Shua Sanchez
Program on Science and Global Security, Princeton

Plutonium Pit Aging

Zoom link: https://mit.zoom.us/j/92547023849

Abstract: In a modern two-stage thermonuclear warhead, the plutonium shell (or pit) at the core of the weapon’s primary stage must undergo nuclear fission with a large enough yield to drive a fusion reaction in the secondary stage. Changes in plutonium bulk properties over time (an effect called “aging”) can potentially degrade the performance of the primary and the yield of the warhead overall. These changes can stem from the spontaneous radioactive decay of plutonium nuclei, creating several kinds of lattice defects with distinct effects on mechanical properties. Studies over the past two decades have suggested pits remain viable for at least 80-100 years despite plutonium aging effects. However, the US National Nuclear Security Association has recently pushed for renewed plutonium pit production, motivated in part by a suggestion that current pits may be degrading faster than expected. This presentation will offer a review of aging studies and a technical analysis of the new claims about the speed of plutonium aging, highlighting possible limitations of the experimental design underlying them. It will suggest a need for more research on whether plutonium pits are aging more quickly or slowly than expected to allow a better informed policy debate on plutonium pit production.

Bio: Shua Sanchez is a materials physicist, a research collaborator with the Program on Science and Global Security, and a 2025 Next-Generation Fellow with the Physicist Coalition for Nuclear Threat Reduction. His research involves a critical review of the scientific literature on plutonium aging effects used to justify U.S. plans for the production of new plutonium cores (pits) for existing and new nuclear weapons. From 2021 to 2025 he was a National Science Foundation Postdoctoral Fellow at MIT pursuing experimental condensed matter physics for energy-efficient electronics applications. He holds a physics PhD from the University of Washington (2021) and a B.S. in physics from the University of Wisconsin. A longtime activist and union organizer, Shua was an elected member of the executive board of the University of Washington’s graduate student union, UAW 4121, and has worked on Democratic political campaigns across the country.