Reactor production of promethium-147

In this paper, we describe the ¹⁴⁷Pm production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched ¹⁴⁶Nd oxide irradiated at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory for durations ranging from 24 to 180 h. A comparison between theoretical and experimental data are also presented, and attempts were made to empirically evaluate the neutron capture cross-sections of 41.3-d ^148mPm and 5.4-d ^148gPm. For a one-cycle irradiation (~24 days), ¹⁴⁷Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days after the end of bombardment. Because of large neutron capture cross-sections of ¹⁴⁷Pm, the yield of ¹⁴⁷Pm does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for ¹⁴⁶Nd at 1.48 ± 0.05 b and 2.56 ± 0.25 b, respectively, were consistent with the reported values. The effective neutron capture cross-section of ¹⁴⁷Pm to ^148mPm was 53.3 ± 2.7 b-a factor of 2 lower than the 98.7 ± 6.5 b calculated from reported cross-sections. The measured σ_eff to the ground state (5.37-d ^148gPm) was 82.0 ± 4.1 b; ~34% lower than the value of 139 ± 10 b calculated from reported cross-sections. In this work, we also describe the development of a chemical process based on extraction and ion-exchange chromatography for separation of ¹⁴⁷Pm from milligram quantities of ¹⁴⁶Nd and other impurities. Sequential separation of Pm from the Nd target and from other radioisotopic impurities (¹⁵³Gd and ^154&155Eu, ¹⁹²Ir, and ⁶⁰Co) was achieved using a LN extraction resin in HCl media followed by further purification of Pm from ⁶⁰Co and ¹⁹²Ir using a low cross-linking cation exchange resin. Based on these data, we estimated that two rounds of purification under our experimental conditions can provide a mass separation factor of >10⁴ between Pm and Nd. Our data indicate that curie quantities of ¹⁴⁷Pm with suitable chemical and radioisotopic purity for applications in beta voltaic batteries can be produced by irradiating gram quantities of highly enriched ¹⁴⁶Nd in the flux trap of HFIR for one cycle.