I think the story goes that the US was offering to helo in gensets on day one to get cooling back-up before everything went pear-shaped ... but made it conditional on the japs shutting down and dismantling the reactors after everything was hunky-dory ... the japs had just extended the lease on these things for another 10 years although they were originally due to be decommissioned this year (the oldest is 40 years old) ...Anyone understand this? What would the US have done again? Dismantle? Don't they have to solve the same problems before they can dismantle?
... and why on earth were they loading up these past use-by reactors with MOX, a last hurrah?
.. the japs said no thanks we'll go it alone as they wanted to reserve right to start them up again once they were back in control, they never got cooling back-up and well the rest is history ...
... i don't think they ever fully comprehended what they were dealing with, these are the guys that were mixing fuel by hand in stainless-steel buckets to save pennies a few years back. Probably, just local plant operators who have not been exposed to the full dangers involved in the complete fuel cycle and they got tied up in the minutae of operations when they were in a do or die situation. Normally they just load fuel in and load it out and run the reactor to well-defined procedures, this was well outside the square and they should have been brave enough to lose face and accept outside help.
UK had windscale fire, US had Threemile island, USSR had chernoble ... it seems like they have to go through this to get a visceral feel for them what it is like when they let the nuclear fission beast out of the cage ... now they know.