Neutron skyshine from intense 14MeV neutron source facility

The dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured in the environment surrounding an intense 14 MeV neutron source facility. The source neutrons produced by D-T reaction penetrate 20-cm-thick concrete ceiling and upper part of side wall, and leak into atmosphere. The dose distribution and the energy spectra of neutrons around the facility to be a skyshine source have also been measured to enable the absolute evaluation of the skyshine effect. The skyshine effect was analyzed by two multigroup Monte Carlo codes, by discrete ordinates Sn code, and by the shield structure design code for skyshine. The calculated results show good agreement with the measured results in absolute values. These results must be useful as a kind of benchmark experiment on the skyshine phenomenon, as well as for shielding design of fusion facilities