northwestern Russia and Chazhma Bay near Vladivostok. The burial trenches have been evaluated to be secure for at least 600 years before the first pinhole penetration of some lead containment areas of the reactor compartment packages occurs, and several thousand years before leakage becomes possible. Prior disposal methods In 1959 the US Navy removed a nuclear reactor from the submarine and replaced it with a new type. The removed reactor was scuttled in the Atlantic Ocean, east of Delaware, at a depth of . In 1972, the London Dumping Convention restricted ocean disposal of radioactive waste and in 1993, ocean disposal of radioactive waste was completely banned. The US Navy began a study on scrapping nuclear submarines; two years later shallow land burial of reactor compartments was selected as the most suitable option. In 1990, was the first US nuclear-powered submarine to be scrapped. Future salvage work By the end of 2005, 195 nuclear submarines had been ordered or built in the US (including the NR-1 Deep Submergence Craft and , but none of the later ). The last of the regular attack boats, , was decommissioned in 2001, and , a highly modified Sturgeon, was decommissioned in 2004. The last of the initial "41 for Freedom" fleet ballistic missile (FBM) submarines, , was decommissioned in 2002. Decommissioning of the boats began in 1995 with . Additionally, a handful of nuclear-powered cruisers have entered the program, and their dismantling is ongoing. The first aircraft carrier due for decommissioning that would enter the SRP is planned to be , which was withdrawn in 2013. Unlike the disposal of other nuclear powered surface ships, all of which have been recycled at the Puget Sound Naval Shipyard and Intermediate Maintenance Facility, the Navy is looking at other, commercial or private sector options for Enterprise in an effort to reduce both the cost of the work and the time taken to dismantle such a large vessel, as well as negating the difficulty of towing the hulk all the way from Newport News, where it is stored, to Puget Sound. In December 2020, it was announced that a further nine Los Angeles-class attack submarines, two guided missile submarines, and the aircraft carrier would be decommissioned and enter the recycling program by 2026. Hulls waiting or already processed by the recycling program are listed below. Lists of vessels by type Aircraft carriers As of , Enterprise