Simpler - and safer

It's a simple proposition: Make electricity by boiling water and letting the steam drive turbines to crank the generators. But when the heat needed to boil water comes from splitting atoms, the technology is anything but simple.

Now, in its bid to make a comeback in the United States a generation after the Three Mile Island accident, the nuclear-power industry is addressing two of its major bugaboos - safety and cost - through technology. Its answer: a new generation of reactors that are simpler to operate and maintain than today's models.

The move is already under way.

Over the past two months, one major US utility and a separate consortium of utilities have signed agreements with the US Department of Energy (DOE) to split the cost of testing a streamlined federal program for licensing the construction and operation of new nuclear plants. The goal is to begin installing these new reactors by 2010.

Over the longer term, 11 nations including the US are working on so-called fourth-generation reactor designs that proponents say have the potential to be safer, cheaper, and more reliable than older models. At one end of the size scale, some alternative designs aim to produce electricity for major utilities along with the hydrogen needed for President Bush's "hydrogen economy." At the other end of the scale, some designs are being tailored to power and heat small rural communities. Last December, for example, the tiny Alaskan town of Galena accepted an offer from Toshiba to build and install a small reactor some have dubbed a nuclear "battery." It would supply the town with electricity and heat. The town now is in the early stages of seeking approval from the US Nuclear Regulatory Commission to install the reactor.

The twin drivers behind these efforts are projections of increasing demand for electricity and rising concerns about greenhouse gases - something that nuclear power doesn't produce.

In the US alone, utilities will need to build 281 gigawatts of new generating capacity by 2025 as demand rises and older coal- and oil-fired plants are closed, the DOE estimates.

Climate scientists trace warming temperatures largely to greenhouse gases added to the atmosphere from burning fossil fuels such as coal, oil, or natural gas. The nuclear industry has long argued that nuclear energy must remain an option to reduce those emissions. But it's been a tough sell. Accidents at Three Mile Island in Pennsylvania in 1979 and Chernobyl in the Ukraine in 1986 still echo in public discussions. These memories are kept fresh by many environmental groups who see nuclear energy as too dangerous and too expensive. They push instead for greater energy efficiency and increased reliance on renewable energy sources.

Yet faced with global warming, some groups, such as the Pew Center on Global Climate Change and Environmental Defense, appear willing to give nuclear energy a reluctant second look.

Support for new reactors also appears in a bill introduced last Thursday in Congress. Sens. Joseph Lieberman (D) of Connecticut and John McCain (R) of Arizona offered the Climate Stewardship and Innovation Act of 2005. It would require the Environmental Protection Agency to set limits on emissions of greenhouse gases and set targets for achieving them. The duo has introduced similar bills in the past. But the latest measure outlines a mechanism to fund the development of new technologies to help achieve those targets. Among those technologies: three unspecified new nuclear-reactor designs.

"Nuclear has a lot of problems, and only if it can solve its problems should it be part of the mix," says Judith Greenwald, director of innovative solutions for the Pew Center. The list she cites includes cost, public concerns over safety, nuclear-waste disposal, and nuclear proliferation.

But, she adds, the industry's emerging reactor designs appear to address some issues. In addition, the industry "seems to be coalescing around a small number of standard designs," compared with its current collection of 104 essentially custom reactors. Such standardization could make it cheaper to build them and easier to train people to operate them.

The latest designs likely to hit the grid come from US manufacturers Westinghouse and General Electric, as well as foreign companies such as Areva in France.

These designs make extensive use of natural processes, such as convection and gravity, in their emergency cooling systems instead of the mammoth pumps and series of valves found in older reactors, which are prone to failure or operator error, says Per Peterson, who chairs the nuclear engineering department at the University of California at Berkeley. Only a small number of battery-operated valves need to open for the emergency cooling systems to kick in. The combination not only reduces the amount of internal plumbing at the plant, he says, it also reduces the need for diesel generators that keep the cooling system operating in case the plant is shut down for maintenance or an emergency.

Overall, "the new, simplified designs eliminate an enormous amount of equipment inside the reactor building," he says. That reduction leads to plants that are much cheaper to build and maintain, he adds. These designs first emerged about four years ago as "third-generation" designs. They have evolved into what many are calling third-generation-plus designs.

In January, the US signed a cooperative agreement with Japan, Canada, France, and Britain to begin development of fourth-generation designs that use a variety of exotic materials - liquid sodium, molten salt, lead, or helium gas - as coolants. Fuel for some of these designs comes in the form of assemblies filled with coated uranium pellets, each about half a millimeter across. Coatings would be designed to withstand high temperatures in case a reactor loses coolant, thus providing a first line of defense against leaks.

As part of this effort, the US is working on a high-temperature reactor using a helium coolant, says Kathryn McCarthy at the Idaho National Laboratory near Idaho Falls. The reactor would use the pellet-like fuel and materials that turn the laws of physics into an automatic shutdown mechanism if the reactor loses its coolant.

The design, which aims to sustain sufficiently high temperatures to produce hydrogen as well, will push the envelope on new materials that can withstand the harsh environment, she acknowledges. From the range of reactor concepts being examined by the international group, which also includes Argentina, Brazil, the European Union, South Africa, South Korea, and Switzerland, the DOE hopes to narrow the choices by 2012, then settle on one or two standard designs.

Many remain skeptical that new reactors will solve many of nuclear energy's current conundrums. For one thing, many of these designs could be run as breeder reactors, generating plutonium as a byproduct and thus raising nuclear-weapons proliferation concerns.

Moreover, reliance on passive systems could undermine the multilayer, defense-in-depth approach to radiation containment, says Edwin Lyman, a scientist with the Union of Concerned Scientists. "We're still learning about how stainless steel degrades" in current reactors.

In 2002, workers at the Davis-Besse plant in Ohio discovered a football-size hole in the top of the steel housing containing the reactor. The corrosion was traced to dry boric acid that had collected atop the reactor vessel. A study later conducted by the Oak Ridge National Laboratory concluded that had the condition - overlooked for six years - gone unnoticed much longer, the hole would have opened wide enough to trigger a loss of coolant worse than Three Mile Island.