Fukushima Compared to TMI and Chernobyl

This item places the presentdisaster in proper perspective and eliminates a couple of issues.

First the reactors are now wellon the way to cooling down to safe levels, though just like TMI, partial meltsin the core caused immense damage. However, we can expect three of the reactors to be taken apart almostroutinely or at least mostly so.   Onehowever is likely suffering from a lot of fused metal and will not be routine.

Second, the pleasant surprise isthat the plant itself was literally a month from decommissioning which explainsthe lack of proactive steps after the danger report two years ago, or ratherthe action was the planned shutdown and decommissioning.  We just got unlucky.

Third, the plant was thus surplusto Japan’sneeds and its loss must be not be particularly significant.

The tsunami risk was not properlyplanned for and why this should be so escapes me.  All reactors need to be evaluated for thisobvious risk.  At the least critical backup power can easily be installed in an upper floor of a stout building emplacedbehind the reactors.

All plants of this nature shouldbe located behind barrier islands. Please observe, the quake took place many miles from shore, yet theeffects on land only affected severely the coastal area of Honshu.  Did anyone notice on the west coast?

Vancouver happens to have a subsiding platedirectly west of its location, yet there is little evidence of major tectonicactivity in the past ten thousand years. Surely this is because Vancouver Islandacts as ballast to absorb all such shocks and its west coast is practicallyuninhabited.  We still know little aboutearthquake prediction, but simple physics can isolate promising areas that willusually be safer than others it coastal building is required.

Disaster Note Fukushima

By Mikka Pineda for Roubini

This year marks Chernobyl's 25thanniversary, and how ironic it is that the world has a new nuclear emergency onits hands: Japan's Fukushima power plant, operated by TEPCO. Thesituation at Fukushima continues toworsen, with explosions at two more reactors and the radiation releasedsurpassing that of Three Mile Island. The40-year-old reactors, designed by General Electric, were due fordecommissioning at the end of this month.

The Fukushimanuclear incident will likely be upgraded from a level 4 to a 5 on theInternational Nuclear and Radiological Event Scale. The scale runs from 0 to7—the most severe. The incident will remain "an event with localconsequences," although this excludes the consequences for the expansionof nuclear power generation around the world. Three MileIsland was a level 5; Chernobylwas a level 7—the only level 7 event so far.

The 1986 Chernobyl disaster, causedby design flaws and operator error, spewed radioactive graphite and clouds overUkraine and Belarus and reached as far as Sweden.The first country to detect the emergency was Russia which, in itspre-Glasnost days, neglected to notify the world and did not begin evacuationuntil 36 hours after the first explosion. Firefighters and liquidators (cleanupworkers) were inadequately informed about and equipped for the dangers theywere facing. The cleanup took decades and is not over yet—180 tons ofradioactive material remains sitting in a concrete sarcophagus over the plant.The sarcophagus cracked last year and is emitting radioactive gases. In 2011,the 25th anniversary of Chernobyl, thesarcophagus will be replaced with another shell financed by a multinationalfund (Ukraine is still reeling from the ongoing costs of Chernobyl and lacksenough funds to replace the shell alone). The total cost of resettlinginhabitants, cleaning and sealing the area and paying off medical claims isestimated by Belarusto be around US$235 billion—add to that another billion or two to replace thesarcophagus.

In 1979, Pennsylvania’s Three MileIsland (TMI) power plant experienced a cascade of events more similar to thoseof Fukushima.TMI was a pressurized water reactor; Fukushimawas a boiling water reactor. There's little difference between the twoinsofar as both used water to cool and regulate the reactors, except that TMIhad a pressurizer. Like Fukushima, Three MileIsland Unit 2 (TMI-2) was vented into the air to reduce pressure in the core,releasing some fissile products (Cesium-137 and Iodine-131—the sameproducts released from Fukushima).TMI-2 also experienced a small hydrogen explosion, which tore off the exteriorwalls of the containment building, and a partial core meltdown. Cleanup costUS$975 million and took 14 years to complete.

The problem with light water reactors in general isthe vicious cycle of needing to vent coolant to relieve pressure andthen having less to cool the core, which progressively generates more heat andpressure that then needs to be relieved. If the core heats up enough, thezirconium cladding around the core causes the water to release hydrogen. Thehydrogen builds up outside the reactor vessel, eventually causing theexterior walls of the containment building to explode.

Add to this the problem with Fukushimain particular, which is that once the main power supply (the nuclear plant) isshut off—in this case because the earthquake triggered an automatic shutdown—the reactorsstill need an alternative power supply to run thecooling systems. Fukushima 1'sbatteries last only eight hours, and the emergency diesel generators lastedonly a total of 24 hours.

Now that the core is damaged and seawater has been poured over thereactors to cool them, Fukushima 1 (and possiblya plant in Tokai as well) are damaged beyond repair—resulting in a permanentloss in Japan'spower supply. If things don't get much worse, cleanup efforts and medicalclaims for Fukushimawill be similar to those of TMI. The radiation exposure of the civilianpopulation so far remains light, and iodine tablets were promptly distributedto counteract any radioactive iodine released. Though those tabletsonly prevent thyroid cancer, so far only around 8,000 microsieverts havebeen detected outside the plant—far below the one sievert minimumfor radiation sickness.

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