Cyclotron and linac production of AC-225

Full text: Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. The reduction of radium by photonuclear transmutation by bombarding Ra-226 with high-energy photons from a medical linac has been investigated. A linac dose of 2800 Gy produced about 23 mCi of Ra-225, which decays to Ac-225, and can then be used for 'Targeted Alpha Therapy' (TAT) of cancer. This result, while consistent with theoretical calculations, is far too low to be of practical use. The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. This paper investigates the production of Ac-225 in commercial quantities, which could potentially reduce obsolete radioactive material, and displace the need for expensive importation of Ac-225 from the USA in the years ahead. Scaled up production of Ac-225 could be achieved by the use of a high current cyclotron or high-power linac Production specifications are determined for a linear accelerator in terms of current, pulse length and frequency. Yields are compared with those calculated for the Australian National Cyclotron in Sydney