Concur. Due to its design, the fuel assemblies (rods?) at Chernobyl actually smelted themselves and released evaporated radioactive elements, including metals, directly into the air. This was due to it using graphite for a moderator. It burned, the steam piping ran in vertical openings in the graphite pile, and the burning graphite got a pretty effective chimney effect going.
3-Mile Island melted at least the upper half of the fuel rods, due to lack of cooling water. Moron operator keept turning off pumps when they automatically came on. He was trained in-house by the utility. First-rate Navy-trained operators cost too much for them, so they got a $6-billion cleanup bill.
At Fukushima, they lost offsite power due to the eatrhquake, and internal power due to automatic shutdown because of the earthquake. Then the 6-15 foot tall wave drown out their diesel generators. Pathetic engineering, as this was a readily forseeable scenario. Japan holds tsunami drills all the time.
Without power, the decay heat of the used fuel boils off the water. If you don't replace the water, the fuel melts. One small firetruck could have delivered enough make-up water by suctioning from the seawater intake canal, and pumping into the the steam system. It all would have run back into the reactor. The firetruck method has actually been tried at a BWR before: look up "Brown's Ferry fire".
My guess is that the main problem in Japan was an inability to make a decision in a timely manner. The Japanese culture is to mull problems over for days, hold several meetings, discuss it over drinks, and finally achieve some sort of consensus -- in a week or three.
"Reactor desparately needs water NOW -- pump water into reactor. Only have seawater, and it will ruin the entire system -- system will be ruined tomorrow by the impending meltdown -- start pumping seawater."
It just took them too long to acknowledege the inevitable. And we in the USA may have that same lack of alacrity in a big emergency, if the utilities persist in training for Normal Ops, and leaving out ugly emergencies. The Navy trains for the hard stuff first, thus they develop superb operators.
"It ain't Rocket Science, it's just a big teakettle with some pecularities"