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tokens: uranium, in the very metal-poor star BPS CS31082-001. This star, also called Cayrel’s star, was found to be more metal deficient than the globular clusters, and was likely born in the Galaxy during very early times. This measurement, carried out with the high-resolution UVES spectrograph of the ESO/VLT telescope, gave rise to the determination of the age of formation of U and Th in the early Galaxy, using, for the first time, the U/Th ratio. The derived uranium abundance yielded an age 12.5 ± 3 Gyr, which led to the best estimate of the age of the Galaxy and consequently provided a lower limit to the age of the Universe. However, as mentioned by Cayrel et al. ( 2001b ), the accuracy of this uranium dating is still affected by uncertainties in the measured abundance ratio, and in the calculated U/Th production ratio. The improvement of this situation depends not only on a better estimation of the production ratio U/Th, on advances in nuclear astrophysics models and on the investigation of other stars in which U and Th can be detected, but also on a comprehensive knowledge of the radiative properties for the potentially observable spectral lines, notably for the strongest U ii electric dipole transitions. To our knowledge, there have been very few available calculations of radiative parameters for singly ionized uranium so far. The main reason is that the complexity of the strongly mixed states involved in the lowest configurations, with five electrons distributed on the 5f, 6d, 7s, and 7p subshells, and the fragmentary knowledge of the experimental spectrum of this ion made theoretical computations extremely difficult. Most of the available oscillator strengths were deduced from quite old line intensities measured on arc spectra (Meggers, Corliss Schribner 1961 , Corliss Bozman 1962 , Voigt 1975 , Corliss 1976 , Kurucz 1995 ) if we except the results published by Nilsson et al. ( 2002 ) who obtained accurate gf values by combining branching fraction measurements with laboratory lifetimes determined using laser spectroscopy (Lundberg et al. 2001 ). These latter data concern however only a small number of strong U ii lines. This lack of reliable radiative parameters in singly ionized uranium justifies the work reported in this paper. An additional motivation was also found in the new analysis of the experimental spectrum recently published for this ion by Meftah et al. ( 2017 ). More precisely, we carried out detailed calculations of oscillator strengths for the strongest U ii transitions using the pseudo-relativistic Hartree-Fock (HFR) method (Cowan 1981 ) with core-polarization corrections (HFR+CPOL; Quinet et al. 1999 , 2002 , Quinet 2017 ). This allowed us to draw up a list of 38 visible spectral lines that could be used in cosmochronology. 2 AVAILABLE ATOMIC DATA IN U <sc>ii</sc> In their critical compilation related to actinides, Blaise Wyart ( 1992 ) listed some preliminary U ii energy levels, using the emission lines listed by Steinhaus et