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Weightman Report

My Lords, I have a little familiarity with the Fukushima event but I have not yet had the privilege of reading Dr Weightman’s report. However, it is worth making a few comments. First, I make no comment on the relationship between the operating company and the regulatory authority in Japan or indeed on the way in which the plant was operated. However, it is worth recognising that the Fukushima plant was actually designed 50 years ago and constructed around 40 years ago. Both of these dates are before the days of modern computers, which is an astonishing advantage that one has when one is designing a modern nuclear plant. Anyone looking at the issue carefully today, although with hindsight we have all sorts of bright ideas how things could have been better, is impressed at how well this ancient—almost fossil—nuclear plant came through an event that was far beyond the design specifications agreed at the time that it was built. It was built to withstand a tsunami of five metres high. In the event, it had to withstand something over 12 metres. It is worth emphasising the extreme improbability of the event that faced Fukushima. The earthquakes of the magnitude that hit Fukushima occur something like once every 25 years somewhere along the 40,000 kilometres of the Pacific rim. But that was not the only remarkable event. The second event—or the second coincidence, if you like—was that it had to be approximately where it was, 200 kilometres off the coast. Had it been much closer to the plant, there would have been much less effect. There would have been much less water available to push in the tsunami. If it had been further out, the tsunami would have been much more widely dispersed. So effectively it required two rather exceptional events. I do not know that anyone has satisfactorily computed the probability or improbability of this sort of thing happening, but it is very, very small. I do not think that it really ought to influence our nuclear debate one way or another. That said, when there is a nuclear accident, there are always lessons to be learnt, and I am sure we shall learn design ideas or get new ideas on the basis of what has happened.