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Nuclear Archaeology: Verifying Declarations of Fissile-material Production

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Controlling the production of fissile material is an essential element of nonproliferation policy. Similarly, accounting for the past production of fissile material should be an important component of nuclear disarmament. This paper describes two promising techniques that make use of physical evidence at reactors and enrichment facilities to verify the past production of plutonium and highly enriched uranium. In the first technique, the concentrations of long-lived radionuclides in permanent components of the reactor core are used to estimate the neutron fluence in various regions of the reactor, and thereby verify declarations of plutonium production in the reactor. In the second technique, the ratio of the concentration of U-235 to that of U-234 in the tails is used to determine whether a given container of tails was used in the production of lowenriched uranium, which is suitable for reactor fuel, or highly enriched uranium, which can be used in nuclear weapons. Both techniques belong to the new field of “nuclear archaeology,” in which we attempt to document past nuclear weapons activities and thereby lay a firm foundation of verifiable nuclear disarmament.

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