When Reactor No. 4 at the Chornobyl nuclear power plant exploded 25 years ago, it seemed nuclear power might die with it.
Around the world, people recoiled in horror as radioactivity from Ukraine spread with the wind. As it settled hundreds and even thousands of kilometers away, scientists monitored the concentrations to see if the areas would become too dangerous to inhabit.
Even today, the health concerns continue in unexpected ways. Britain still restricts the sale of meat from sheep that graze in certain parts of Wales. And Germany bans the sale of meat from boars in the south of the country, as well as the mushrooms they consume.
But if the Chornobyl accident in 1986 shook public confidence in nuclear power, it did not spell its end.
In the following years, the global rate of new power-plant construction slowed. But nuclear plants still kept on providing about 16 percent of the world's growing demand for electricity. A Nuclear Renaissance
The nuclear industry did so by upping the output of existing plants to largely avoid building new ones in the face of public hostility. According to the International Atomic Energy Agency (IAEA), just one-third of the additional electricity generated by nuclear power over the past two decades was from new plants.
A child's gas mask and shoe at a kindergarten in the abandoned city of Prypiat near Chornobyl
But by 2001, as memories of Chornobyl faded, the climate for nuclear power became favorable again. Rising fossil fuel prices and concerns over global warming prompted talk of a "nuclear renaissance."
As of this year, the IAEA reports that there are 64 new plants under construction in addition to the 443 plants older plants already operating worldwide.
Even the United States joined the turn-around. In 2010, Washington promised to guarantee more than $8 billion in loans to help build the first new U.S. nuclear plant since the Three Mile Island disaster in 1979.Fukushima Reawakens Old Doubts
Now, as Japan's Fukushima Daiichi reactors produce the worst radiation leaks since Chornobyl, doubts about nuclear power are suddenly back with a vengeance.
Japanese protestor, Mayoko Nakahara, expressed the feelings of many in Japan at an anti-nuclear demonstration in Tokyo last week when she said that the time had come for her country to "get rid of nuclear energy."
"I've had worries about [Japan's] nuclear policies for some time, and if we don't take advantage of this opportunity who knows when the [antinuclear] movement will have this much energy again," she said. Different Approaches In Different Countries
Rising safety fears have prompted several nations, including China, to freeze plans for new reactors pending reviews. In Germany, which has one of the world's strongest anti-nuclear movements, the government has shut seven of the country's oldest reactors for three months.
But are the Fukushima accident and the reawakened memories of Chornobyl strong enough to put the future of nuclear power in doubt once more?
After the Fukushima accident, many countries have frozen plans for new nuclear plants, pending reviews.
James Acton, a nuclear expert at the Carnegie Endowment for International Peace in Washington, D.C., believes the answer will likely vary from country to country.
"Where public opinion matters, then I think that on average Fukushima is likely to have a negative effect on the growth of nuclear power," he says.Risks Versus Economic Advantages
Those countries where public opinion matters most correspond closely to the list of countries which currently have most of the world's reactors. In descending order, the countries with the largest number of nuclear power plants are the United States with 104, France with 58, and Japan with 54.
However, among those countries there are widely varying assessments of the risks of nuclear power compared to its economic advantages.
The United States, despite its interest in building a new generation of safe reactors, is becoming increasingly interested in shale gas as an alternative fuel instead.
By contrast, France is resolutely pro-nuclear and is likely to remain so.
And Japan -- in the midst of the Fukushima crisis -- will likely have to go through a prolonged national debate before its future course becomes clear.
But Acton predicts that where public opinion doesn't play a major role in forming government policymaking, nuclear power will continue to expand. Among those countries is Russia, whose 32 current nuclear power plants put it in fourth place in the world ranking.
Vitaly Fedchenko, a researcher at the Stockholm International Peace Research Institute in Sweden, says Moscow appears fully committed to going ahead with the nuclear energy program it adopted a few years previously.
The IAEA says 39 of the 64 nuclear power plants currently under construction are located in Asia.
"I think the target was [that] 25 percent of electricity production should be nuclear [and that] still stands, at least officially," he says.
"Now, there are questions about how to get there; there are technical issues with production of reactors simply in terms of capacity, but as far as I know on the political level that decision is there and I am not really aware of serious debate about that."
For Moscow, nuclear technology is not only seen as an integral part of the domestic economy but also as a valuable export product.
Russia competes strongly with other nuclear-technology exporters like France, the United States, and Canada for contracts worldwide.
"As far as exporting is concerned…it is seen as a good thing because in Russia there is this discussion about trying to export more hi-tech products as opposed to crude oil and that kind of thing," says Fedchenko.Asia's Nuclear Power Boom
Today, most of the expansion in nuclear power generation is centered in Asia. The IAEA says that a total of 39 of the 64 plants currently under construction are located there.
Leading the Asian race to harness nuclear power is China.
At present, China has 13 operating nuclear power reactors, with 27 more currently under construction.
Beijing wants to both reduce its use of fossil fuels and costly imports of oil, and as the world's largest carbon emitter, it has promised to reduce its emissions by 2020.
It maintains that this cannot be done without massive development of nuclear power.
"The Chinese have been building nuclear reactors like hot cakes for five to 10 years, and they're going to continue to do this," says Mark Hibbs, another expert on nuclear policy at the Carnegie Endowment for International Peace.Concerns May Hamper Small Nations' Nuclear Ambitions
If China regards nuclear power as an integral part of its energy plans, so do many smaller developing countries.
The past decade of the global "nuclear renaissance" saw growing numbers of nations like Vietnam, Morocco and Indonesia announce they were considering plans to begin generating nuclear electricity by around 2020.
But the plans of those smaller states may be much more severely affected by the world's latest nuclear disaster than those of bigger countries.
Poorer states need to borrow the billions of dollars necessary to build plants from the international capital market and, after Fukushima, that could become more costly to do.
Acton predicts that the Fukushima crisis will raise the capital market's perception of the risk of investing in nuclear power.
"I think there also is going to be an effect [from Fukushima] on the growth of nuclear power," he says, adding that this will be particularly true of places "where governments don't buy power stations just out of their own pocket [and] where they have to go to the capital markets" to seek funding for power stations, including nuclear power plants.
Just how much rising borrowing costs could dampen developing countries' appetites for nuclear energy remains to be seen.
But the Fukushima accident only adds to the fears of those who question whether smaller states could ever afford to mount the kind of complicated rescue efforts now going on in Japan.
As the world watches the unfolding crisis at Fukushima, both critics and proponents of nuclear power can only feel a sense of dread that so many of the questions first raised by the Chornobyl disaster 25 years ago remain unanswered.
Can nuclear plants be made safe enough to prevent radiation leaks from malfunctions and natural disasters? And, once accidents occur, can rescue efforts sufficiently contain the radiation so it does not spread far and wide with the wind?
Such questions are likely to continue to accompany the development of nuclear power for decades ahead, even as more countries continue to embrace it despite the uncertainty.