Study of the 60Ni(n,2n)59Ni reaction from threshold to 20 MeV and the half-life of 59Ni

The production of long-lived Ni-59 as activation product is of concern for a fusion environment. Its main production is the (n,2n) reaction of 14-MeV neutrons on stable Ni-60 with some additional contributions from neutron capture reactions on Ni-58 via lower energy neutrons. Information for the production of Ni-59 via the (n,2n) reaction is strongly discordant or completely missing. Ni metal samples were available to us which had previously been irradiated with neutrons at energies of 17 and 19 MeV. After the irradiation the amount of produced Ni-59 was measured via accelerator mass spectrometry utilizing the 14-MV tandem accelerator of Maier-Leibnitz Laboratory in Munich. A second important issue is the half-life of Ni-59: The accepted value is t(1/2) = (76 +/- 5) kyr which is substantially lower than the value of (108 +/- 13) kyr which was obtained a few years later in an independent measurement. The later value is based on relative measurements using the thermal Fe-54 neutron capture cross section. A new measurement of this cross section is underway at the VERA laboratory in Vienna applying AMS for the quantification of Fe-55. The new data will allow to generate a more precise value for the half-life of Ni-59 compared to the previous one.