The 'official' account as well as the Power magazine report seems to focus on the fatigue cracks on the cover flange and bolting, This does not explain the upward forces lifting the 1500T assembly through the roof. The article in the International Water Power & Dam Construction, Dec. 22, 2010, offers a more plausible theory of a water hammer as the main source, see http://www.waterpowermagazine....sp?storyCode=2058518
If true, there is nothing to prevent the disaster happening again. The new turbines' installation started within months, so it is very likely to be of the same design. That the design is very poor considering the loading pattern, is quite evident. The same design weaknesses will remain.
The result of a proper RCA must be prevent recurrence, not find people to blame.