It appears that the construction defects in some of the Virginia class submarines may not be as worrying as previously thought:

Both Northrop Grumman Shipbuilding and General Dynamics Electric Boat have conducted exhaustive analysis and testing that demonstrates: the low probability of improper welds occurring aboard submarines; that improper welds are unlikely to fail during the ship’s operational life; and that should a weld fail it would leak but not break, thereby alerting the crew in time to address the issue before the weld degraded further.

That sounds reassuring.

Note that this is separate from the issues involving bolts for the weapons handling system.