Average neutron cross sections of Tc-99

Tc-99 has been the subject of several experimental programs at the JRC-Geel since the late 1990's. This work presents new transmission data measured at the GELINA facility with the time-of-flight technique, whose simultaneous analysis with past transmission experiments provided a revised set of resonance parameters up to 5 keV. An iterative analysis between the resonance and 'continuum' energy ranges leads to average resonance parameters [S₀ = 0.51(3), <Γ_γ0 > = 137(7) meV, D₀ = 12.8(2) eV] and theoretical average capture cross sections consistent with those reported in the literature. At E = 30 keV, we obtain a capture cross section of 1076(45) mb and a Maxwellian-averaged cross section (MACS) of 1016(43) mb. The agreement with the recommended MACS value of 933(47) mb remains within the quoted uncertainties. This result demonstrates the performances of transmission experiments to provide reliable theoretical capture cross sections for long-lived fission products in the energy range of interest for s-process nucleosynthesis calculations. (author)