As part of nuclear training a few years ago (I had a Senior Reactor Operators license on a US Westinghouse 3 loop plant), I remember seeing the electrical switchgear on at least one plant was flooded as it was below ground level.
The plant I worked at had the emergency diesels at ground level and the diesel fuel oil tanks were buried. At full load, I remember 5 gpm fuel usage or 300 gallons per hour (the day tanks were 330 gallons Tech Spec as I recall). We had a large storage tank above ground level that could make up to the buried fuel oil storage tanks.
Whenever we did testing that ran the DGs, fuel oil was soon ordered.
With no switchgear, it made no difference if the DGs ran, you couldn't get the power to the pumps.
When you have multiple failures like this, it means crappy design.
From a link: >At the four damaged nuclear power plants (Onagawa, Fukushima Daiichi, Fukushimi Daini and Toka Daini), 22 of the 33 total backup diesel generators were washed away, including 12 of 13 at Fukushima Daiichi. Of the 33 total backup power lines to off-site generators, all but two were obliterated by the tsunami.
Unable to cool itself, Fukushima Daiichi’s reactors melted down one by one.
“What doomed Fukushima Daiichi was the elevation of the EDGs (emergency diesel generators) inexplicably and fatally low, Synolakis said.
LINK: Fukushima was preventable
Last I saw about Diablo Canyon is that they plan on shutting them down in 2025.
Thanks for the info! IIRC Diablo Canyon’s replacement steam generators were crap.