United States Navy submarines and aircraft carriers are powered by reactors that use highly enriched uranium in order to meet demanding performance requirements. However, consistent with its national security requirements and in recognition of the nonproliferation benefits to minimizing the use of highly enriched uranium globally, the United States values investigations into the viability of using low-enriched uranium in its naval reactors.
The United States has studied the feasibility of using low-enriched uranium in naval reactors and documented the conclusions from these studies in public reports to Congress that were issued in 1995 and 2014. These studies concluded that existing naval reactor designs are not conducive to using low enriched uranium due to the significant impact this would have on reactor lifetime, size, and ship costs. However, the 2014 report to Congress concluded that the potential exists to develop an advanced fuel system that could increase uranium loading beyond what is practical today while meeting the rigorous performance requirements for naval reactors. Such an advanced fuel system might allow using low enriched uranium fuel with less impact on reactor lifetime, size, and ship costs.
Following the 2014 report, Congress directed the Navy and Department of Energy to consider initiating a program of work to develop low enriched uranium fuel for use in naval reactors. In response, Naval Reactors is developing a conceptual research and development plan for an advanced fuel system that could enable use of low enriched uranium in naval reactors.
Barack Obama, Fact Sheet: Feasibility of Low Enriched Uranium Fuel in Naval Reactor Plants Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/318312