become a bigger part of our energy system. The safety concerns, from the era of the Three Mile Island and Chernobyl accidents, may be the least of the current problems; improvements in U.S. reactor operations have led to fewer outages and more reliable performance in recent years. Reactors remain staggeringly complex systems, in which the myriad possible pathways to failure cannot all be anticipated and planned for in advance, but for now, they appear to be under control. New reactor designs may allow for safer operations in future plants.
Safety, however, is not cheap; the price of making a reactor reasonably safe drove construction costs far up into the billions of dollars, bankrupting some of the original investors and raising the price of electricity from nuclear plants. It is vitally important to avoid the temptation to make nuclear power more affordable by cutting corners on safety — as the recent Deepwater Horizon oil rig explosion in the Gulf of Mexico has amply demonstrated, expensive environmental and safety regulations are adopted for very good reasons.
Nuclear power plants are also thirsty: Huge volumes of cooling water are required to keep temperatures under control. Heat waves and droughts have forced cutbacks in nuclear power production, in both the United States and Europe, in recent years. All thermal power plants, whether fossil fuel-burning or nuclear, require cooling water, but nuclear power requires the most of all. According to a U.S. Department of Energy study, nuclear plants with closed-loop cooling (recycling water within the plant instead of using it once and then returning it to its source) consume 720 gallons of water per MWh of net power produced; the comparable figures are 310 to 520 gallons per MWh for several types of coal plants, and 190 gallons per MWh for natural gas combined-cycle plants.
Investing in a technology that needs a lot of cooling water seems less than ideal in a world in which climate change is making many areas hotter and drier. The hottest days of the summer are the times of peak electricity demand, when every air conditioner is turned on — not a time when major power plants should be going off-line.
Finally, the nuclear waste problem won't go away. The federal government has promised to build a permanent disposal site, but has failed to do so; as a result, ever-growing numbers of spent fuel rods are being stored in ponds near nuclear reactors around the country. Some of the wastes produced by nuclear power will be dangerous for thousands, if not tens of thousands, of years — an environmental hazard that is even longer-lived than the climate crisis. Until this problem is solved, and the cost of the solution is known, nuclear power can't be a dependable answer to our energy needs today.