A number of glass samples were prepared from a mixture of Na2B4O7 and CuO. The prepared glasses were irradiated with a low-level fast neutron beam (flux density 108 n cm−2). The alternating current (a.c.)-electrical conductivity and the dielectric constant at a frequency of 1 kHz of these glasses have been studied as a function of temperature in the range 300–600 K. The measurements showed that an amorphous–crystalline phase transition characterized these samples. This phase transition was affected by neutron irradiation. Also a decrease in the activation energy for the irradiated undoped sample and an increase in the activation energy for the irradiated doped samples were found. After irradiation, the maximum peak, which characterized the dielectric constant of the samples before irradiation, disappeared.