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Military

Nuclear Propulsion

Decommissioning and Defueling

US Navy nuclear ships are decommissioned and defueled at the end of their usefueli lifetime, when the cost of continued operation is not justified by their military capability, or when the ship is no longer needed. The Navy faces the necessity of downsizing the fleet to an extent that was not envisioned in the 1980's before the end of the Cold War. Most of the nuclear-powered cruisers will be removed from service, and some LOS ANGELES Class submarines are scheduled for removal from service as well. Eventually, the Navy will also need to decommission 0HIO Class submarines.

US Navy nuclear-powered ships are defueled during inactivation and prior to transfer of the crew. The defuelig process removes the nuclear fuel from the reactor pressure vessel and consequently removes most of the radioactivity from the reactor plant. Defueling is an operation routinely accomplished using established processes at shipyards used to perform reactor servicing work.

A disposal method for the defueled reactor compartments is needed when the cost of continued operation is not justified by the ships' military capability or when the ships are no longer needed. After a nuclear-powered ship no longer has sufficient military value to justify continuing to maintain the ship or the ship is no longer needed, the ship can be: (1) placed in protective storage for an extended period followed by permanent disposd or recychg; or (2) prepared for permanent disposd or recycling. The preferred alternative is land burial of the entire defueled reactor compartment at the Department of Energy Low Level Waste Burial Grounds at Hanford, Washington.

A ship can be placed in floating protective storage for an indefinite period. Nuclear-powered ships can dso be placed into storage for a long time without risk to the environment. The ship wodd be maintained in floating storage. About every 15 years each ship would have to be taken out of the water for an inspection and repainting of the hull to assure continued safe waterborne storage. However, this protective storage does not provide a permanent solution for disposal of the reactor compartments from these nuclear-powered ships. Thus, this alternative does not provide permanent disposal.

Before a ship is taken out of service, the spent fuel is removed from the reactor pressure vessel of the ship in a process called defueling. This defueling removes all of the fuel and most of the radioactivity from the reactor plant of the ships. The fuel removed from the decommissioned ships would be handed in the same manner as that removed from ships wtich are being refueled and returned to service. Unlike the low-level radioactive material in defueled reactor plants, the Nuclear Waste Poficy Act of 1982, as amended, requires disposd of spent fuel in a deep geological repository.

Prior to disposal, the reactor pressure vessel, radioactive piping systems, and the reactor compartment disposd package wodd be sealed. Thus, they act as a containment structure for the radioactive atoms and delay the time when any of the radioactive atoms inside wodd be avtiable for release to the environment as the metal corrodes. This is important because radioactivity "decays" away with time; that is, as time goes on radioactive atoms change into nonradioactive atoms. Since ra&oactivity decays away with time, the effect of a delay is that fewer radioactive atoms would be released to the environment. Over 99.9% of these atoms are an integral part of the metal and they are chemically just like ordinary iron, nickel, or other metal atoms. These radioactive atoms are only released from the metal as a result of the slow process of corrosion. The remaining O.1% -- which is corrosion and wear products -- decay away prior to penetration of the containment structures by corrosion.

The Navy makes shipments of naval spent fuel to INEL that are necessary to meet national security requirements to defuel or refuel nuclear powered submarines, surface warships, or naval prototype or training reactors, or to ensure examination of naval spent fuel from these sources. The Secretary of Defense, upon notice to the Governor of the State of Idaho, certifies the total number of such shipments of naval spent fuel required to be made through the year 2035. The Navy will not ship more than twenty four (24) shipments to INEL from the date of this Agreement through the end of 1995, no more than thirty six (36) shipments in 1996, and no more than twenty (20) shipments per year in calendar years 1997 through 2000. From calendar year 2001 through 2035, the Navy may ship a running average of no more than twenty (20) shipments per year to INEL. The total number of shipments of naval spent fuel to INEL through 2035 shall not exceed 575. Shipments of naval spent fuel to INEL through 2035 shall not exceed 55 metric tons of spent fuel.

The Hanford Site is used for disposal of radioactive waste from DOE operations. The pre-LOS ANGELES Class submarine reactor compartments are placed at the Hanford Site Low Level Burial Grounds for disposd, at the 218-E-12B burial ground in the 200 East area. The disposd of the reactor compartments from the cruisers, LOS ANGELES, and OHIO Class submarines wodd be consistent with the pre-LOS ANGELES Class submarine reactor compartment disposd program. The land required for the btid of approximately 100 reactor compartments from the cruisers, LOS ANGELES, and OHIO Class submarines wuold be approximately 4 hectares (10 acres) which is similar to the land area needs for the pre-LOS ANGELES Class submarine reactor compartments.

An estimated cost for land burial of the reactor compartments is $10.2 million for each LOS ANGELES Class submarine reactor compartment, $12.8 million for each 0HIO Class submarine reactor compartment, and $40 million for each cruiser reactor compartment. The estimated total Shipyard occupational exposure to prepare the reactor compartment disposd packages is 13 rem (approximately 0.005 additiond latent cancer fatalities) for each LOS ANGELES Class submarine package, 14 rem (approximately 0.006 addtiond latent cancer fatalities) for each 0~0 Class submarine package and 25 rem (approximately 0.01 additiond latent cancer fatalities) for each cruiser package.




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Page last modified: 07-07-2011 12:57:38 ZULU