With the Obama administration staking the nation's energy future on clean sources, the U.S. nuclear power industry aims to make a comeback by building dozens of new reactors that supply plentiful, carbon-free electricity.

But 30 years after the Three Mile Island accident in Pennsylvania led to moratoriums on new plants across the nation, concerns about the cost and safety of nuclear power remain, including what to do with the growing stockpiles of highly radioactive waste from the nation's reactors.

President Obama's campaign pledge to find an alternative to burying the deadly waste at Yucca Mountain, Nev. - and recent votes in Congress to slash funding for the proposed nuclear graveyard 1,000 feet underground - could hobble the industry's hopes of providing a larger share of U.S. energy needs.

Still, industry leaders voice confidence about nuclear power as a clean source of electrical energy that can reduce the nation's reliance on dirty, coal-fired power plants that emit greenhouse gases, cause acid rain and speed climate change.

Applications to build at least 31 nuclear reactors are before the U.S. Nuclear Regulatory Commission, with more filings expected soon. Many of the projects are in the Southeast, with the first expected to go on line as early as 2015. Nuclear advocates hope eventually to build additional reactors in California.

"I'm aware of 33 or 34 projects in the hopper. I think the prospects are reasonably good. There's demand," said Bill Halsey, a leading expert on nuclear energy at the Lawrence Livermore National Laboratory, where scientists have worked on solutions for permanent disposal of high-level radioactive waste.

New reactors

Nuclear power supporters predict that approval of pending construction licenses for new reactors in Florida, Alabama and Texas will raise demand for nuclear power in California, which has banned new reactors since the late 1970s because of concerns over waste disposal.

Obama has emphasized alternative energy sources such as wind and solar power, but also pledged to re-examine nuclear energy.

Officials at the Livermore lab hope to use a fresh infusion of federal funds to refine methods of disposing of or recycling nuclear reactors' spent fuel, which can remain highly toxic for hundreds of thousands of years.

The lab is run by a consortium headed by San Francisco's Bechtel Corp., which also builds nuclear power plants overseas.

Nuclear power opponents include the Sierra Club, the nation's oldest environmental group.

"Our view is that the nuclear industry has yet to demonstrate that they know what to do with the waste they generate," said Carl Pope, the club's executive director, "and they have yet to demonstrate that they can build and operate new reactors with their own money. They have yet to meet the test of the market. So we think it's a very poor investment of public money."

Meanwhile, global warming has prompted some conservationists, such as Greenpeace co-founder Patrick Moore, to conclude that nuclear power will be a crucial energy source in the future.

'Not-so-good options'

"Many people are gritting their teeth and beginning to look at nuclear energy because the problems appear to be more manageable," said Per Peterson, a professor of nuclear engineering at UC Berkeley. "Nuclear energy is the only source that we've found that can directly displace coal for reliable, full-time electrical generation. ... It's the best of a set of not-so-good options."

There are about 440 nuclear power plants operating worldwide, including 104 commercial reactors in the United States. Four reactors are in California - two at Diablo Canyon near San Luis Obispo and two at San Onofre in Southern California. Energy from those plants, plus nuclear power imported from Arizona, accounts for 15 percent of California's electricity supply.

Nuclear reactors supply nearly 20 percent of U.S. electrical energy, and industry advocates say nuclear energy provides about three-quarters of the nation's carbon-free electricity. They also say reactor safety has improved significantly since Three Mile Island's meltdown in 1979.

Under California law, no new nuclear power plants can be built in the state until the industry finds a way to permanently dispose of its waste. Spent fuel rods are currently stored on site at U.S. nuclear plants.

Meanwhile, other nations, including China, are building nuclear reactors at a rapid rate. France, Britain and Japan rely heavily on nuclear power.

Building a reactor costs several billion dollars, which utilities and owner/operators hope to fund through bank loans, rate increases and federal loan guarantees.

In 1987, Congress chose Yucca Mountain as the nation's future repository for spent fuel rods from nuclear reactors. The state of Nevada has opposed the project.

"Over the last 40 years, a very broad scientific consensus has emerged that nuclear waste can be managed safely by a combination of recycle and deep geologic disposal," UC Berkeley's Peterson said. "There's political controversy, but the technical consensus is that the level of isolation will be sufficient to protect long-term public health and the environment."

The Department of Energy has applied to the Nuclear Regulatory Commission to build the repository at Yucca Mountain, but funding for the project has been severely cut.

Nuclear waste fee

A recent study by the Congressional Research Service says that it would cost about $100 billion to dispose of the waste from U.S. nuclear reactors and dismantled weapons at the site. But nuclear advocates say these costs are nominal.

"The nuclear waste fee is only about a percent of the value of energy taken out," said Jim Blink, a scientist at Lawrence Livermore National Laboratory. "Nuclear has such a small amount of waste per unit of energy that we can afford to collect it and dispose of it in a way that's isolated from the biosphere."

Blink and other scientists spent two decades evaluating the suitability of Yucca Mountain as a permanent graveyard for nuclear waste, which currently includes about 60,000 metric tons from civilian reactors plus additional tonnage from the military.

They have done extensive studies of volcanic rock there, built a corrosion testing lab to simulate underground conditions, designed corrosion-resistant dry casks to hold spent fuel rods and used supercomputers to calculate the risks of permanent disposal.

Meanwhile, researchers and engineers are developing the next generation of nuclear reactors that will be capable of recycling spent nuclear fuel, leaving a residue of material whose high-level radioactivity is of shorter duration. Those reactors are not expected to go on line for 20 to 30 years.