Why the United States should redesign its nuclear submarines

On August 21, Iranian Defense Minister Hossein Dehghan announced that the country's navy would soon take delivery of the first boat in the Fateh class of intermediate-size, Iranian-built submarines. The Fateh-class submarines are not nuclear-powered, but Iran has expressed aspirations for a nuclear sub; in April 2013, Fereydoun Abbasi-Davani, who heads the country’s Atomic Energy Organization, said that Iran may need highly enriched uranium in the future to fuel small engines for submarines. These announcements raise concerns that Iran might construct a nuclear submarine as a “back door” for acquiring a nuclear bomb.

Because of a loophole in the Nuclear Non-Proliferation Treaty, military nuclear power reactors are exempt from the safeguards placed on civilian power reactors. The reactors in nuclear submarines often use uranium enriched to much higher levels than the uranium used in civilian power reactors; the American Ohio-class subs, regarded as the world’s best, use uranium enriched past 90 percent—about the same enrichment level as in nuclear weapons. Therefore, states such as Iran can claim that they have a legitimate need for highly enriched uranium (HEU) for naval reactors, and the uranium used by these reactors remains free from any safeguards systems. It would be easy for states to build a nuclear weapon with this HEU, or for states to retain a “crash” capability to go nuclear in a matter of months if prompted to do so by a deteriorating security situation.

The United States currently possesses meager grounds to protest foreign development of HEU-powered submarines because the American submarine fleet is also powered by HEU. The Obama administration has committed itself to countering nuclear proliferation, yet the Navy seems allergic to researching the use of low-enriched uranium (LEU) to power its submarines. The Obama administration must identify LEU naval reactor development as a priority for future submarine designs—particularly for the SSBN(X) design that is in development and meant to succeed the Ohio-class submarines once those age out of service. The United States could then invest in LEU technology and redefine the gold standard for submarines with a fleet of LEU-powered boats. American adoption of LEU technology would deprive Iran and other states of a seemingly legitimate pretext to develop an effective crash nuclear capability.

The US Navy must cooperate if the United States hopes to counter the proliferation of HEU-powered submarines, but the historical record suggests that the Navy perceives little incentive to switch to LEU reactors. A 1995 report prepared by the director of Naval Nuclear Propulsion identified several problems with using LEU as a power source, including the added bulk of the reactor compartment, the need for frequent refueling of the reactor, and increased operational complexity.

However, in 2001, Chinese researcher Chunyan Ma and Princeton University’s Frank von Hippel suggested in an article in The Nonproliferation Review that the Navy develop an LEU reactor based on designs for French LEU-powered Rubis-class submarines. A Rubis-type reactor would be more compact than the 1995 Navy report anticipated, and with further research it could outperform the current Navy expectations. In July 2012, the House Armed Services Committee instructed the Office of Naval Reactors to update the 1995 report in light of advances in LEU naval reactor technology. The update was due on March 1, 2013, but it appears that provisions for preparing the report were dropped during the reconciliation between the House and Senate versions of the National Defense Authorization Act—a possibility that only underscores the necessity of explicit executive action.

The Obama administration should direct the Defense Department to consider LEU-fueled reactors in the design schematics for the submarines that will replace the current Ohio-class boats, and it should make funding available for LEU research. Failure to do so will represent a missed opportunity for a major positive step in support of nonproliferation. If the SSBN(X) boats run on HEU reactors, then the United States will lack credibility for the next 40 years—the service life of the SSBN(X)—when it asks other states to curb HEU-fueled nuclear submarine acquisition, and proliferating states will have 40 years of excuses to manufacture weapons-grade uranium.