In an ironic twist, concern over the environment -- global waming and greenhouse gas emissions -- may help revive the long dormant nuclear power industry in the United States. For the first time since 1978, applications for new licenses to build new plants are being submitted. Moreover, the U.S. Nuclear Regulatory Commission has already extended the licenses of roughly half the 104 nuclear plants already on line, which produce about 20 percent of the nation's electricity. 

AmerenUE, the owner of Missouri's only nuclear plant, is pursuing a license to construct a new nuclear plant adjacent to the Callaway plant, which was completed in 1984 and produces about 13 percent of Missouri's electricity. (The utility won't decide whether to build the plant for another two years.)

As nuclear power seems to be enjoying a resurgence, have the environmental questions that derailed it in the '80s been resolved? Is nuclear power safe? Is there a solution for the radioactive waste?

How many ways can you boil water?

Today, no matter the type of power plant, almost all electricity is made by heating water to make steam and using that steam to spin a generator's turbine. Most power plants burn coal or natural gas to boil water, releasing tons of carbon dioxide from the combustion process. Nuclear power plants, however, heat the water using fission reactions, splitting atoms of uranium or plutonium and producing no carbon emissions. Proponents of nuclear power say it's the only way to produce low-carbon electricity on an industrial scale.

Take the entire energy cycle of a nuclear plant into consideration, however, and the low carbon picture is not so clear. Uranium must be mined and refined from the ore that comes out of the ground, an energy-intensive process. The refined uranium must be transported to the nuclear power plant, which must first be built. Construction of new nuclear power plants is a notoriously long and expensive undertaking. It requires energy-intensive building materials like concrete and fuel-burning construction equipment, all of which release carbon.

Once the relatively clean-running nuclear plant is online, it produces radioactive waste in the form of spent fuel rods. This waste must be reprocessed into another usable radioactive product and stored under strong security or transported as waste and stored under strong security, all while being kept cool. Eventually, the plant must be decommissioned, a process with which even the experts have little experience, as most nuclear reactors built in this country are still in operation.

Proponents of nuclear power point out that the construction of any power plant -- whether fueled by coal or natural gas -- produces a lot of carbon. And some kind of electricity-producing plants must be built to meet the world's growing demand for energy. The difference, according to the pro-nuclear argument, is that the process of electricity production in nuclear plants releases no carbon dioxide. In addition, a relatively small amount of uranium can produce a relatively large amount of energy, helping the overall energy cycle of an online nuclear plant to release no more carbon dioxide per kilowatt-hour than solar power, which must account for the manufacturing of photovoltaic cells.

It's a classic dilemma: If the solution to the climate problem is to reduce carbon dioxide emissions through nuclear power, then future generations spared catastrophic global warming must figure out what to do with our radioactive waste.

Nukes are safe, unless they're not

The United States, France and Japan are the world's leading producers of nuclear energy. In fact, nuclear power plants in France and Japan produce the majority of these countries' electricity because they lack fossil fuels. Proponents of nuclear power point out that these countries have been using nuclear power for decades and that it has, in large part, been safe.

The major accidents at Three Mile Island in Pennsylvania and Chernobyl in the then-Soviet Union show that human error is the biggest risk in the operation of nuclear plants. Chernobyl, the largest civilian reactor disaster in history, killed 56 people and made the surrounding land uninhabitable. Proponents of nuclear power note that no one died as a direct result of the Three Mile Island accident and the radiation was contained. New reactor designs, especially in France, have improved safety further, with multiple backup cooling systems.

Other than the catastrophic scenario of widespread radiation release that kills people and renders large areas uninhabitable, one of nuclear power's most obvious environmental and safety problems stems from the periodic release of radiation. With the small amounts of radiation that get out comes the question of exposure. Conflicting studies provide few answers about "safe" levels of radiation versus levels that cause cancer. Japan is dealing with this question as it inspects its nuclear power facilities following the 7.2 magnitude earthquake that struck June 14, 2008. There was no widespread nuclear disaster, but the Tokyo Electric Power Co. admitted that a radioactive water leak occurred at one plant, but claimed it posed no threat.

Besides nuclear meltdown and radiation leaks, a third major danger from nuclear power comes from radioactive waste. For now, nuclear waste is stored in pools at the site and is a risk for contaminating the environment, including ground water. High-level waste must be kept cool, using water. Time is an issue as well because the waste remains radioactive for thousands of years. Pro-nuclear groups argue that the waste problem can be safely managed with fuel reprocessing and by burying it underground. There, far from the surface, it can decay, becoming less radioactive over time. The first step is to agree on where to put it. Today, nuclear waste has no permanent storage facility.

Beyond climate

Carbon-dioxide emissions and radioactive waste are not the only environmental issues.  A massive component of nuclear power generation is the water used for steam production and for cooling the nuclear fuel. Nuclear power plants are always near water and the neighboring river, lake or ocean sees its local temperatures rise because of the warm water returned from the power plant, threatening the local ecosystems.

Still, nuclear power does not produce the dirty emissions of coal-fired power plants, including soot, mercury and sulfur dioxide. Boosting the pro-nuclear argument, a 2004 study by the Natural Resources Defense Council found that the contaminants released from coal-fired power plants led to some 24,000 premature deaths in the U.S. a year.

No method to mass produce electricity may be entirely safe; any decisions must balance risk, cost and benefit. At this point, though, it's still an open question whether Missouri further pursues the nuclear option. 

Julia Evangelou Strait is a freelance science writer based in St. Louis. She has a master's degree in biomedical engineering and works in hospital epidemiology for BJC HealthCare.