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SSN-571 Nautilus - Refueling

NAUTILUS operated until May 1979 after 2500 dives and 513,000 miles. Nautilus cruised 62,562 miles on her reactor's first core, 91,324 miles on the second, and 150,000 miles on the third. By February 1957, USS Nautilus had run as far as her first loading of fuel would allow. The boat had traveled 62,562 miles, more than half of them submerged. She had hosted royalty, entertained political leaders, and convincingly played the role of a high-speed enemy submarine in Navy war games. Now she sailed home to Groton, Connecticut, for the delicate process of removing the reactor core and replacing it with a new and better one.

Fuel in the unshielded core emitted gamma radiation so intense that a few moments of close exposure would cause death. The procedure to remove the core from the boat was pre-planned in endless detail. The objective was to move the core into a shielded transport cask and hoist the cask onto a truck. This conceptually simple but highly complex task took two months to accomplish. Nautilus then sailed away to the Pacific Ocean, and the old core was sent across the country to Idaho.

One issue for the Navy was the long life of the reactor and its fuel. Changing fuel in the cramped spaces of a submarine was extremely inconvenient, not to mention hazardous. Replacing the entire core was worse. The boat had be dry docked while welders cut open the skin of the boat and removed the reactor the same way a surgeon might remove a bad appendix. The procedure would tie up the boat for up to two years, hardly the place for a weapon system during war or an international crisis.

The first two cores for both the S1W prototype and NAUTILUS were operated in the 1950s. The first S1W prototype core (S1W-1) operated from March 1953 until September 1955. The second prototype core (S1W-3) operated between March 1956 and November 1957. The first NAUTILUS core (S1W-2) operated from December 1954 until February 1957. The second NAUTILUS core (S1W-3A) operated between April 1957 and May 1959. After each refueling the NAUTILUS cores were sent to NRF where the S1W prototype facility and ECF were located.

The fuel used in the first two cores for both the S1W prototype and NAUTILUS was highly enriched uranium. The S1W plant also operated with some removable fuel assemblies that were installed and removed throughout the lives of the two cores. The vast majority of the spent fuel associated with the cores, including the removable fuel assemblies, was ultimately sent to ICPP for reprocessing to recover valuable highly enriched uranium.

The uranium recovery information from specific Idaho Chemical Processing Plant (ICPP, currently called INTEC) processing campaigns cannot reliably be used to account for all of the fuel from these early spent cores. For example, shipments of S1W-1 fuel to ICPP started in 1956 and continued up to as late as 1963. In any given calendar year in the late 1950s and 1960s fuel shipped to ICPP would have come from several different spent cores. Another flaw in the approach of comparing spent core uranium inventories to ICPP uranium recovery was that some of this spent fuel was sent to other laboratories for evaluation. Other laboratories that received some spent fuel specimens included Bettis Atomic Power Laboratory, Knolls Atomic Power Laboratory, Oak Ridge National Laboratory, Battelle Memorial Institute, Argonne National Laboratory, Brookhaven National Laboratory, and General Electric-Hanford.

Due to the military significance of Naval nuclear propulsion, much of the information specifically associated with the S1W prototype and NAUTILUS cores is classified and cannot be discussed in detail in publicly available documents.

The first NAUTILUS core (S1W-2) was received at NRF in March 1957. Disassembly of the core for inspection, sampling and disposition occurred between April and July 1957. The fuel was prepared for reprocessing by removing the non-fuel structural components of the fuel assemblies in the water pit at S1W. The second NAUTILUS core (S1W-3A) was received at NRF in 1959. The fuel was prepared for reprocessing by removing the non-fuel structural components of the fuel assemblies at the ECF water pit.

The first S1W prototype core (S1W-1) was initially retained at NRF after refueling. The fuel was prepared for inspection and reprocessing by removing the non-fuel structural components of the fuel assemblies in a water pool in the S1W building. In addition, smaller portions of the fuel to be examined for testing purposes were sent to a hot cell in the S1W building.

The second S1W prototype core (S1W-3) was removed from the plant in November 1957 and transferred to the S1W water pit for disassembly, inspection, and disposition. In addition, smaller portions of the fuel to be examined for testing purposes were sent to a hot cell in the S1W building.



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Page last modified: 07-02-2016 19:42:03 ZULU