At the time of her sinking, there were 99 crewmen aboard Scorpion. The boat contained a treasure-trove of highly sophisticated spy gear and spy manuals, two nuclear-tipped torpedoes, and a nuclear propulsion system. The best available evidence indicates that Scorpion sank in the Atlantic Ocean on 22 May 1968 at approximately 1844Z while in transit across the Atlantic Ocean from Gibraltar to her home port at Norfolk, Virginia.
Several hypotheses about the cause of the loss have been advanced. Some have suggested that hostile action by a Soviet submarine caused Scorpion‘s loss. Shortly after her sinking, the Navy assembled a Court of Inquiry to investigate the incident and to publish a report about the likely causes for the sinking. The court was presided over by Vice Admiral Bernard Austin who presided over the inquiry into the loss of Thresher. The panel’s conclusions, first printed in 1968, were largely classified. At the time, the Navy quoted frequently from a portion of the 1968 report that said no one is likely ever to “conclusively” determine the cause of the loss. The Clinton Administration declassified most of this report in 1993, and it was then that the public first learned that the panel considered that a possible cause of the malfunction was one of Scorpion‘s own torpedoes. (The panel qualified its opinion saying the evidence it had available could not lead to a conclusive finding about the cause of her sinking.) However, the Court of Inquiry did not reconvene after the 1969 Phase II investigation, and did not take testimony from a group of submarine designers, engineers and physicists who spent nearly a year evaluating the data.
USS Scorpion (SSN-589) was a Skipjack-class nuclear submarine of the United States Navy, and the sixth ship of the U.S. Navy to carry that name. Scorpion was declared lost on 5 June 1968 with 99 crew members dying in the incident. Later information confirmed that the Scorpion imploded at 18:42:33Z due to two low level explosions occurring at 18:20:43Z caused by the battery exploding. The hull collapsed due to a loss of depth control at a depth of 2015 feet. See information sent to the Navy by Bruce Rule on 22 Dec. 2008. See also “Silent Steel” by Stephen Johnson for more information. The USS Scorpion is one of two nuclear submarines the U.S. Navy has lost, the other being USS Thresher (SSN-593), which sank on 10 April 1963 off the coast of New England.
The U.S. Navy has periodically monitored the environmental conditions of the site since the sinking and has reported the results in an annual public report on environmental monitoring for U.S. nuclear-powered ships and boats. The reports provide specifics on the environmental sampling of sediment, water, and marine life that is done to ascertain whether the submarine has significantly affected the deep-ocean environment. The reports also explain the methodology for conducting this deep sea monitoring from both surface vessels and submersibles.
The monitoring data confirm that there has been no significant effect on the environment. The nuclear fuel aboard the submarine remains intact and no uranium in excess of levels expected from the fallout from past atmospheric testing of nuclear weapons has been detected by the Navy’s inspections. In addition, Scorpion carried two nuclear-tipped Mark 45 anti-submarine torpedoes (ASTOR) when she was lost. The warheads of these torpedoes are part of the environmental concern. The most likely scenario is that the plutonium and uranium cores of these weapons corroded to a heavy, insoluble material soon after the sinking, and they remain at or close to their original location inside the torpedo room of the boat. If the corroded materials were released outside the submarine, their large specific gravity and insolubility would cause them to settle down into the sediment.
source : http://en.wikipedia.org/wiki/USS_Scorpion_(SSN-589)

