Japanese Nuclear Watch Update – One Meltdown, Another Probable, Large Evacuations Ordered

6:54 am in Uncategorized by Bill Egnor

This cutaway diagram shows the central reactor vessel and thick concrete containment in a typical boiling water reactor of the same era as Fukushima Daiichi 1 (image: www.world-nuclear-news.org)

First, thanks much to our great commentors — Masoninblue, earlofhuntingdon, Professor Foland and many others — who continue to provide updates and expert analysis on the Japanese nuclear crisis. And hat tip to commentor “lobster” for finding a better schematic that helps illustrate the conflicting stories about a “meltdown.” [Updated to reflect suggestions for clarity.]

You can find other articles at the these links:

Explosion At Quake Damaged Fukushima Nuclear Power Plant

Facts On What A Melt Down Is

Japan Nuclear Watch – Struggling To Prevent Meltdowns

Disaster is not too strong a word for what has happened to Japan in the last three days. The biggest earthquake recorded, the subsequent massive tsunami and now the follow-on of at least two partial meltdowns of nuclear reactors at Fukushima and the critical status of three more there, and others in the nation.

Let’s start with a little vocabulary so things are as clear as they can be in this confusing situation. When I talk about the “Reactor Vessel,” I am talking about the stainless steel bottle where the fuel and control rods are housed. This also includes the entire pressurized system for generation of electricity as it is a closed single loop system.

When I talk about the “Reactor Building,” that is a concrete structure primarily designed to keep the weather off of the reactor and generator equipment. It was not designed to be another sealed radiation containment building like AT some of the plants elsewhere the in the world.

That said, let’s talk about what we do know. Reports vary but between 200,000 and 450,000 people have been ordered evacuated from the area around the Daiichi and Daini power stations. The Daiichi complex is the older of the two with 6 reactors built in the 1970’s and Daini has 4 reactors built in the 1980’s

It is the Daiichi Unit Number 1 that has experienced the explosion (more on that shortly) and has been the focus of an attempt to cool the reactor core with seawater. Reports have come in that Unit Number 3 there has also had a complete failure of the emergency cooling system and rods are exposed to a level of three meters. (more after the jump)
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