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Abandoned Russian nuclear power plant.

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Physics Today

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Dr. Dick van der Wateren



Nuclear disaster

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New nuclear accident magnitude scale highlights catastrophes

05.01.2012, Age: 3582 days

Four recent nuclear catastrophes, Chernobyl, Three Mile Island, Fukushima and Kyshtum, feature prominently in a new nuclear accident magnitude scale developed by the British Emeritus Professor of Geophysics David Smythe.

The new scale shows that four nuclear accidents - Chernobyl, Three Mile Island, Fukushima and Kyshtum - are in a class of their own. They are 100 to 1000 times bigger, using the new magnitude measure, than any other accidents of the last 60 years. In addition, such catastrophic accidents are more frequent than predicted by the old scale. One can be expected to occur every 12 to 15 years.

The existing scale for nuclear accidents (INES - International Nuclear Event Scale, devised by the International Atomic Energy Agency in 1990) has been shown to be inadequate to deal with major nuclear accidents. Since the Japan earthquake and tsunami last March many people have been asking; why is Fukushima classed (finally) on the scale at the same level 7 as Chernobyl ?; why does the scale stop at level 7? The details of the new scale have just been published online in the prestigious US physics journal Physics Today. It is based on the Richter logarithmic scale of earthquake magnitude.

Professor David Smythe (Emeritus Professor of Geophysics, University of Glasgow) said:

"It is time to stop relying on an inadequate nuclear industry scale which was designed explicitly for PR purposes, and is deliberately non-quantitative. The ceiling limit of level 7 artificially suppresses the true magnitude of some accidents. My new scale is quantitative; it is very simple to calculate if the radionuclide release data are available; it is logarithmic like the so-called Richter scale of earthquake magnitude; and it has no theoretical upper or lower limits.

I have calibrated the scale to match the existing one. The new magnitudes are, in decreasing order:

Chernobyl (Russia 1986), M=8.0;
Three Mile Island (USA 1979), M=7.9;
Fukushima Daiichi (Japan 2011), M=7.5, and
Kyshtym (USSR 1957), M=7.3.

The remainder of the 33 accidents that I have been able to quantify are all of magnitude 5.2 or lower, that is, over 100 times less significant. There are many more possible accidents which remain undiclosed, secret, unrecorded, or unquantifiable, but even without these, the basic predictions of the new scale are robust.

Just as with earthquakes, a large magnitude is not necessarily indicative of more damage. But with the new scale, which I call NAMS (Nuclear Accident Magnitude Scale) we now have an objective measure of the fundamental feature of serious accidents which concern the public - the release of harmful radionuclides into the atmosphere."

Professor Smythe told the COSIS.net News Editors:

"Although I have lived in France for the last eight years, I am currently challenging the UK government's intention to site a high-level nuclear waste repository in West Cumbria. My interest in nuclear accidents arose from this recent work, although I first became interested in the issue when I heard Sir Douglas Black lecture in Edinburgh about childhood leukaemias at Sellafield, nearly 30 years ago."

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