The nuclear industry and its supporters have contrived a variety of narratives to justify and explain away nuclear catastrophes, writes John Downer. None of them actually hold water, yet they serve their purpose – to command political and media heights, and reassure public sentiment on 'safety'. But if it's so safe, why the low limits on nuclear liabilities?

Speaking at press conference soon after the accident began, the UK government's former chief science advisor, Sir David King, reassured journalists that the natural disaster that precipitated the failure had been "an extremely unlikely event".

In doing so, he exemplified the many early accounts of Fukushima that emphasised the improbable nature of the earthquake and tsunami that precipitated it.

A range of professional bodies made analogous claims around this time, with journalists following their lead. This lamentation, by a consultant writing in the New American, is illustrative of the general tone:

" … the Fukushima 'disaster' will become the rallying cry against nuclear power. Few will remember that the plant stayed generally intact despite being hit by an earthquake with more than six times the energy the plant was designed to withstand, plus a tsunami estimated at 49 feet that swept away backup generators 33 feet above sea level."

The explicit or implicit argument in all such accounts is that the Fukushima's proximate causes are so rare as to be almost irrelevant to nuclear plants in the future. Nuclear power is safe, they suggest, except against the specific kind of natural disaster that struck Japan, which is both a specifically Japanese problem, and one that is unlikely to re-occur, anywhere, in any realistic timeframe

An appealing but tenuous logic

The logic of this is tenuous on various levels. The 'improbability' of the natural disaster is disputable, for one, as there were good reasons to believe that neither the earthquake nor the tsunami should have been surprising. The area was well known to be seismically active after all, and the quake, when it came, was only the fourth largest of the last century.

The Japanese nuclear industry had even confronted its seismic under-preparedness four years earlier, on 16 July 2007, when an earthquake of unanticipated magnitude damaged the Kashiwazaki-Kariwa nuclear plant.

This had led several analysts to highlight Fukushima's vulnerability to earthquakes, but officials had said much the same then as they now said in relation to Fukushima. The tsunami was not without precedent either.

Geologists had long known that a similar event had occurred in the same area in July 869. This was a long time ago, certainly, but the data indicated a thousand-year return cycle.

Several reports, meanwhile, have suggested that the earthquake alone might have precipitated the meltdown, even without the tsunami – a view supported by a range of evidence, from worker testimony, to radiation alarms that sounded before the tsunami. Haruki Madarame, the head of Japan's Nuclear Safety Commission, has criticised Fukushima's operator, TEPCO, for denying that it could have anticipated the flood.

The claim that Japan is 'uniquely vulnerable' to such hazards is similarly disputable. In July 2011, for instance, the Wall Street Journal reported on private NRC emails showing that the industry and its regulators had evidence that many US reactors were at risk from earthquakes that had not been anticipated in their design.

It noted that the regulator had taken very little or no action to accommodate this new understanding. As if to illustrate their concern, on 23 August 2011, less than six months after Fukushima, North Anna nuclear plant in Mineral, Virginia, was rocked by an earthquake that exceeded its design-basis predictions.