Tc-99 in stars, reactors, and nuclear medicine

The roles of Tc-99g in stars and in nuclear fission reactors and that of Tc-99m in nuclear medicine that were studied using neutrons provided from accelerators are reported. In addition to the critical role of Tc-99g in stars, we also describe the roles of related light nuclei such as O-16, and experimental studies on keV-neutron capture cross sections of these light nuclei that were performed using keV neutrons provided from a 3.2-MV Pelletron accelerator are reported. The keV-neutron capture cross section of Tc-99g, that is important in studies on the nucleosynthesis of Tc-99 in stars and on the nuclear transmutation of long-lived nuclear wastes produced in fission reactors, were measured. The cross sections of both light nuclei and Tc-99g were measured using a neutron time-of-flight method with a ns-pulsed neutron source from the Li-7(p,n)Be-7 reaction and with an anti-Compton gamma-ray NaI(Tl) spectrometer. The measurements reported here were compared with the values of recent worldwide evaluated nuclear data libraries. We proposed a method of producing Tc-99m from the Mo-100(n,2n)Mo-99 reaction, and performed a Tc-99m production experiment using a Mo-nat sample and MeV neutrons from the C-nat(d,n) reaction by 40 MeV deuterons at a cyclotron. Calculations for the Tc-99m production with an enriched Mo-100 sample were also performed, and calculated results were compared with the experimental results. Moreover, the thermoseparation of Tc-99m from Mo-99 was discussed. As a result, it was shown that Tc-99m prepared by the thermoseparation using Mo-99 produced by the Mo-100(n,2n)Mo-99 reaction can be a promising substitute for the fission product Mo-99.