In this paper we discuss our experimental work in photoproducing two medically-useful radioisotopes ( 68 Zn(c,p) 67 Cu and 48 Ca(c,n) 47 Ca ? 47 Sc) using an electron linear accelerator. We further address the issues of production and separation of medical isotopes arising from photoneutron (c,n) and photoproton (c,p) reactions. While (c,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both nuclides are identical. Although the yields of (c,p) reactions are typically lower than for (c,n), these proton-rich isotopes have the advantage that target and product nuclides belong to different chemical species allowing for more straightforward chemical separation. We conclude the paper by touching upon the dire necessity of experimentally revisiting a broad swath of photonuclear reactions in the 10-to 50-MeV regime. The very paucity of empirical cross-sectional data makes it altogether impossible to realistically predict accelerator-based photoproduction of many promising radiopharmaceuticals.

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In this work we have studied the feasibility of photonuclear production of (47)Sc from (48)Ti via (48)Ti(γ,p)(47)Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. (47)Sc production rate dependence on electron beam energy was found and (47)Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of (47)Sc. Irradiating enriched (48)Ti targets with a 22MeV 1mA beam will result in hundreds of MBq/g activity of (47)Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of (47)Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the (48)Ti(γ,np)(46)Sc reaction threshold, (46)Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22MeV electron beam incident on the tungsten converter. Measured (47)Sc activities were found to be in very good agreement with the predictions.

In this work we have studied the feasibility of photonuclear production of (47)Ca from (48)Ca for (47)Ca/(47)Sc generators. Photon flux distribution for electron beams of different energies incident on a tungsten converter was calculated using the MCNPX radiation transport code. The (47)Ca production rate dependence on electron beam energy was found and (47)Ca/(47)Sc yields were estimated for a 40MeV electron beam. It was shown that irradiating enriched targets with a 40MeV, 1mA beam will result in tens of MBq g(-1) (few mCi g(-1)) activity of (47)Sc. The results of the simulations were benchmarked by irradiating 22.5g of CaCl2 powder with a 39MeV electron beam incident on a tungsten converter. Measured (47)Ca/(47)Sc activities were found to be in very good agreement with the predictions.