[en] The radiation-thermal degradation of several types of commercial cable insulation materials (semi-crystalline crosslinked polyolefins) was investigated. Annealing at elevated temperatures of samples that had been previously irradiated at or near room temperature led in some cases to significant recovery of mechanical properties (elongation at break) and concurrent changes in gel content (additional crosslinking) and density. A comparison of degradation in samples irradiated at different temperatures (in the range of 22 deg C to 120 deg C) showed that mechanical property deterioration surprisingly occurred most rapidly at the lowest temperatures. The importance of molecular mobility in the semi-crystalline materials and the nature of the additional crosslinking reaction as contributors to these anomalous behaviors are evaluated and discussed. The observed temperature effects are due to a combination of the semi-crystalline morphology of the materials, and a specific crosslinking reaction, which can act as a repair mechanism at elevated temperatures, but is dormant at ambient conditions. The beneficial thermal annealing which can result in substantial recovery of useful mechanical properties in this type of material is reminiscent of the beneficial annealing phenomenon that results in the recovery of optical transmittance properties of glassy polymers, which we have reported on recently. (author)