The Non Destructive Assay of Special Nuclear Materials in Different Physical Forms

Passive neutron correlation counting is a non destructive assay technique extensively used to quantify Pu and a few other spontaneously fissile materials. In applying the method it is often assumed that the nuclear decay parameters are unaffected by the physical form of the material. Recently it has been suggested, based on predictions of the Drude-Debye model for the behavior of electrons in metals, that the half life of transuranic nuclides in metallic environments can be shortened dramatically compared to nuclei in free space or atoms in an insulator. In this work we compare the specific correlated neutron outputs for Pu items in the form of dioxide (insulator) and the form of a metallic alloy with Ga. Differences were within the limits of these experiments. An upper bound is set on the magnitude of the difference in the decay properties in the two environments.