One of the most useful sources of information on Fukushima is Barry Brooks’ Brave New Climate, where he reports on the cooling tanks for spent rods:
The problem is that as these ponds heat, their deep covering of water (which acts as a radiation shield and a cooling mechanism), starts to evaporate. If they reach boiling point, because of lack of operational maintenance systems, the evaporation rate will accelerate. If exposed, there is a potential for these old fuel rods and their zirconium cladding to melt, and radiation levels will rise considerably. . . . The spent fuel pool temperature has been rising gradually since last Friday due to the loss of cooling pump (presumably no power source).
Sure, the pump may not work — ’cause a vandal (known as The Tsunami) took the handle. But why is it so difficult to keep a pool refreshed with water? It’s not as if it’s Olympic-sized.
The Japanese finally brought in firefighting vehicles to douse the rods. Then, in a desperate, if dramatic move, the Japanese used helicopters to fetch water from the ocean and bombard the plant with it.
Last night on MSNBC’s Hardball with Chris Matthews, former head of the U.S. Nuclear Regulatory Commission Jeffrey Merrifield mentioned that the Japanese made a critical mistake in overlooking the evaporating pool problem while attending to more pressing matters (presumably the explosions). As a consequence what seems like the simplest task — keeping pools filled with water after the pump has broken — has snowballed into a national emergency.