[bombcar]

So it sounds like you'd need something on both sides of the "glass" kind of like this aquarium magnet but much larger/complicated: https://www.amazon.com/JRing-Aquarium-Cleaner-Aquariums-Clea... and slowly move it around the whole tank, repeatedly scanning as it goes.

So I'm going to put it in the "theoretically possible but nobody will do it" category for now. ;)

[jacquesm]

It's a much harder problem than that. Even if you did not find the crack just before taking the structure into use a crack could develop at any point in time after that and you're definitely not going to be emptying this tank on a regular basis for inspection.

So you either detect it before commissioning or it will eventually fail if there is a flaw.

[chmod775]

They had divers regularly going inside to clean it anyways. Doesn't seem like such an unlikely thing.