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Japan’s nuclear shake-up

The death, injuries and extensive damage cased by the major 8.9 Richter scale earthquake in Japan are bad enough, but they are also having to contend with a nuclear crisis, on-going as I write.

Three of Fukushima Daiichi’s six Boiling Water reactors, and the four reactors nearby at Daini 200 miles or so north of Tokyo, were evidently in operation when the quake hit, at which point, WNN reported, they shut down automatically and commenced removal of residual heat with the help of emergency diesel generators. A small fire in an outbuilding at Daini was eventually extinguished

However, at Daiichi the emergency cooling pumps suddenly stopped about an hour after they were started, due it seems tsunami flooding. Portable power modules were then called in to replace the diesels and enable continued cooling, vital to avoid fuel meltdown. But pressure inside the core containment vessel, due possibly to leaking coolant, had evidently built up to a point where emergency venting was being considered “which will be filtered to retain radiation within containment.” As a precaution though evacuation plans were triggered and were later extended to 12 miles.

Then (early on 12 March UK time) there was a major explosion on the site, which some unconfirmed reports claim led to the partial destruction of an outer containment building. There had been earlier reports that internal radiation levels were at 1000 times normal, and unconfirmed reports that exposure rates outside the plant were at about 620 millirems per hour, about the same as the annual permitted exposure. But that may have been before the explosion, which some reports talking of a partial fuel meltdown.

Hard, verifiable, information is scarce, not least since it seems that key radiation monitors outside were disabled by the earthquake/tsunami. Although radiation leakage has been reported, the reactor core containment is said still to be intact, But if the cooling operation is not successful then there is a risk that, aside from the (hopefully low) possibility of a explosion as at Chernobyl, or a hydrogen explosion (as was feared at one time at Three Mile Island in the USA), melting fuel could burn through the core and the floor of the reactor building and enter the soil, a risk that would be heightened if the floor structure was cracked by the earthquake.

http://www.stratfor.com/analysis/20110312-red-alert-nuclear-meltdown-quake-damaged-japanese-plant?utm_source=redalert&utm_medium=email&utm_campaign=110312%284%29&utm_content=readmore&elq=464c899d2e6847429591aaa8baff429f

That’s all speculation at present, and hopefully the situation will be brought under control. But to make matters worse, there were warnings of possible secondary shocks and tsunamis.

Japan is prone to major earthquakes and buildings and other structures are designed accordingly, as was well demonstrated, they had done very well in this regard with few major building collapses. But the tsunami adds an extra dimension for structures on the coast, which is where the nuclear plants are located.

The major 7 reactor 8.2 GW Kashiwazaki-Kariwa complex in central Japan, was hit by a Richter scale 6.8 earthquake in July 2007, which fortunately only led to a relatively small (1200 litre, 90 k becquerel) radioactive leak into the sea. 400 drums of low-level waste were also dislodged in a store, with the lids of around 40 becoming open to the air, with it seems some radioactive gases being ventilated. A transformer unit also caught fire, and there were reports of 50 other problems, including broken pipes and radioactive water leaks. But all were said to be well below safety thresholds.

However, all seven reactors were closed and were off-line until recently.

A review of others around the country was initiated- most of Japans 55 reactors are only designed to withstand quakes of 6.5 – and of course, it’s not a linear scale, every unit increase in the Richter scale is ten times more in energy effect terms. An earlier proposal to raise the standard above magnitude 7.1 was shelved because of the high costs. That may now change.

After the 2007 episode, Japans Citizen’s Nuclear Information Center commented. “Japan is simply too quake bound to operate nuclear plants,” and there were calls for the closure of the reactors at Hamaoka- directly above a geologically active fault 60 miles West of Tokyo.

Hamaoka 4 and 5 were running at the time of the current earthquake but apparently were unaffected and are evidently still running at present, as are Kashiwazaki-Kariwa 1, 5, 6, 7, and Tomari 1, 2 and 3, but Onagawa 1, 2 and 3 automatically shut down as did the plant at Tokai, while WNN noted that the reprocessing plant at Rokkasho is being supplied by emergency diesel power generators.

It’s hard to say what will happen next in terms of nuclear power in Japan – it all depends on the unfolding events at Fukushima.

Posted by Dave Elliott on March 12, 2011 2:50 PM | Permalink