Fukushima spent fuel pool No.4

The magnitude 7.3 earthquake that occured off the coast of Japan last Friday was widely reported. What wasn’t reported at all was the effect that this earthquake might have had on the already badly damaged Fukushima Daiichi nuclear plant. I’m not going to speculate on the reason for this media blackout, but will add that yesterday, Murata Mitsuhei, Japan’s former Ambassador to Switzerland, sent an e-mail to chief editors of newspaper and tv companies and other influential people, warning that the Fukushima unit 4 fuel pool is in danger of either draining or collapsing. No one took a blind bit of notice of Mitsuhei. So what’s all the fuss about unit 4 fuel pool..? Here’s a photo of unit 4 reactor building, taken shortly after the disaster began…

The long crane that can be seen in the photo was used to pump water into the spent fuel pool, which was in danger of draining due to damage caused by multiple explosions at the plant (there’s lots of speculation that during the early days of the crisis the No.4 pool did drain completely for a while). If the pool drains or collapses, and the fuel rods become exposed to air for any length of time, there’s every likelihood that the rods will catch fire. This fire would be very difficult to put out, because of nuclear/chemicle reactions taking place and incredibly high levels of radiation. The other three damaged reactor buildings also have fuel pools, but they contain old fuel rods. The problem with No.4 fuel pool is that the fuel rods had only recently been taken out of the reactor. Spent fuel rods still give off a lot of heat and have to be cooled for anywhere between 3 and 5 years after they’ve been removed from a reactor. This cooling is achieved by placing the rods in pools and circulating water around them.

The damaged units at Fukushima Daiichi are Mark 1 boiling water reactors, built 40 years ago by General Electric. The design of these Mark 1 types has the fuel pool above the reactor, about 100 feet in the air (the fuel pool is like a very deep swimming pool). Unlike the reactor itself, the fuel pool has no containment structure. It’s just the water in the pool that separates the fuel rods from the environment. The danger with No.4 fuel pool is that it is a badly damaged structure, situated in an area with high seismic activity, and could collapse with the next earthquake (I’m sure I don’t need to point out how crazy it was to site nuclear reactors in such an area). The fuel rods need to be removed from the pool and put in a place of safety as soon as possible. Problem is, you can’t just lift ‘hot’ fuel rods out of a pool and put them somewhere else, because of the heat and radiation hazard (when fuel rods are removed from a reactor and placed in the cooling pool it is all done under water). The solution is to use what’s known as dry cask storage. The rods are placed in these casks and inert gases are pumped into them, so that the rods can’t catch fire; but the casks weigh up to 100 tons and thus need heavy lifting equipment. The Tokyo Electric Power Company (TEPCO), who operate the Fukushima plant, are in the process of building a new structure above the No.4 fuel pool, in order to install a large crane. The following is a TEPCO diagram showing what they are doing. It’s not a particularly good diagram, yet it does give some indication of the proximity of the fuel pool to the reactor and the ground (the bulbous shape, lower left, is the reactor)…

The last I heard, TEPCO reported that they will be able to start removing ‘hot’ fuel rods from No.4 pool in 2014. The big worry is, as last week’s 7.3 magnitude earthquake showed, will such a damaged structure remain standing that long? So, what happens if the fuel pool does collapse before all the rods are removed..? Firstly, you’ll have a fire that is very, very difficult to extinguish. Secondly, a huge amount of radiation will be released into the environment. Thirdly, the high radiation levels will necessitate the entire Fukushima Daiichi plant being evacuated, which will mean that crisis management of the three reactors that have melted down and the other fuel pools will have to be abandoned. The whole lot will go up in smoke, radioactive smoke. There are 1,532 fuel rods in No.4 pool (weighing about 90 tons) which contain roughly 37 million curies of long-lived radioactivity. To put this into context, a radiological fire from a collapsed No.4 pool would release almost 10 times more cesium 137 than Chernobyl. In total on the Fukushima Daiichi site there are more than 11,000 spent fuel rods, containing about 336 million curies of long-lived radioactivity. The cesium 137 component of this is roughly 85 times more than was released by Chernobyl.

If, God forbid, the No.4 fuel pool does collapse it’s difficult to speculate on what the effects would be, because this is totally unchartered territory (as is three reactors that are side by side going into total meltdown). It’s safe to assume that most of Japan and parts of nearby countries would become uninhabitable because of radiation. The effects on the rest of the world can only be guessed at. I don’t think it would be an extinction level event, but an awful lot of people will die as a result of it.

Here’s former Ambassador Murata Mitsuhei, speaking in September via a video link at the Coalition Against Nuke’s Congressional Briefing. Murata’s command of the English language is at times comical. What he’s talking about is deadly serious…

If you were interested enough to listen to the above talk by Murata Mitsuhei here’s part of what he said:

Originally, Japan had a maternal culture characterized by harmony and solidarity. After the Meiji Restoration was introduced to Japan, a paternal culture characterized by competition and confrontation in military form. History shows that paternal cultures end in catastrophe. Fukushima is the result of the supremacy of economy, another form of paternal culture introduced after WW2. The Maternal culture of harmony is the remedy for the paternal culture of power.

I’ll be making a future post about this maternal and paternal culture stuff.

This entry was posted in Politics, Science and tagged , , , , , , , . Bookmark the permalink.

Leave a Reply

Your email address will not be published.