There have been all sorts of problems over the years...makes me think of the film Silkworm.
I fear very little was learnt about safety culture from Tōkai where they carried around Uranium solutions in buckets.
This seems to be a common problem, but whenever I've heard of operational sites (in many different industries and countries) relying on their backup diesel generators, they often start and a little while later fail. The last occasion I heard of was due to the diesel fuel freezing due to the outside temperature. -> What was the temperature at Fukushima yesterday morning?