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The reactor accident at Fukuashima

Overall I think that Fukuashima is a serious accident but it is not as bad as Chernobyl.  (https://markforeman.wordpress.com/2011/05/21/chernobyl-and-fukuashima-which-is-worse/)  The two accidents are very different, Chernobyl was a nasty big steam explosion caused by a surge in the heat production caused by nuclear fission. This power surge was caused by a combination of operator error and a very poor design, after the steam explosion a series of fires increased the amount of radioactivity which was lost from the plant. The technical term for a Chernobyl like event is RIA (Reactivity Initiated Accident), just because an accident is a RIA does not mean it will be a super serious accident. A RIA event occurred at SL-1 in the USA, this was a small research reactor which had a steam explosion which killed three men.

The kitchen version of a RIA is dropping an egg, like a RIA the dropped egg accident occurs all at once. The accident is sudden and may include mechanical damage.

The accident in Japan is a Loss Of Cooling Accident (LOCA), this is the nuclear reactor version of sticking an egg in a frying pan, turning on the heat and leaving it to burn. LOCA accidents tend to subject the nuclear fuel to less mechanical violence, so as a result the isotope signatures of a LOCA and a RIA is likely to be different. While neither a LOCA or a RIA is good, I think that the LOCA is likely to cause a radiologically less horrible release. Below is a bar chart showing the isotope signatures for the Japanese accident and Chernobyl. These bar charts have been adjusted to make the Cs-137 bars the same size.

Part of the isotope signatures of the Chernobyl and Fukushima accidents

It can be seen that the Sr:Cs ratio for the Chernobyl release is richer in strontium, as strontium-90 is more toxic than cesium-137 this makes the Chernobyl fallout (assuming that chemical fractionation does not occur for the fallout for either accident) more harmful to health for a given activity. The lack of Mo-99 and Ru-106 in the Japanese release also suggests that some of the transport mechanisms which liberated fuel at Chernobyl have not been operating in the Japanese accident.

I will be adding more content soon, this page is a work in progress. If you have any technical data about the event then please feel free to contact me by means of a comment. In the meantime feel free to look at my blog for posts on the topic.

 Good well written comments will be printed. While feelings may be running high over the morality of nuclear power plants, please understand that I will neither be approving comments which are simple political slogans.

If you feel like closing down all nuclear power plants next week then while you are entitled to your point of view, I will not print any comments unless you can back up your point of view clearly in a short bit of text. As I am evenhanded I will also refuse to print comments like “build 100 new PWRs in china”. If you want to build lots of nuclear plants then you are also entitled to a point of view, but just like the antinuclear comments a pronuclear comment which is unsupported will remain unseen by my readers.

When we think about the nuclear accident it is important to divide up the stages of the accident. I have divided up my posts on the subject into the following groups for your ease.

1. The beyond design basis event

The great problem with a beyond design basis accident is that it involves an event which none of the design team thought was a reasonable event. For example if I was to suggest the following events.

Jörmungandr (Large mythical sea snake) attacks the water intakes for a Swedish nuclear power plant and thus disable the cooling systems, while at the same time Fenrisúlfr enters the switch yard and knocks down a series of poles thus causing a station blackout.


A group of Kappa derail a train and smash open the used nuclear fuel flask in a populated area (maybe they have grown tired of their normal knavish tricks)

You might wonder what on earth am I thinking of. While both ideas are very far fetched, I choose very unlikely events (the animals attacking the nuclear plants and the fuel shipment are unlikely to exist). While these events are rather unreasonable events, lesser events involving animals have occurred at nuclear sites. For example seagulls at Sellafield are known to spread contamination around and I have read of one sea mammal which entered a lake of seawater used by a power plant for cooling. In the latter case if I recall it correctly the worry was that if the water level in the lake dropped then the animal might get sucked up a pipe like Augustus Gloop (See Charlie and the Chocolate Factory, R. Dahl). Rather than just getting stuck in a pipe the worry was that the body of the animal might damage machinery. In the end the animal left the lake without having been sucked up.

In the Japanese case it was a extra large earthquake which created a giant wave which started the accident. While some defects in the design may have made the accident worse, the core of the event was an event which could not be imagined by most people. Like many things I imagine that no single person is responsible for the misadventure, instead a series of latent flaws existed in the power plant and the organisation. On one fateful day the holes aligned and then the accident occurred.

2. The events inside the reactor buildings

As the world knows the reactors inside three units have been badly damaged, the degree of damage is not clear to all. During the early stages of the accident some reports circulated suggesting that some form of nuclear explosion occurred in a used fuel pond. I hold the view that a nuclear detonation in a fuel pond is very unlikely to have occurred.




3. The escape of radioactivity



4. The transport of radioactivity from A to B


5. How the radioactivity affects society

6. What is society doing about the radioactivity, and also what can society do about it.

I have seen a range of suggestions regarding the accident, one blogger wants leading members of TEPCO and other organisations to appear before the ICC, which I think is a bad idea. I hold the view that the ICC does not cover industrial accidents and that Japanese courts should deal with the civil cases and any criminal cases.


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