Radiation damage assessment of the sixth SINQ target irradiation program based on MCNPX simulation

The 6th SINQ Target Irradiation Program (STIP VI) was conducted in SINQ Target 9 during 2011 and 2012. A radiation damage assessment based on a simulation using the MCNPX code was performed to obtain the irradiation parameters of displacement damage, helium and hydrogen concentrations in each specimen rod placed in the target. The gamma mapping performed on the proton beam entrance window after irradiation provided the proton fluence distribution used for implementing the source definition in the simulation. The proton and neutron fluences along the target as well as the energy deposition were calculated. Corresponding to the average beam current of 1.42 mA, the maximum neutron flux obtained is 5.95 x 10(14) n/(cm(2). s) and the maximum energy deposition in the Zircaloy-2 cladding tubes is 568 W/cm(3). The irradiation parameters of selected materials in each specimen rod were calculated by multiplying the proton and neutron fluences with the corresponding cross section data. The maximum displacement damage was obtained for Zircaloy-2 in Row 2 with a value of 72.1 dpa (displacement per atom). The maximum helium concentration was obtained for tantalum in Row 1 with a value of 3630 appm and the maximum hydrogen concentration was obtained for tungsten in Row 1 with a value of 17590 appm. All these values are the highest for the corresponding materials ever reached in a spallation target irradiation environment. The helium concentrations are also the highest ever obtained in bulk specimens.