A big tsunami like that happens about once every 500 years. It the life of the nuclear plant is 50 years, the risk of a disaster happening was 1/10. I don't think that this was an acceptable risk. Even a risk of 1/100 or 1/1000 would be unacceptable.

That means that the nuclear plant should have never been there, or should have been prepared to be run over by a tsunami...