As media reports of workers heroically trying to head off multiple meltdowns in the smoking bowels of the stricken Fukushima Daiichi-I nuclear power plant played over scenes of thousands of evacuees fleeing radiation after Japan's powerful earthquake and tsunami, the global nuclear power industry was facing its own public relations meltdown.

Governments around the world are pushing the nuclear pause button: shutting plants for safety checks and reevaluating energy policy. Even staunch nuclear advocates on Capitol Hill are calling for a timeout on new US nuclear plants in order to learn lessons from Japan's tragedy. And American public support for nuclear development slid a precipitous 10 points – from 57 percent a week before the March 11 quake to 47 percent the week after.

Yet in spite of it all, nuclear industry observers say, Fukushima is unlikely to kill development of nuclear power in a world desperate for a clean – and unlimited – alternative to fossil fuel energy.

"[The Fukushima disaster] is going to slow things down, but not stop them," says Charles Forsberg, head of the nuclear fuel cycle project at the Massachusetts Institute of Technology, in Cambridge, Mass. That, he says, is because there are few alternatives to provide the electricity the world needs.

The Japanese disaster, say experts, probably will slow deployment of new plants by increasing safety regulations, heightening public opposition, and vastly increasing the cost of capital to finance hugely expensive construction.

But, says Spencer Weart, former director of the history center at the American Institute of Physics and author of two books on nuclear power's emergence, "What history suggests is that, unless this crisis causes very widespread damage, the Japanese government, even now, may ultimately feel it has no choice but to go ahead with nuclear power.... [E]ven after Chernobyl, the Russian government went ahead to develop nuclear energy because they feel that when oil runs out they're going to need it."

Indeed, while nuclear energy provides 14 percent of the world's electricity, according to the World Nuclear Association, many nations heavily depend on it: France gets 75 percent of its power from nuclear technology; Japan, 30 percent; and the United States, 20 percent. And nuclear energy figures dramatically in China's soaring economy: It has 13 operating nuclear power plants and 27 under construction, according to the International Atomic Energy Agency (IAEA).

Ever since the atomic age dawned with the bombing of Hiroshima, nuclear technology has been fraught with promise and peril.

Nuclear power's big allure has always been the idea of cheap, limitless power – "electricity too cheap to meter," as one 1960s era slogan termed it. By the mid-1980s, however, nuclear plant construction cost overruns, nuclear utility bankruptcies, and the frightening, costly accidents at Three Mile Island in Pennsylvania and Chernobyl in Ukraine had soured public opinion on nuclear power.

But in the past decade, the idea of a "nuclear renaissance" had bloomed as a clean, alternative to fossil fuels that might be an antidote to global warming.

And Americans supported the renaissance: After 25 years without a major accident, Gallup found 62 percent support for nuclear energy last March – the highest since the polling firm first asked the question in 1994.

Before Fukushima, more than 60 nuclear reactors were under construction in 15 countries – including, at the head of the pack, China, Russia, and South Korea. Other nations like Jordan, Saudi Arabia, Thailand, and the Philippines were lining up for their first nuclear plant.

Even respected environmentalists such as Whole Earth Catalog founder Stewart Brand and Greenpeace cofounder Patrick Moore had joined the "renaissance" as a last ditch effort to head off climate change.

"My views have changed, and the rest of the environmental movement needs to update its views," wrote Mr. Moore in 2006. "Nuclear energy may just be the energy source that can save our planet from another possible disaster: catastrophic climate change."

But as an exploding, burning nuclear plant in Fukushima spewed radioactive smoke on surrounding cities earlier this month, Mr. Moore was horrified. "I was quite upset by what I saw."admits the former antinuclear activist now employed by the Nuclear Energy Institute trade group.

Illustrating the pragmatism that experts say is likely to prevail over the long term, Moore still supports nuclear power: "I have not in any way lost my support for nuclear energy. What's happening is such a unique event, a tragedy.... Until a thing like this is over, you don't know what the consequences will be. I'm just hopeful if they do rebuild on sites like this in Japan that they will make sure it can withstand this type of tsunami.... I'm sure we will all learn from this."

He suggests the accident was due to freak coincidence: Emergency shut-off systems had actually worked and cooling systems would have, too, if the massive quake had not been so quickly followed by a tsunami that knocked out backup generators.

Though the Environmental Defense Fund (EDF) doesn't explicitly endorse it, the group has adopted a "moderate" stance on nuclear power and echoes Moore.

"We understand nuclear provides 20 percent of our electricity," says Elgie Holstein, EDF director of strategic planning. "We're not calling for a wholesale shutdown of the American nuclear fleet in light of what's transpired in Japan. But we join other groups in saying we need to follow a very careful set of steps, to reassure ourselves that the regulation of nuclear power, our plants operations, are up to the best safety standards."

