August 6, 2012: Last May 23rd there was a fire inside the USS Miami (a Los Angeles class SSN or nuclear attack submarine) while it was in the Portsmouth (Maine) Naval Yard for maintenance and upgrades. That blaze did $400 million in damage to the sub and seven people were injured. Two months later a shipyard worker was arrested for setting the fire. The accused worker, Casey J. Fury, admitted that he set the May 23rd fire and another on June 16th (which was quickly extinguished) in order to get out of work early. Casey was seen near the June 16th fire and that led to his being questioned more closely. Casey knew he had a problem and checked himself into a mental hospital on June 21st and left on June 23rd. The question now arises as to how a guy like this was allowed to work on a nuclear submarine. It could be sloppiness, union politics, or fear of federal regulators (there is a growing list of questions you cannot ask when hiring people) or a combination of all these factors. Also, the U.S. Navy has been complaining for a long time about incompetent management of naval shipyards. That bad behavior is protected by politicians more interested in reelection than well run yards.
Meanwhile, the 22 year old Miami is liable to be scrapped. Maine politicians are trying to avoid that but part of that effort involves coming up with over $400 million for the work, at a time when the defense budget is shrinking. The U.S. Navy is also shrinking
It's not just fires that these old Los Angeles class boats have to worry about. Three years ago a 25mm (one inch) hairline crack was found on the pressure hull of the (then) 14 year old USS Toledo. The crack was in the metal plate, not a weld. After carefully examining the crack the plate was replaced. Above the crack there was a 53 cm (21 inch) hairline crack in the outer (non-pressurized) hull, which was under the sail. The USS Toledo had just undergone a three year refit, costing $179 million. The sub was sent to a nearby (to New London, Connecticut) shipyard for the repairs. At first it was thought some of these cracks were related to a recent scandal where shipyard workers failed to check for substandard welds but that was not the case with the Toledo.
Such a crack in the pressure hull is a serious problem because it makes it more likely that the pressure hull would fail and flood the boat, at less than the "test depth" (about two thirds the "design depth," which is the maximum depth the sub can operate at). Going a little deeper gets you to the collapse (or "crush") depth, at which the pressure hull is crushed and implodes. The deepest diving U.S. subs, the Seawolf class, are believed to have a test depth of 490 meters (1,600 feet) and a collapse depth of 730 meters (2,400 feet). During World War II collapse depths were never more than 320 meters (a thousand feet). Since then, larger boats, built of stronger metals, have greatly increased the depth subs can operate at. But that only works if the crew knows the limits of their boats, and cracks in the pressure hull reduce those limits.
Both the Miami and the Toledo were among the latest "improved Los Angeles" boats. If the Miami were retired, a much older (in terms of technology) boat would have to delay retirement and fill in. Upgrading one of these older boats would also be expensive. The navy is putting much of its cash into building new Virginia class boats to replace the 42 (of 62) remaining Los Angeles subs. The most recent of these entered service in 1996, and will be gone by the end of the next decade. Nine Virginias are in service and another 21 are planned. If the navy can scrounge up enough cash it can build two a year and have all the Virginias in service before the Los Angeles class is gone.