A Versatile Cobalt-60 Sample Irradiation Unit Some Design Features and Dose Measurements

The design of a 5000 curie double-well 60 Co irradiation unit is described. The 5 in. diameter × 8 in. high irradiation volume enclosed by the cylindrical source has access tubes for electrical and fluid connections to the sample during irradiation. The upper lead shield and the source are motor-driven. Operation is either by manual or fully automatic control. Dose measurements have been made with an aluminium absorbed dose calorimeter and with the ferrous-ferric system. They give 7·80±0·12×10 5 rad/hr in water (December, 1961) for the dose rate at the centre of the irradiation volume. The spatial dose distribution within the irradiation chamber has been mapped using a Plexiglas (polymethyl-methacrylate) dosemeter. Results of calibration of the radiation-induced optical absorption at 370 m μ against the ferrous-ferric system showed that the plastic dosemeter was linear with dose of 60 Co γ -rays up to 1·2×10 6 rads.