Appended below is the white paper which accompanied the release of the reports on SCORPION and THRESHER. The actual reports discussed in the following paper are not yet available electronically. CAPT Tim Taylor, USN Email: Tim.Taylor@ncts.navy.mil Navy Office of Information Phone: 703-695-2078 DSN 225-2078 Washington, DC 20350-1200 Fax: 703-697-2767 DSN 227-2767 - Please send NavNews email to navnews@opnav-emh.navy.mil - ---------------------------------------------------------------- The Navy Public Affairs Library (NAVPALIB) A service of the Navy Office of Information, Washington DC Send feedback/questions to navpalib@opnav-emh.navy.mil ---------------------------------------------------------------- Here is the complete text of the "white paper" released by the Department of the Navy on 25 Oct 1993: U.S. NUCLEAR POWERED SUBMARINES LOST AT SEA Two U.S. Naval nuclear-powered submarines were lost at sea in the Atlantic Ocean, USS THRESHER (SSN 593) in 1963 and USS SCORPION (SSN 589) in 1968. Neither loss involved a reactor accident. Interest has recently been renewed about the environmental condition of these submarines. The Navy has periodically monitored the environmental conditions of the sites since the sinkings and reported the results in an annual public report on environmental monitoring for U.S. Naval nuclear-powered ships. Details of the monitoring expeditions in 1983 and 1986 are contained in reports now being made available by the Navy. In the case of SCORPION, this report confirms that two nuclear tipped torpedoes were aboard when the ship was lost. These reports provide specifics on the environmental sampling of sediment, water and marine life which were taken to ascertain whether the submarines have had a significant effect on the deep ocean environment. The reports also explain the methodology for conducting deep sea monitoring from both surface vessels and submersibles. THE MONITORING DATA CONFIRMS THAT AFTER OVER 18 YEARS THERE HAS BEEN NO SIGNIFICANT IMPACT ON THE RADIOACTIVITY IN THE ENVIRONMENT AT EITHER SITE. Nuclear fuel in the submarines remains intact and the surveys at the SCORPION site found no plutonium in excess of levels expected from fallout from past atmospheric weapons testing. Detailed still photographs and video footage of the submarines on the ocean floor are also being made available by the Navy. The video and most of the still pictures were taken by the submersible ALVIN and the remotely operated vehicle JASON JR (Woods Hole Oceanographic Institute submersibles) during the last environmental monitoring expedition. This information serves to fully describe the current environmental condition of these submarines and enhance the body of knowledge on techniques for deep ocean environmental monitoring. USS THRESHER (SSN 593) The U.S. nuclear powered submarine THRESHER sank April 10, 1963 in approximately 8,500 feet of water about 100 miles east of Cape Cod. THRESHER is in six major sections on the ocean floor. The majority of the debris is in an area of about 400 yards square. The major sections are the sail, sonar dome, bow section, engineering spaces section, operations spaces section, and the tail section. Comprehensive deep ocean radiological monitoring operations were conducted in August 1983 and August 1986 at the THRESHER site. The THRESHER site had been previously monitored in 1965 and 1977 and none of the samples obtained showed any evidence of release of radioactivity from the reactor fuel elements. Very low concentrations of cobalt 60 in the form of corrosion products from THRESHER piping systems were detected in sediment. Cobalt 60 is the predominant activated corrosion product found in the reactor coolant piping system on U.S. nuclear powered warships. Therefore, it was the primary radio-nuclide released when the coolant piping system aboard THRESHER was breached. The conclusion of the earlier surveys was that THRESHER had not had a significant effect on the radioactivity in the environment. The purpose of the monitoring in 1983 and 1986 was to identify whether radiological conditions had changed and to demonstrate the use of improved sampling and navigation equipment deployed from both a surface ship and a deep ocean submersible. The 1983 and 1986 surveys confirmed the conclusion of earlier surveys. Fission products were not detected above concentrations typical of world wide fallout levels in sediment, water, or marine life samples. Thus, there continues to be no evidence of release of radioactivity from the reactor fuel elements. Cobalt 60 concentrations in the sediment were generally lower than those found in 1977 as would be expected due to radioactive decay. No cobalt 60 was detected in the large number of fish and other marine life specimens or in undisturbed water samples collected at the THRESHER site. This confirmed that cobalt 60 in the form of insoluble corrosion products is not concentrated in the deep sea food chain. No uranium was detected above background levels from natural radioactivity and world wide fallout from past atmospheric weapons testing. The maximum cobalt 60 concentration detected in the sediment was 0.32 pCi/gm and most samples contained much less. This is approximately a factor of 100 lower than the concentration of naturally occurring radioactivity in sediment. For perspective, if a person's entire diet contained cobalt 60 at the maximum concentration detected in the sediment at the THRESHER site, that person would receive less than five percent of the radiation exposure typically received from natural background radioactivity. The 1983 and 1986 survey results confirm that THRESHER has not had a significant effect on the radioactivity in the environment. The reactors used in all U.S. Naval submarines and surface ships are designed to minimize potential hazards to the environment even under the most severe casualty conditions such as the actual sinking of the ship. First, the reactor core is so designed that it is physically impossible for it to explode like a bomb. Second, the reactor fuel elements are made of materials that are extremely corrosion resistant, even in sea water. The reactor core could remain submerged in sea water for centuries without releases of fission products while the radioactivity decays, since the protective cladding on the fuel elements corrodes only a few millionths of an inch per year. Thus, in the event of a serious accident where the reactor is completely submerged in sea water, the fuel elements will remain intact for an indefinite period of time, and the radioactive material contained in these fuel elements should not be released. The maximum rate of release and dispersal of the radioactivity in the ocean, even if the protective cladding on the fuel were destroyed, would be so low as to be insignificant. Radioactive material could be released from this type of reactor only if the fuel elements were actually to melt and, in addition, the