Shifting focus to the "spent fuel pools" at the Fukushima Complex and her is a link to a new graphic at Wikipedia which shows where they are located in this design: click here for update!

Each reactor has its own spent fuel pool and its located rather high up in the building which surrounds the reactor and its primary containment. Given there location they would appear to be highly vulnerable to the kind of explosions that have already taken place at Units 1, 2, and 3. After 40 years of operation they would be packed with still highly radioactive "spent fuel" rods, and if their coolant is lost through a breach or evaporation, they could indeed catch fire.

Evidently the spent fuel in Unit 4 did catch fire earlier today but the company claims that the fire was successfully put out. I'm puzzled why there was such a problem in this unit when it was already in cold-shutdown status, unless no one noticed that the spent fuel pool was no longer being supplied with coolant until it was too late.

There have been a number of human errors that have contributed to the unfolding catastrophe at Fukushima Complex 1. It's understandable that the workers might make errors in such an unprecedented emergency, but such errors have consequences. Evidently the workers at the neighboring Fukushima Complex 2 have been more successful in stabilizing their four reactors.

When this accident is reviewed I predict that its primary causes will be attributed to:

Failure to design the complex to the standards needed to survive a level 9 earthquake and tsunami

Human error in trying to stabilize the reactors after the cooling pumps failed.

Unlike other technologies for producing energy, nuclear energy is intolerant of major design failures and human errors, and the consequences can be catastrophic.

Charley Noble