Q-

"Unless temperatures are recorded by the sensors connected to the spent fuel pools, they are suspect."

Thanks for pointing this out.

I tend to agree with you that this event was beyond the reasonable assumptions of the designers, who did add a safety margin.

I do believe that when the design assumptions were greatly exceeded by the earthquake and tsunami, the fact that there were four reactors overwhelmed at once compounded the job of the on-site workers. I'm also convinced that mistakes were made in the initial attempts to mitigate the conditions in the runaway reactors and spent fuel pools. But we'll only learn the details 5 or so years from now, and by that time the public will only remember Fukushima and maybe a date. If you told people in general that half the fuel at Three Mile Island had melted down and escaped the reactor vessel, how many people would already know that; the report came out 5 years later.

Gnu-

I also find the report from NHK on reactor Unit 1 perplexing:

"Temp went up to 400... seawater injection doubled... pressure went up and temp went to 330... pressure down somewhat... 'steady' now... "

There should be such spikes of temperature if this reactor is really back under control.

mg-

I'm not sure how they "clean house" in Japan but the job needs to be done and most likely will be done. They probably have to depend on nuclear power for the seeable future and they can't afford to make this kind of dreadful mistake.

Charley Noble