high-strength, all-welded reactor system boundary were to rupture. The reactor's many protective devices and inherent self-regulating features are designed to prevent any melting of the fuel elements. Flooding of a reactor with sea water furnishes additional cooling for the fuel elements and so provides added protection against the release of radioactive fission products. A report of the 1983/1986 environmental monitoring expeditions to the THRESHER site is available and provides details of the environmental sampling of sediment, water and marine life which were taken to ascertain whether THRESHER has had a significant effect on the deep ocean environment. It also explains in detail the methodology for conducting deep sea monitoring at the THRESHER site from both surface vessels and submersibles. USS SCORPION (SSN 589) The submarine SCORPION sank May 22, 1968 in more than 10,000 feet of water about 400 miles southwest of the Azores. SCORPION is in two major sections. The forward hull section including the torpedo room and most of the operations compartment is located in a trench that was formed by the impact of the hull section with the bottom. The sail is detached. The aft hull section including the reactor compartment and engine room is located in a separate trench that was formed by the impact of the hull section with the bottom. The aft section of the engine room is inserted forward into a larger diameter hull section in a manner similar to a telescope. NUCLEAR WEAPONS: There were two Mark 45 ASTOR torpedoes with nuclear warheads aboard SCORPION when she was lost in 1968. The warheads were low-yield tactical nuclear weapons. The special nuclear material from the warheads has not been recovered. The most likely scenario is that the plutonium and uranium core of these weapons has corroded to a heavy, insoluble material soon after the sinking and remains at or close to its original location inside the torpedo room of the submarine. If the corroded materials were released outside the submarine, their large specific gravity and insolubility would cause them to settle in the sediment. ENVIRONMENTAL MONITORING: Comprehensive deep ocean radiological monitoring operations were conducted in August and September 1986 at the SCORPION site. The SCORPION site had been previously monitored in 1968 and 1979 and none of the samples obtained showed any evidence of release of radioactivity from the reactor fuel elements. Very low concentrations of cobalt 60 in the form of corrosion products from SCORPION piping systems were detected in sediment. Cobalt 60 is the predominant activated corrosion product found in the reactor coolant piping system on U.S. nuclear powered warships. Therefore, it was the primary radio-nuclide released when the coolant piping system aboard SCORPION was breached. The conclusion of the earlier surveys was that SCORPION had not had a significant effect on the radioactivity in the environment. The purpose of the monitoring in 1986 was to identify whether radiological conditions had changed and to demonstrate the use of improved sampling and navigation equipment deployed from both a surface ship and a deep ocean submersible. The 1986 survey confirmed the conclusion of earlier surveys. Fission products were not detected above concentrations typical of world wide fallout levels in sediment, water, or marine life samples. Thus, there continues to be no evidence of release of radioactivity from the reactor fuel elements. Cobalt 60 concentrations in the sediment were generally lower than those found in 1979 as would be expected due to radioactive decay. No cobalt 60 was detected in the large number of fish and other marine life specimens or in undisturbed water samples collected at the SCORPION site. This confirmed that cobalt 60 in the form of insoluble corrosion products is not concentrated in the deep sea food chain. The maximum cobalt 60 concentration detected in the sediment was 1.16 pCi/gm and most samples contained much less. This is over a factor of ten lower that the concentration of naturally occurring radioactivity in sediment. For perspective, if a person's entire diet contained cobalt 60 at the maximum concentration detected in the sediment in the vicinity of the SCORPION site, that person would receive less than ten percent of the radiation exposure received from natural background radioactivity. SPECIAL ENVIRONMENTAL MONITORING FOR SPECIAL NUCLEAR MATERIAL: Sediment, water, and marine life were analyzed for plutonium isotopes using very sensitive mass spectrometry techniques. The concentrations of total plutonium were not significantly different than the background concentrations due to fallout from past atmospheric nuclear weapons testing. Additional discussion is found in the SCORPION site environmental monitoring report. The 1986 survey results confirm that the SCORPION has not had a significant effect on the radioactivity in the environment. The reactors used in all U.S. Naval submarines and surface ships are designed to minimize potential hazards to the environment even under the most severe casualty conditions such as the actual sinking of the ship. First, the reactor core is so designed that it is physically impossible for it to explode like a bomb. Second, the reactor fuel elements are made of materials that are extremely corrosion resistant, even in sea water. The reactor core could remain submerged in sea water for centuries without releases of fission products while the radioactivity decays, since the protective cladding on the fuel elements corrodes only a few millionths of an inch per year. Thus, in the event of a serious accident where the reactor is completely submerged in sea water, the fuel elements will remain intact for an indefinite period of time, and the radioactive material contained in these fuel elements should not be released. The maximum rate of release and dispersal of the radioactivity in the ocean, even if the protective cladding on the fuel were destroyed, would be so low as to be insignificant. Radioactive material could be released from this type of reactor only if the fuel elements were actually to melt and, in addition, the high-strength, all-welded reactor system boundary were to rupture. The reactor's many protective devices and inherent self-regulating features are designed to prevent any melting of the fuel elements. Flooding of a reactor with sea water furnishes additional cooling for the fuel elements and so provides added protection against the release of radioactive fission products. A report of the 1986 environmental monitoring expedition to the SCORPION site provides details of the environmental sampling of sediment, water and marine life to ascertain whether SCORPION has had a significant effect on the deep ocean environment. It also explains in detail the methodology for conducting deep sea monitoring at the SCORPION site from both surface vessels and submersibles. -USN-