Cyclic Activation with a Californium-252 Source

A 1-mg ²⁵² Cf neutron source is employed for neutron activation analysis studies on short half-life isotopes utilizing a cyclic irradiation-count sequence. A pneumatic, rapid-transfer system is used to transport samples from the irradiation position near a neutron source to the counting position adjacent to a gamma-ray spectrometer. Improved sensitivities are achieved for shortlived isotopes by selecting the optimal or near optimal cyclic policies. Interference-free sensitivities for several isotopes of possible interest are determined and compared to sensitivities achieved by conventional, noncyclic neutron activation analysis. The enhancement of the shortlived components is demonstrated for complex photospectra. Finally, the usefulness of a cyclic activation-counting procedure mth the ²⁵²Cf source is demonstrated for the assay of enriched uranium suggesting potential special nuclear materials safeguards applications.