Radiation Damage by High-Energy Neutrons

Graphite rods and vitreous silica blocks were exposed to the neutrons generated in a spallation source having a large flux component in the 100-MeV region. The electrical conductivity of the former and the dilatation of the latter were measured. The ratio of the damage rate in silica to that in graphite exceeded that reported for fission neutrons, and this is attributed to the scattering cross sections of carbon falling more in the neutron high-energy region than do those of silicon and oxygen. Within our knowledge of the fluxes and their spectra and the yield functions, no great enhancement of the damage rate is found as compared to that which would be calculated from simple isotropic scattering.