The explosions at the Fukushima nuclear plant have reignited the debate about the acceptability of nuclear energy. A debate which, for the best part of a decade, had been swinging solidly behind the idea of a new generation of nuclear power stations in many countries.
It is quite easy to make a case that Fukushima is not really relevant to the current debate about new nuclear power stations: the stricken reactors were commissioned between 1970 and 1979 essentially using 1960s technology. Modern plants depend far more on 'passive cooling', using natural air flow, than on engineered safety systems such as pumps and valves.
The reactors even largely withstood the earthquake - flooding because of the tsunami caused the problems. And perhaps most significantly, the inner containment, the steel pressure vessel, are withstanding the extraordinary stresses to keep the spent fuel contained, though there have been measurable releases of radioactive materials. Indeed, just up the coast, refugees from the devastation took shelter in the Onagawa nuclear plant, the safest building for many miles.
Like Three Mile Island, supporters of nuclear energy can reasonably claim that the incident demonstrated just how robust the structures are.
And yet the safety of older plants will rightly be revisited. Questions will be asked as to whether the designers of modern plants have thought of everything. There will be claims that a slice of luck prevented the accident from being thus far more severe, and anyway there were radioactive releases beyond legally acceptable limits, though probably not enough to hurt the broader public.
Like Three Mile Island, opponents of nuclear energy can point to the risks this accident highlights. And public opinion, always labile over 'back-of-the-mind' issues like nuclear power, could turn against the industry as quickly as it had come to support it.
What will Japan - a country to which the future, in terms of energy reserves, has come early - do if not nuclear? Oil spillages in the Gulf of Mexico, unrest in the Middle East, Russian export policy and petrol prices make oil, and its partner gas, unattractive. Coal reserves are limited and climate change is a major concern. As for wave power, tidal power or offshore wind, they would presumably have been ripped from the ocean bed by the earthquake, and washed away by the tsunami, representing losses of power - and therefore life in the emergency conditions - for months if not years.
Rare accidents of the Fukushima scale may be an inevitable consequence of the use of nuclear energy - though many lessons have been learned since they were designed and built. If other alternatives were dramatically better we'd all be using them by now. The consequences for modern societies of not having enough energy, or of destroying the environment with greenhouse gases, probably outweigh the problems with any particular fuel. Tough choices are not made any easier - for or against nuclear power - by the recent events in Japan.