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Is nuclear power just a ticking timebomb?

Amid the apocalyptic scenes reaching our television screens from northern Japan, it seems invidious to address just one aspect of this catastrophe or to draw any conclusions - so recently did disaster strike and so comprehensive is the destruction.

Already, however, the disaster has posed with a new urgency a question that seemed to have been retreating from global concerns in recent years: how safe, really, is nuclear power?

Japan, given its history, had every reason to be among the most circumspect countries in developing and harnessing nuclear power. Its geography argued for double, treble the precautions that might be taken anywhere else. And until last week, the safety measures appeared more than adequate.

Japan had a safety record, and a reputation for integrating safety into design, that was second to none. The famed national discipline and resilience of the Japanese was seen as an added asset, in the event of anything untoward.

Until now, it had also been possible to cite Japan's experience to rebut fears about the safety of nuclear reactors.

There was always something particular about previous nuclear accidents that would not, it was assumed, be replicated in Japan. America's worst nuclear accident, at Three Mile Island, was the consequence of a mechanical failure that caused the reactor core to overheat. New regulations and design changes followed. The most destructive of all nuclear accidents, at Chernobyl, in Ukraine, whose 25th anniversary - by a cruel quirk of fate - will be commemorated in just one month, reflected shortcomings in design, but also the neglect of infrastructure and general indiscipline that attended the last years of the Soviet Union. Nuclear power in Japan, it was widely accepted, was at a whole different level of reliability.

All assumptions about the safety of nuclear power must now be open to challenge. Maybe it will turn out that there was more that Japan's regulators could have done to ensure the safety of the reactors at Fukushima.

Already some are highlighting criticisms voiced previously in Japan, alleging trade-offs between safety and cost.

It is also possible that the extensive safety measures that were in place minimised the escape of radiation.

Even the best-case scenario, however, will not suffice to allay the doubts about nuclear power that have nagged so many for so long.

Granted that this was a natural disaster far off the scale of anything ever envisaged, even for Japan's fragile geology, the implications are still grave.

If the Japanese, with all their understandable inhibitions about anything nuclear and all their world-leading technology, cannot build reactors that are invulnerable to disaster, who can?

It can come as no comfort to the people of Japan as they count the cost in lives, property and damage to the country's environment to consider that the massive earthquake was never a matter of "if" but always a matter of "when".

Located at the meeting point of three major tectonic plates, Japan is recognised as one of the most seismically active areas of the world.

This particular earthquake ripped along a 500km segment between the Eurasian and Pacific plates causing massive tremors, numerous after-shocks and a 30ft tsunami wave.

So was Japan prepared? Ingenious systems have been developed which allow the immediate shutting off of some power grids, gas pipe flows and rail systems to prevent additional disasters such as moving trains derailing and ruptured gas pipes exploding.

Fire stations are fitted with doors that can open automatically on detecting the first tremor of an earthquake, to ensure that essential fire fighting services can get their vehicles out of the station when the shaking has finally stopped.

There are also widespread public awareness campaigns on earthquake evacuation drills and risk reduction initiatives in homes.

Staring at our television screens, we inevitably are struck by the enormity of what Japan is facing and ask questions.

Why were vehicles still moving along coastal roads as the tsunami wave hit? Had the warnings been too late or were they ignored?

As Japan responds to this disaster their government has sensibly called for external assistance.

Key tasks will include the search for and rescue of people trapped in buildings or in flooded areas.

Many thousands have been made homeless and will need shelter, food, medical care and support. Communication networks will be stretched as families and friends in Japan and overseas try to find out if their loved ones are safe.

Casualty handling and tracking by the authorities will be a massive task as many are hospitalised, moved to reception centres or find shelter elsewhere, while the task of identifying the many dead will also need to begin.