Yet, the Union of Concerned Scientists (UCS), which is sharply critical of nuclear safety in the industry, looks to the Fukushima accident for lessons, since there are 23 plants with the same or very similar General Electric Mark 1 Boiling Water Reactor designs spread across the US.

Existing nuclear plants like California's Diablo Canyon and San Onofre, and others in active seismic zones prone to earthquakes will probably have to undergo significant review to ensure safety, according to the UCS. Even in less active seismic areas, recent analysis shows "slight increases to earthquake hazard estimates for some plants in the central and eastern US," according to a November Nuclear Regulatory Commission fact sheet. New nuclear plants are a much bigger question.

Just how fast nations plow ahead on nuclear – or back away – will vary by nation depending on its energy resources and its political systems, says Dr. Weart.

President Obama was quick to say that Japan's experience would not prevent the US from building new nuclear plants. Others echoed that. But even diehard nuclear supporters are pulling back at least a bit.

"I think it calls on us here in the US, naturally, not to stop building nuclear power plants but to put the brakes on right now until we understand the ramifications of what's happened in Japan," Sen. Joseph Lieberman (I) of Connecticut said on CBS's 'Face the Nation.' "

Fukushima has set off a flurry of review in Europe, for example. European Union member states decided to conduct stress tests for the impact of tsunamis, earthquakes, terrorist attacks, and loss of power on 143 nuclear plants. Switzerland will not renew operating permits for three of that nation's five nuclear plants.

Most dramatic, German Chancellor Angela Merkel – who last fall reversed the nation's phase-out of nuclear power – announced another "turnaround": The country will now create a timetable for an exit from nuclear power; and it shut seven of its oldest nuclear plants for a three-month safety review, with the possibility of closing them permanently.

In Asia, China is suspending approvals for new nuclear power plants so it can conduct safety checks on existing plants and those under construction. And Thailand will reevaluate whether to build its first new nuclear plant.

President Hugo Chávez said Venezuela would not pursue earlier plans for a nuclear station.

On the other hand, Sweden, with 10 reactors, reiterated its conviction not to scrap its reactors. And in Indonesia, where four reactors are planned not far from active faults, officials said the plans would proceed.

In France, with one of the world's most ambitious nuclear programs, parliamentary leaders demanded a study on "the future of the French nuclear industry."

But, says Dr. Weart, "France and Japan have no oil and not much coal. They are going to go ahead because they have to."

Indeed, France and Japan are heavily reliant on nuclear power because of strategic energy decisions caused by conflicts over oil, says Dr. Forsberg, of MIT. A major reason the Japanese attacked Pearl Harbor, he says, was to protect the supply of oil in Asia. France, similarly, warred with its colony Algeria in the 1950s and 1960s mainly to protect access to oil and gas in North Africa.

"People don't appreciate that some of [other countries' commitment to nuclear power] is based on major historical factors," he says.

Meanwhile, notes Weart, nations such as China "have centralized governments that tend to be able to go ahead without too many legal or regulatory impediments and without much concern for public opinion."

Perhaps the biggest hurdles to new nuclear power generation will not come from politicians, regulators, or a frightened public. Wall Street has refused to underwrite loans for any nuclear plant unless it has 100 percent of the loan guaranteed by the federal government. The Fukushima disaster means that the cost of borrowing money for such plants will be even higher, raising the question: Will nuclear power plants – at $10 billion per reactor – be too expensive to build?

Some observers are adamant that it will be prohibitive in the US, arguing that low natural gas costs that make gas turbines a cheap option, excess generating capacity, and very low growth in electricity demand will make nuclear too costly.

"Some in Congress talk about doubling or tripling the size of the existing nuclear fleet to face our energy challenges," Jon Rowe, president of Exelon, one of the nation's biggest utilities which owns several nuclear plants, said in a speech this month.

"Since these plants are not currently economic at today's low natural gas prices, the government would have to spend $300 to 600 billion to get these plants built," he says. "Congress should not expand the nuclear loan guarantee program beyond the current $18.5 billion already allocated" or extend tax credits.

Not exactly a ringing endorsement from one of the most likely buyers of a new nuclear plant. Others point to poor economic conditions and weakening public support as major hurdles to new plant construction.

"What this means is that the notion that we were about to launch a new era of nuclear plant construction will probably have to be reexamined," says Mr. Holstein, senior strategic director for the EDF. "That's not to say there isn't a future for nuclear in the United States. But their job just got a lot tougher."