Japan's nuclear plants had been switched off after the meltdown at the Fukushima plant in March 2011 caused by a tsunami following an earthquake. More than 100,000 people were evacuated from the surrounding area.
This switch-back-on will be the first of many.
But, after one of the most shocking incidents in nuclear power's history, four experts talk to the BBC World Service Inquiry programme about whether we can continue to live with the technology.
Tatsujiro Suzuki was vice-chairman of the Japanese government's Atomic Energy Commission at the time of the Fukushima disaster. He is now director of the research centre for nuclear weapons abolition at Nagasaki University.
"I thought [Fukushima] would be the end of the nuclear industry in Japan: it was very shocking.
"I personally felt very responsible for the event and I felt very sorry for the Fukushima people. It was not just a technical issue. This kind of accident has a serious social, ethical, political impact on their lives.
"We expected that there would be no such serious accident in Japan. In our culture if you speak of the devil he will show up. So you better not speak the bad thing. There's no Japanese translation of the word 'risk', so there's no 'risk analysis' or 'risk assessment': we call it 'safety analysis', 'safety assessment'.
"In the public mind there was no clear connection between the peaceful use of nuclear energy and nuclear weapons. Most people in Japan are against nuclear weapons, but the majority of the public were not against nuclear power.
"As you saw pictures of the explosion and people evacuating from their homes and becoming concerned about radiation, people started to think this could have the same impact as nuclear weapons. Finally, people started to realise radiation is radiation.
"It is a huge, huge loss of public trust. It's going to take a long long time to recover it."
Miranda Shreuers is director of the Environmental Policy Research Centre at the Free University in Berlin. She was asked to join the commission to determine Germany's nuclear policy after the Fukushima disaster.
"Germany had always looked at Japan as a peer, a country of similar technological capacity, so the question was really, could something like that happen in Germany?
"After Fukushima, Germany reached something that you don't find in many other countries that have nuclear energy: a cross-party consensus that nuclear is not the future. That lies with other areas, with energy efficiency, with smart cities, with new technologies.
"We're going to phase out nuclear energy and, at the same time, phase out of other fossil fuels: so a double phase-out, that really is historic.
"Germany has a history of division, so there was always concern that there could someday be new conflict, and concern about the connection between conventional nuclear and military purposes of nuclear.
"That contributed in the 1970s to the development of an environment peace movement and anti-nuclear movement that came together in a much stronger way than it did in most other places.
"The best thing that Germany can do is to present an alternative model that is very likely to be the more attractive model to populations around the world if we can show that it is, in fact, doable.
"I find it hard to imagine that Germany could ever again live with nuclear power."
Gabrielle Hecht is professor of history at the university of Michigan.
"Certain state elites in South Africa, Kenya, Nigeria and Ghana are reprising the language that you saw in the 1950s elsewhere in the world, in India, in France, in the United States: a modernising enthusiasm that nuclear electricity would be easy, cheap and could spread very easily.
"There is this kind of sense that nuclear power will provide a kind of infinite amount of energy for people, for homes, for industrial development, and the details are - as with earlier generations - being passed over by this generation as well.
"The prospect of having abundant electricity in places where there are very often electricity brownouts and blackouts, and where large parts of the country are not electrified, is huge.
"[But] even in South Africa where you have the most robust infrastructure, and you have at the moment, a very strong government backing for this, and you have at least promises of financing from the Russians, from the Chinese, there is still a lot that can go wrong and stop this course of action.
"[The risks from] political change, the collapse of financing, assessments showing the investments that you'd have to make in the national electric grid are really too huge, other industries coming in and saying, 'for much less money we could build a big solar array, we could build a wind farm', mean it still looks looks very contingent.
"I think that we're going to have to live with nuclear power, but I think that we should try to stop doing so.
"There are nuclear power plants operating now, and it would be crazy to just stop them all tomorrow, although there are certainly activists who would like to do that.  I don't think that's particularly realistic. But do we have to build new ones? No, there are better ways to invest our time and efforts as societies."
Steve Kidd is now a consultant, after working for the World Nuclear Association and its predecessor organisation the Uranium Institute (UI) for almost twenty years.
"I believe nuclear does have an important part to play in energy in the 21st century, but I've become increasingly pessimistic about its ability to take on that role that's been left open for it.
"That's because of what I describe as the paradigm of fear. The whole history of nuclear power since 1945 has been dominated by a fear factor. It is scary, dangerous, and ought to be treated with a great degree of caution. This fear factor is heavily influencing the economics so that the plants have become extremely expensive to build.
"The fear that people have has an impact on the political process and ultimately on the regulatory regime, so the requirements on the building of nuclear power stations have become more and more difficult to fulfil. Not all of the cost escalation can be put down to fear, but it is an important factor.
"We've just had the 70th anniversary of the bombs dropped on Japan. The link between nuclear power and nuclear bombs has always been very difficult to shake off.
"The industry has tried to counter that with a factional approach, almost saying to the public, 'you're stupid, you're irrational', but in fact the development of their beliefs has been wholly rational, based on what they've seen and heard over the years, and something like the Fukushima accident obviously gives credence to such fears.
"I think the industry quite naturally felt that if people had the facts at their disposal - and the facts on nuclear are very, very favourable to it - they would suddenly become hugely supportive of it, but that comes up against the problem that it's ultimately people's beliefs that determine their opinions."
The Inquiry is broadcast on the BBC World Service on Tuesdays from 12:05 GMT/13:05 BST. Listen online or download the podcast.
As Japan restarts its nuclear power industry four years after the Fukushima disaster, have we learned to make peace with the technology?