When It Comes to Fissile Material, More Is Not Better

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The March/April issue of the Bulletin of Atomic Scientists has an article (unfortunately behind a paywall) about the enormous stockpiles of plutonium and highly enriched uranium (HEU) the United States still retains for weapons purposes, co-authored by GSP Program Director Lisbeth Gronlund and myself. The article is based on chapter 6 of UCS’s recent report, Making Smart Security Choices, and concludes that the United States should immediately declare much more of this material excess and dispose of it in ways that minimize the risk that it could be stolen by terrorists and used to make a nuclear weapon.

radiation symbol heapAfter disposing of the material it has already declared excess to military requirements, the United States will still retain enough plutonium for around 10,000 nuclear weapons, and enough highly enriched uranium for 10,000 to 16,000 weapons.  (All current U.S. nuclear weapons contain both plutonium and uranium, so these numbers are not cumulative.)  The U.S. arsenal, while still much larger than needed, has now fallen to somewhat fewer than 5,000 deployed and reserve weapons. The United States should declare excess all fissile material above the amount needed for an arsenal of this size.  This would mean declaring excess an additional 18 metric tons of plutonium and 135 metric tons of HEU. Although a small step, this would be consistent with President Obama’s pledge to move toward a world without nuclear weapons. To reduce the risk that terrorists will acquire nuclear materials, the United States should dispose of its excess plutonium directly, rather than by turning it into mixed-oxide (MOX) fuel to be used in commercial nuclear reactors. Before it is irradiated, MOX fuel does not contain the highly radioactive elements that make the spent fuel dangerous to handle, and the plutonium in the fuel can be separated by a straightforward chemical process, increasing security risks. On MOX, at least, the most recent federal budget request is a step in the right direction, placing the program into cold standby while evaluating alternative plutonium disposal methods.

Declaring additional weapons-usable fissile material excess and moving to dispose of it more quickly would benefit U.S. security by reducing the amount of this material that could fall into terrorist hands. It would have the added benefit of demonstrating that the Obama administration is still committed to its stated goal of reducing the number and role of U.S. nuclear weapons. In the case of fissile material, more is not better. Less—and quickly—would be.


Posted in: Nuclear Terrorism, Nuclear Weapons Tags: , , , , , , ,

About the author: Ms. MacDonald received her MA in International Relations and Comparative Politics from Cornell University in 2009, specializing in China. Before coming to UCS in 2011 she worked at the MIT International Science and Technology Initiatives (MISTI) program, and was an instructor at Endicott College teaching courses on international relations. Areas of expertise: Nuclear weapons complex, China

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  • Denis

    Did you guys miss the news about Russia reverting back to its empire building project?

    Do you think Russia will agree to *reduce* its nuclear arsenal?

    If anything, I expect it to build more of them, since conventionally Russian armed forces are no match for US.

    Creating more weapon-grade Pu, if needed, will be *extremely* expensive. And we can’t absolutely rule out that we won’t need to do that – future is not predictable.

    Therefore getting rid of existing Pu created at enormous expense strikes me as stupid.

  • Eryn MacDonald


    Thanks for your comment. I understand your concern about the developments in Ukraine but, disturbing as that situation is, our argument stands. The United States currently has enough fissile material to build around 10,000 nuclear weapons. Russia has already reduced its arsenal below the level of 1,550 deployed strategic nuclear weapons agreed upon in the New START treaty, while the United States is still moving toward that level (the deadline for reaching it is 2018).

    In our article, we argue that the United States should dispose of all fissile material in excess of that needed for 5,000 weapons. Whatever you think of the situation in Ukraine today, this is far more than the United States needs to respond to any contingency, regardless of the number of weapons Russia has.

    Retaining huge amounts of excess fissile material does nothing to improve U.S. national security vis a vis Russia, but does leave this material more vulnerable to be stolen and used by terrorists. This is the threat that we need to address, and disposing of excess weapons plutonium and highly enriched uranium is one of the easiest ways to reduce this threat.