REPORT ON IN NAVAL NUCLEAR JUNE, 1995

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c. LEU IN CURRENT DESIGN SHIPS:
1. Submarines: For a modern attack submarine with a 33-year ship life and a life-of-the-ship core,
the reduction in fissile content in switching from REU to LEU has the effect of reducing core endurance by
a factor offour. to about seven-and-a-halfyears, or about one-fourth the life of the ship.
The last ship ofUSS omo (SSBN726) Class of strategic deterrent submarines will be delivered, with its
initial REU core, in 1996. The cores in these ships, designed with late 1970's technology, v.-i1I operate for
over 20 years. The liEU refueling cores to support the one required refueling of these ships v.-i1I be
procured before an LEU manufacturing capability would exist, and therefore the SSBN726 Class ships do
not figure directly into this REU/LEU assessment.
Assuming a strategic force will continue to be maintained, a new class of SSBNs will eventually have to be
built to replace the SSBN726 Class. By the time this new class of ships would be designed, a 45-year
REU core should be feasible (see CVN discussion below). For the purposes of this report, the baseline
assumption for a new class SSBN will be a ship of about the same size and propulsion power as SSBN726,
with a ship life of 45 years and a life-of-the-ship REU core. The LEU version of this core would have an
endurance of about ten-and-a-halfyears, or about one-fourth the ship life.
TABLE 2
ComQarison of LEU and REU Core Lifetimes in Submarines
(SSN and SSBW
REU REU LEU LEU
SSN SSBN SSN SSBN
Core Lifetime, years 33 45 7.5 10.5
Number of Cores in Ship Life 1 1 4 4
Number of Refueling 0 0 3 3
Overhauls in Ship Life
2. Aircraft Carriers: The design of the REU cores used in the USS NII\mZ (CVN68) Class
aircraft carriers is based on early 1970's technology, and has mechanical features which facilitate reactor
servicing but which make less than fully efficient use of the active core volume. This core operates for
over 20 years, so, like the SSBN726 Class, one refueling is required during the approximately 45 year life
of the ship.
The current CVN68 Class reactor vessel is judged to be able to accommodate all the fissile fue4 control
poison, cladding and support structure required for a life-of-the-ship REU core. The limiting technical
consideration is corrosion of the cladding. Advanced cladding materials are in development and testing,
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