Teletherapy sources with imported and indigenous Co activity

Board of Radiation and Isotope Technology, a unit of the Department of Atomic Energy, fabricates and supplies radioactive sources for medical, industrial, agriculture and research applications. High specific activity cobalt-60, required for teletherapy is normally imported. There was a proposal for manufacturing high specific activity sources indigenously. A study was carried out to observe the feasibility of mixing imported and indigenous cobalt-60 pellets to fabricate teletherapy source capsules. The specific activity of imported pellets is more than 300 Ci/g, whereas that of indigenous pellets obtained from Indian power reactors is 140 Ci/g. The radiation output from a capsule for different combinations of specific activity was evaluated. Losses due to self-absorption were accounted in the evaluations. In another study, the optimized lengths of the capsule for an output of 200 RMM and the additional activity to be added to compensate losses due to self-absorption were also estimated for different specific activity pellets. Sources fabricated on the basis of this study showed a good agreement with the estimations. Source capsules with a combination of different specific activities are yet to be fabricated.