Data presented permit estimation of the available neutron fluxes and shielding requirements of irradiation devices that use a 252Cf neutron source. A practical irradiation device, suitable for neutron activation analysis and capable of producing a thermal flux of ∼0.02 cm−2 per source neutron, can be constructed by placing the source at the center of an equilateral cylinder or cube of high-density polyethylene having diameter or width of ∼1 ft. Biological shielding requirements vary from ∼2 ft of normal concrete or water for a source of 1 mg 252Cf to ∼5 ft of dense, hydrogenous concrete for a source of 1 g 252Cf.