GAO's analysis shows that conventional and nuclear carriers both have been effective in fulfilling U.S. forward presence, crisis response, and war-fighting requirements and share many characteristics and capabilities. Conventionally and nuclear-powered carriers both have the same standard air wing and train to the same mission requirements. Each type of carrier offers certain advantages. For example, conventionally powered carriers spend less time in extended maintenance, and as a result, they can provide more forward presence coverage. By the same token, nuclear carriers can store larger quantities of aviation fuel and munitions and, as a result, are less dependent upon at-sea replenishment. There was little difference in the operational effectiveness of nuclear and conventional carriers in the Persian Gulf War.
Investment, operating and support, and inactivation and disposal costs are greater for nuclear-powered carriers than conventionally powered carriers. GAO's analysis, based on an analysis of historical and projected costs, shows that life-cycle costs for conventionally powered and nuclear-powered carriers (for a notional 50-year service life) are estimated at $14.1 billion and $22.2 billion (in fiscal year 1997 dollars), respectively.
The United States maintains a continuous presence in the Pacific region by homeporting a conventionally powered carrier in Japan. If the U.S. Navy transitions to an all nuclear carrier force, it would need to homeport a nuclear-powered carrier there to maintain the current level of worldwide overseas presence with a 12-carrier force. The homeporting of a nuclear-powered carrier in Japan could face several difficult challenges, and be a costly undertaking, because of the need for nuclear-capable maintenance and other support facilities, infrastructure improvements, and additional personnel. The United States would need a larger carrier force if it wanted to maintain a similar level of presence in the Pacific region with nuclear-carriers homeported in the United States.
http://www.gao.gov/archive/1998/ns98001.pdf