Cross sections for (223,)(225)Ra, (225)Ac and (227)Th production by the proton bombardment of natural thorium targets were measured at proton energies below 200 MeV. Our measurements are in good agreement with previously published data and offer a complete excitation function for (223,)(225)Ra in the energy range above 90 MeV. Comparison of theoretical predictions with the experimental data shows reasonable-to-good agreement. Results indicate that accelerator-based production of (225)Ac and (223)Ra below 200 MeV is a viable production method.

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Accelerator production of 225 Ac addresses the global supply deficiency currently inhibiting clinical trials from establishing 225 Ac's therapeutic utility, provided that the accelerator product is of sufficient radionuclidic purity for patient use. Two proton activation experiments utilizing the stacked foil technique between 40 and 200 MeV were employed to study the likely co-formation of radionuclides expected to be especially challenging to separate from 225 Ac. Foils were assayed by nondestructive -spectroscopy and by -spectroscopy of chemically processed target material. Nuclear formation cross sections for the radionuclides 226 Ac and 227 Ac as well as lower lanthanide radioisotopes 139 Ce, 141 Ce, 143 Ce, and 140 La whose elemental ionic radii closely match that of actinium were measured and are reported. The predictions of the latest MCNP6 event generators are compared with measured data, as they permit estimation of the formation rates of other radionuclides whose decay emissions are not clearly discerned in the complex spectra collected from 232 Th(p,x) fission product mixtures.

Nuclear formation cross sections are reported for 65 nuclides produced from 800-MeV proton irradiation of thorium foils. These data are useful as benchmarks for computational predictions in the ongoing process of theoretical code development and also to the design of spallation-based radioisotope production currently being considered for multiple radiotherapeutic pharmaceutical agents. Measured data are compared with the predictions of three MCNP6 event generators and used to evaluate the potential for 800-MeV productions of radioisotopes of interest for medical radiotherapy. In only a few instances code predictions are discrepant from measured values by more than a factor of two, demonstrating satisfactory predictive power across a large mass range. Similarly, agreement between measurements presented here and those previously reported is good, lending credibility to predictions of target yields and radioimpurities for high-energy accelerator-produced radionuclides. 25.40.Sc, 87.56.bd PACS number(s):

We report separation data indicating that 99Mo can be separated from a vast excess of either uranyl sulfate or uranyl nitrate in irradiated dilute acid solutions. These results suggest that, if medical isotope 99Mo is produced during fission of high concentrations of low enriched uranium sulfate solution fuel, it is feasible to both recover >90% of the 99Mo for further purification and the uranium for recycle.