New Encapsulation Techniques for the Fabrication of Californium-252 Neutron Sources

New ²⁵²Cf encapsulation techniques have been developed which offer possibilities of variation in source strength and geometry. These techniques involve the concentration of ²⁵²Cf by extraction into an organic phase, followed by calcination to the oxide, and either fusion into a silica sphere or compression into an aluminum container. To date, sources containing from 8 to 100 µg of ²⁵²Cf have been prepared by fusion of the oxide into silica spheres about 1.6 mm in diameter. Sources containing up to 5 mg of ²⁵²Cf have been prepared by compression of mixed californium and aluminum oxides in aluminum powder to form aluminum cylinders 9.5 mm high and 6.5 mm in diameter. These new techniques make a significant contribution toward the technology necessary for the fabrication of ²⁵²Cf neutron sources, which are finding useful applications in many fields, including cancer therapy, mineral exploration, oil-well logging, on-site production of short-lived isotopes, and on-line analysis of flowing process streams.