Save the polar bear? Go nuclear.

That is one way to beat climate change, or so says the Nuclear Energy Institute. When the industry group posted on its Web site poll results reflecting shifting opinions about nuclear power, it tossed in a picture of a polar bear traipsing across the tundra.

But industry opponents see a more threatening beast in their midst, like a hungry grizzly emerging from the woods after decades of hibernation.

The nuclear question is back. And this time the environmental front is divided — a victim of its own success in sounding alarms about global warming.

Even in Pennsylvania, home to the Three Mile Island fright of 1979, the Democrats competing in Tuesday’s presidential primary have signaled a willingness to consider nuclear power as an alternative to carbon-coughing electric plants fueled by coal.

Few voters have even pressed them on it.

“A whole generation has grown up here knowing nothing about Three Mile Island,” said Judith Johnsrud, an adviser to the Pennsylvania Sierra Club. The plant’s partial meltdown put proposals for new U.S. nuclear reactors on ice for a quarter-century.

Sen. Hillary Clinton of New York, who calls herself “agnostic,” or uncommitted, on the issue, blends urgent warnings about shipping and storing radioactive waste with pledges to put the nuclear option on the table.

“We do have to look at it because it doesn’t put greenhouse gases into the air,” she has said.

Similar remarks come from Sen. Barack Obama of Illinois, which has the most nuclear reactors of any state. Both candidates have received donations from nuclear companies’ employees.

The office of Gov. Kathleen Sebelius, also a Democrat, recently outlined her views on national energy policy in the wake of rejecting a coal-fired plant’s expansion in western Kansas:

She “recognizes that diversifying our energy portfolio is important … and all options should be considered, including nuclear power.”

President Bush on Wednesday announced a goal of stopping the growth of U.S. greenhouse-gas emissions by 2025. The presumptive Republican presidential nominee, Sen. John McCain of Arizona, has proposed billions of dollars worth of tax breaks and federally-backed loans for nuclear development.

Mood has changed

The nuclear industry, which produces most of France’s electricity, faces many unresolved obstacles to its growth in the United States.

Wary insurers and enormous construction costs — roughly $8 billion per reactor — demand federal aid and loan guarantees.

Plans to store waste at Nevada’s Yucca Mountain Repository remain in legal and political limbo. The Energy Department was slated to begin accepting spent fuel there a decade ago.

Still, eight power companies have applied for federal licenses for new reactors. About two dozen sites have been pitched for new nuclear facilities. Currently, 104 reactors provide about 20 percent of the nation’s electricity.

“What’s held us up in the past,” said Derrick Freeman, who directs legislative efforts for the Nuclear Energy Institute, “is that America took on a sour mood about nuclear power after Three Mile Island and the Chernobyl disaster” in the Soviet Union in 1986. The Chernobyl blast directly caused at least 50 deaths, and some areas around the plant remain off-limits.

“That (mood) has changed,” Freeman said.

A few years ago the group Environmental Defense reconsidered its opposition to nuclear energy and now considers it a “low-carbon option.”