Determination of spatial and energy distributions of neutrons in experiments on transmutation of radioactive waste using relativistic protons

The experiments on transmutation of I-129 and Np-237 using uranium-lead targets surrounded by a paraffin moderator were performed at the Joint Institute for Nuclear Research (JINR, Russia). The targets were irradiated by 1.5 GeV and 7.4 GeV protons at the Synchrophasotron of JINR. In the frame of present work spatial and energy distributions of neutrons on the surface of the paraffin moderator were measured using SSNTD technique. It is shown that measured values of spectral indices do not depend on the energy of incident protons but depend on the target composition. The presence of the uranium insertion softens neutron spectra.