Neutron-induced opalescence in silica glass

Light scattering intensity distribution along the optical fiber length is analyzed, which was measured by optical time domain reflectometry (OTDR) during and after fiber irradiation in a nuclear reactor. The OTDR traces prove to contain two components associated with either radiation-induced attenuation (RIA), or with Rayleigh scattering coefficient (RSC) variation. The RSC increase effect in the first stage of fast-neutron irradiation is argued to be similar to the anomalous scattering buildup near the critical point of the liquid-vapor transition known as critical opalescence. For his reason, the RSC increase due to fast-neutron irradiation can be named neutron-induced opalescence (NIO).