A Japanese earthquake that forced the closure of the world's biggest nuclear plant has highlighted the energy source's dangers, just when support had been growing. Worries about security of energy supply and the urgency of fighting climate change had helped to overcome years of opposition to nuclear power after the 1986 Chernobyl disaster.
Generating nuclear power does not produce any of the carbon emissions blamed for warming the planet. But even for those swayed by environmental considerations, there are obstacles and, for the doubters, Japan's troubles have added to their unease.
"It's bound to have an effect. Chernobyl had a huge effect. These things are all factors into the equation. The question is about the balance? Will the public disquiet counteract the huge push by the industry?" asked Frank Barnaby, a consultant at the Oxford Research Group, who argues nuclear power is not worth the risk.
A powerful earthquake on July 16 caused radiation leaks, forcing Tokyo Electric Power Co (TEPCO) to shut its Kashiwazaki-Kariwa plant in the north-west of the country. The Nuclear Energy Agency (NEA), advisory board to the OECD, said the biggest impact would be higher safety standards.
"The real impact will be that, logically, people designing new nuclear power plants will pay even more attention to the criteria for seismic events," said Luis Echavarri, the NEA's director, speaking by telephone from Paris.
Other difficulties varied from country to country. In Europe, public opinion was the dominant factor, although to an extent it had been won over, Echavarri said.
"Nuclear energy is much more popular than a few years ago because of climate change and security of supply, but still in some countries, it's politically difficult."
Although public opposition has been relatively muted, the government has been forced to review its nuclear energy policy by a court challenge from environmental group Greenpeace. At the same time, it is becoming harder to maintain Britain's ageing fleet.
British Energy, which hopes to play a big part in building any new nuclear plants, had to shut down its Hunterston and Hinkley Point nuclear stations for lengthy repairs and has said they are unlikely to return to full power. Like Britain, the United States, the world's biggest energy user, is also thought to be well on the way to seeking new nuclear plants and applications for licences are expected to be submitted later this year.
Regardless of TEPCO's difficulties, US analysts said the fundamental reasons for looking to nuclear remained in place. There could be an impact on public confidence, they said, but the time needed to process plans could be a bigger hurdle.
"These plants are so far away from being built. Who knows what factors could affect policy-makers between now and then?" Denise Furey of Fitch Ratings, said. Sweden and Germany are among the nations that have decided to phase out nuclear power. Both have experienced problems with Swedish firm Vattenfall's nuclear facilities.
In Sweden a reactor at the Forsmark plant suffered an emergency shutdown in July last year. It was rated two on the International Nuclear Event Scale (INES), compared with seven for the Chernobyl disaster, the world's worst nuclear accident. For INES factbox, please click on
Vattenfall's German unit Vattenfall Europe is also under scrutiny following two emergency shutdowns and the German government has threatened to withdraw operating licences for the plants involved.
The incidents have been especially sensitive in a country where nuclear plants have met massive popular resistance, leading the previous government to agree to the closure of all of Germany's reactors by the mid-2020s.
Those most favourable to nuclear power include Finland and France and both are building new plants. In France nuclear power provides around 80 percent of the nation's electricity needs and generally has public acceptance because it means cheaper power.
But even France has its nuclear detractors. After last week's earthquake in Japan, the nation's anti-nuclear association Sortir du Nucleaire said 42 of France's 58 nuclear power reactors might not be able to cope should a similar incident occur in France. Most analysts say, however, that is extremely unlikely.