Although it was a 1960's design, the reason it failed the way it did was because of one design flaw...
Its backup generators were not placed up on the hills above it. Rather, the backup generators were situated below sea level underneath the reactor buildings. DERP.
Fukushima Dai-ichi survived the Magnitude 9 earthquake. It did not survive the tsunami because said tsunami overcame the tidal wall in front of it, and then the backup generators got flooded. But for that one event, if the generators were placed up on higher ground, the outcome would have been so much different.
I have first-hand knowledge, due to..
1) Knowing the area. I lived in my Japanese father-in-law's mountain house, situated 1.5km out of Miyakoji-machi, Tamura-shi. That town was just inside the 20km evacuation zone from the power plant, the mountain house was just outside at 21km - myself and my family lived in our own house in the outskirts of Koriyama city.
2) My (now deceased) Japanese father-in-law was president of the Hitachi subsiduary company which built Fukushima Dai-ich No.4 reactor, which wasn't operating at the time of the earthquake and subsequent tsunami but did suffer an explosion thought due to hydrogen gas from the spent fuel situated in the Spent Fuel Pool in its upper level.
3) Mentioned in point (1) above, I owned a house in Tobu New Town on the Eastern outskirts of Koriyama city, and I was working at Flextronics in Koriyama at the time the M9 quake occurred - things got a tad 'exciting' at the time. I should write a book.
My point is that nuclear power is safe, as long as all disaster scenarios are taken into account - in Fukushima Dai-ichi's case, for some reason (possibly financial?), it was decided that the tsunami barrier was sufficient (it wasn't) for the job, and at some point in time it was decided that placing backup generators underneath the buildings was sufficient - that unfortunately did not turn out to be the case :/
And lastly, I still fully support the idea of nuclear power.