Nuclear power and the Japan earthquake

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A gigantic natural disaster, the like of which has not been seen there in over a thousand years, has hit Japan last Friday. A magnitude 9.0 earthquake shortly followed by a massive tsunami has left 10 000 victims dead and millions homeless and without water. No country in the world is as well prepared for and safeguarded against just this kind of calamity as Japan is. Had it happened anywhere else with comparable population density, the number of casualties would have been at least ten times higher. This is a time for help and not for the party political point scoring Germany is currently engaged in.

In spite of that I do not agree with those, who see the current focus on the nuclear power stations as frivolous and out of place. An earthquake like that is more than anyone can reasonably plan for and a partial release of the fission product inventory as has happened in Chernobyl would be far more disastrous in the small and populous country of Japan with nowhere to go. In spite of everything else it is essential to focus on this threat first.

So let us do just that. According to current information three reactors have been so badly damaged, they are not likely ever to run again. In spite of the known risks of a site directly on the shoreline all the emergency generators were sited in a way, that they could all be incapacitated by the wave. This still left a running emergency system with battery power for many hours, but in spite of Japan’s technological sophistication and the availability of everything imaginable in very short distances they failed to restore power in time. So going by what is known now, it seems that just like Three Mile Island a bad situation was made worse by inadequacy and incompetence.

That is the one side of it. The other is this: In all cases and in spite of the hydrogen explosion destroying an outer building both the reactor vessels and the containments have staid intact. There was some release of activity, something to be expected when venting primary coolant even with an undamaged core. The dose rate is said to have reached several hundred times the permissible rate. This sounds bad but during a common chest X-ray you are exposed to about twenty million times the natural background. Admittedly the higher rates found near the plants in Japan will last longer than a second, but they are not permanent and will be gone in a few weeks. The permissible rate is based on someone living right next to the plant all their lives and getting all their food and water from there. Also everyone from the whole area has been evacuated to a distance of at least 20 km for the time being. From what is known now nobody outside the emergency teams on site is likely to receive a significantly higher dose than that of a holiday flight to Europe and back.

Things in Japan are not good and there doubtlessly is real danger. To put that in perspective imagine a chemical plant like Seveso, like Bhophal or like the innocuous seeming Bayer plant right next to where I am living exposed to even a much smaller earthquake. Or, to stay in the same line of business, think of the effects on a coal mine or a drilling platform like Deepwater Horizon. It is of course far too early for any final conclusion, but if events so far show anything, it is the safety and reliability of nuclear power. The ecological effects until now are decidedly less than those from oil refineries and other contamination sources.

Update Monday, 2011-03-14

Looking at what information I can find, the Japanese plants do not have the (nearly) spherical steel containments common in Germany and able to withstand tremendous pressure. They seem to be made from far more brittle reinforced concrete and in complicated shapes with plane surfaces and sharp corners. According to an ambiguous announcement by the IAEA the explosion on Friday has resulted in the loss of the containment of Fukushima Daiichi Unit 1. If that is indeed the case, If they were to be breached, then the pressure vessel is the only remaining barrier for the presumably destroyed core. On the plus side residual heat will have gone down a lot by now, but it is still in the order of several MW and the only means for removing it seems to be the boiling off and venting of coolant. If the containment is indeed broken that means the loss of filtering for the vented gases.

In an update the IAEA has clarified that the explosions in units 1 and 3 did not damage the containments. On Tuesday, March 15th, the containment of unit 2 was breached. There is also serious doubt about the long term integrity of this unit’s reactor vessel so this is currently the most critical plant. Evacuation of all personnel due to high radiation may make the situation uncontrollable.

It is extremely hard to come by reliable information about what is actually happening in Japan. The best overview is probably that by the nuclear engineering students at MIT. The best German summary of events I could find is by the physicist Kai Petzke. A reasonable summary of events in English is by Mike Tucker in Wall Street Journal and the Washington Post also has quite sound reporting. Then there are the IAEA, the GRS and the Wikipedia community.

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