The head of the National Nuclear Security Administration’s naval reactors program suggested Wednesday the use of highly enriched uranium for naval propulsion offers a significant advantage over conversion to low-enriched uranium – indicating the U.S. Navy’s longstanding preference for HEU is unlikely to change.
Adm. James Caldwell Jr., the NNSA’s deputy administrator for naval reactors, said at a Senate Appropriations energy and water subcommittee hearing that “success would not be guaranteed” in an LEU-based system. “It’s quite a leap to go forward,” he said, because it would involve “essentially adding less energy to the core.”
Advocates for global minimization of weapon-grade uranium have pushed the Navy to consider the feasibility of converting naval reactors to LEU. The nongovernmental Fissile Materials Working Group, for one, released a report in 2015 recommending research and development toward that goal.
The Nuclear Threat Initiative last year made similar recommendations, while acknowledging that conversion of naval reactors would require development of new reactors and new fuels. Still, NTI pointed to the French navy’s conversion of its fleet to LEU power as an example of the possibility.
The U.S. Navy, meanwhile, has previously concluded in reports to Congress that adopting LEU technology would create disadvantages for its fleet, which includes close to 100 nuclear-powered ships.
Caldwell said during Wednesday’s hearing on the NNSA’s fiscal 2018 budget plan that the result of such a conversion would be “less endurance, less energy to use for anything on the ship, you would have to probably refuel it more frequently, you would take it offline . . . you might actually have to build more submarines so that you could maintain the required presence that you need forward.”
HEU cores in naval reactors last for the life of the ship, he noted, adding that the HEU cores of the Navy’s new Columbia-class ballistic missile submarines will have 42-year lives. The NNSA in 2014 reported to Congress that LEU would reduce core life by a factor of three to four, which would require ships to be refueled two to three times instead of once or not at all.
Development of LEU cores would take roughly $1 billion over 10 to 15 years, Caldwell said, and would also require development of an advanced fuel system.
Those numbers are based on a report the NNSA submitted to Congress last year on the cost and timeline of developing an LEU production capability for naval reactors. That report also noted that the naval reactors program has operated over 30 different reactor designs in over 20 plant types.
The Navy plans to build 12 Columbia-class submarines that will enter into service in the 2030s as the sea-based leg of the U.S. nuclear deterrent. The Navy said it needs 10 SSBNs at sea to meet deterrence requirements, and is procuring 12 to account for midlife overhauls and maintenance.
Some analysts, however, say a total of eight operational submarines is sufficient. The Congressional Budget Office in 2013 explored the option of reducing the SSBN force to eight to cut costs and said that this “would still provide a robust strategic deterrent at sea.”
The White House has requested $13.9 billion in funding for the NNSA in fiscal 2018, of which $1.5 billion would go toward naval nuclear propulsion work – 4.2 percent above the currently enacted $1.4 billion. This would fund the development of reactor technology and operation of reactors in nuclear-powered submarines and aircraft carriers, among other related work.
