[sefarkas]

The diesel generators were destroyed by the tsunami.

This is pure speculation. The diesels are housed in the same earthquake resistant, flood resistant building as the reactor equipment (details vary at each plant site, but the government regulations related to the emergency diesel generators are the same regardless of which plant you go to). It is possible that the cooling water for the diesels was affected by the tsunami and running the diesel with that water caused a problem; however, diesels are used in these applications specifically because they are rugged and durable and able to take some degree of abuse. The article above states with unusual certainty that the tsunami destroyed the engines -- I find the term destroyed a bit over the top and hard to believe.

[Errant]

I find the term destroyed a bit over the top and hard to believe.

I agree. It may be that the wave of water contaminated the fuel, lubricating oils or damaged supporting systems like cooling, supply lines, controls and etc.

If the engines were running at the time, they may have been damaged beyond repair. Certainly they must be in pretty bad shape, since they've not gotten them back into service by now.

Maybe at this site, they're located outside the buildings?

[PA Engineer]

This is pure speculation.

I thought the same thing at the beginning, but there is a before and after photo of the Fukushima nuclear plant. You can see the tsunami damage was extensive. The diesel backup survived the earthquake, but not the tsunami.

I find the term destroyed a bit over the top and hard to believe.

Are you a believer yet. The best engineering design for a tsunami is not to be in the way of it. They did not anticipate this one. I don't blame them.