Nuclear data for reactor production of Ba and Ba.

The newest radioisotope for brachytherapy treatment of prostate cancer is Cs (t = 9.69 d, 100% EC). Generated via electron capture decay of Ba (t = 11.6 d, 100% EC), Cs has been used in brachytherapy for prostate cancer since 2004. The Ba parent is produced through neutron capture of enriched Ba in a nuclear reactor. For large-scale production of Ba, an accurate knowledge of production and burnup cross sections of Ba are essential. In this paper, we report two group cross sections (thermal and resonance integrals) for Ba and Ba and a new measure of the half-life of Ba. Targets consisting of milligram quantities of enriched Ba (∼35%) were irradiated in Oak Ridge National Laboratory's High Flux Isotope Reactor at thermal and resonance neutron fluxes of (1.9-2.1) × 10 and (5.8-7.0) × 10 neutrons·cm s, respectively, for durations ranging from 3 to 26 days. In addition, cadmium covered samples of Ba were irradiated for 1 hour at 12.6% full reactor power (10.7 MW). The yield of Ba approaches a saturation value of ∼60 GBq (∼1.6 Ci) per mg of Ba for 20 days irradiation at a thermal neutron flux of 1.8 × 10 n·s·cm, with a thermal/epithermal ratio of ∼30. Under the above experimental conditions, the two group cross sections of Ba are 6.9 ± 0.5 b (thermal, σ) and 173 ± 7 b (resonance, I). These values represent the sum of cross sections to metastable and ground states of Ba. For Ba, the empirically measured thermal cross section is 200 ± 50 b assuming an I/σ of 10. This cross section is reported for the first time. Further, the half-life of Ba was remeasured to be 11.657 ± 0.008 d. Lastly, this study also resulted in the co-production of Ba (t = 10.52 y, 100% EC). The experimental yield of Ba is ∼370 MBq (∼10 mCi) per mg of Ba (thin target) for one cycle irradiation in the High Flux Isotope Reactor, and measured two-group Ba cross sections are 7.2 ± 0.2 b and 39.9 ± 1.3 b. These values also represent the sum of cross sections to metastable and ground states of Ba.