U. S. Highly Enriched Uranium: Mitigating the Risk


By: Greg Terryn

For terrorists seeking to develop a nuclear weapon or improvised nuclear device, the most challenging obstacle is the acquisition of enriched nuclear material. This makes the protection of fissile materials, such as highly-enriched uranium (HEU) and plutonium, a national security priority. In response to this threat, the U.S.’ Defense Nuclear Nonproliferation program is tasked with securing both domestic and international stockpiles of these materials (and deserves more funding for its efforts).  But after several security failures, there are concerns about whether the United States’ stockpile of HEU is secure.

US Stockpile of HEU

As of 2013, the United States has a stockpile of 686.6 metric tons of highly enriched uranium: uranium with a 20% or higher concentration of U-235 isotope. The U.S. uses its HEU primarily for nuclear weapons and the fueling of naval reactors; only a small percentage of the stockpile is used for civilian power reactors, which tend to run on low-enriched uranium. In 1992, the U.S. instituted a freeze on its HEU production and a majority of the remaining material, some 400 metric tons, is stored at the Y-12 National Security Complex in Tennessee.

Security Concerns:  Octogenarian Nun and Air-dropped Porn

The track record for HEU security within the United States is fraught with reasons for concern. In July 2012, three peace-activists, led by an 82-year old nun armed with a pair of wire-cutters, snuck past fences and security sensors to breach the most secure area of the Y-12 National Security Complex. The group painted anti-war slogans on the HEU storage facility and waited several hours before finally being apprehended by a lone guard. This was not a tactical operation executed by an elite military unit, but three aged and unarmed protestors with pacifist intentions.

Security forces at Y-12 fair just as poorly when the opposition is armed and well-trained. From 2003-2007, Y-12 guards were 0-3 in “force-on-force exercises,” allowing the mock terrorists to acquire the HEU each time.  Y-12 has also been vulnerable to aerial threats, including a bizarre 1996 incident in which a man rented a small plane and flew into restricted air space to disperse lewd photos of his ex-girlfriend across the premises.

Lax security standards for the HEU stockpile pose an incalculable risk to national security, especially considering the material would be loose on American soil. With approximately 25 kilograms of HEU, a terrorist organization could make a crude nuclear explosive with the potential to match the devastating nuclear explosions at Hiroshima and Nagasaki. Even if a terrorist group could not acquire the HEU, detonating conventional explosives at the Y-12 nuclear facility would scatter fissile material into the air, creating a radioactive hazard with long-term effects on the surrounding area.

Reducing Reliance on HEU: Downblending & LEU Naval Reactors

While increasing security capabilities at these facilities can mitigate some risk, the sure-fire way to eliminate the proliferation and security risk posed by HEU is to reduce and eliminate the material. For instance, weapons grade (93% U-235) and highly enriched uranium (enriched to more than 20% U-235) could be converted to low-enriched uranium (3-5% U-235) to be used for commercial nuclear fuel through a process known as downblending, which leaves the uranium unsuitable for weapons activity. The U.S. has downblended large quantities of HEU, including 500 metric tons of Russian weapons-grade uranium (enough for 20,000 nuclear weapons) through the Megatons-to-Megawatts program.

Though downblending is useful for converting excess HEU into nuclear fuel, the US currently maintains a stockpile for use in nuclear weapons and naval reactors. Though low-enriched uranium (LEU) is insufficient for nuclear weapons maintenance, studies have been conducted to explore the potential of LEU use in U.S. naval reactors. A recent Federation of American Scientists-convened task force explored the potential for this technological breakthrough, concurring with a 2014 Office of Naval Reactors report that there is potential for a LEU naval reactor, although success is not assured.  Both reports express concern over the potential for increased maintenance and development costs, operational restrictions posed by a mid-life refueling, and reduced performance capabilities as a result of the switch from HEU to LEU fueling. There is, however, hope that new designs and technological breakthroughs could mitigate these concerns and create an effective LEU naval reactor.

Development of an effective LEU reactor is expected to take 10-15 years. The taskforce recommends the United States initiate a research and development program on advanced low-enriched uranium fuel by 2017 in order to have a potential LEU reactor prepared by 2032 when construction is scheduled to begin on the new Virginia-class submarines. If the process is delayed, the hope is that a potential LEU reactor could be designed by 2040 to serve in the replacement to the Ford-class Aircraft Carriers.

Any new reactor that is designed would need to pass rigorous testing and meet the Navy’s performance standards before being implemented. Beginning research on LEU fuel by 2017 would give the US Navy and Department of Energy ample time to thoroughly explore potential for an effective naval reactor without the associated proliferation and security risks of using HEU. France and China currently use LEU reactors in their navy, and Russia has designed a reactor to be used in new icebreaking ships. Developing a LEU reactor would push both the US and Britain, who receives its nuclear fuel and submarine reactor technology from the US, away from dependence on HEU and reduce the global proliferation and security risks associated with the enriched materials.

Jumpstarting a research program now could lead to considerable downblending of HEU in the future and decrease nuclear proliferation and terrorism risks. While success in developing a LEU reactor is not assured, funding research on this technology is a smart, easy first step towards modernizing our naval forces and improving national security.