Effect of Antioxidants on Radiation Stability of Polymers Used for Electric Cable Insulation

The effect of various antioxidants and antioxidant concentrations on the room-temperature radiation stability of ethylene propylene diene monomer (EPDM) and cross-linked polyethylene (XLPE) materials used as insulation for electric cable in nuclear power plants is measured. Relative elongation to rupture between aged and unaged material is used as the measure of stability. The materials are irradiated to doses up to 2.0 MGy (200 Mrad) at a dose rate of 300 Gy/h (3 x 10⁴ rad/h) in the Cobalt-60 Gamma Irradiation Facility at the University of Virginia. Several of the antioxidants in EPDM perform well to the maximum doses for which reliable data were obtained of either 1.0 or 1.6 MGy. An XLPE material with Agerite™ MA antioxidant performs well to the maximum dose for which reliable data were obtained of 1.0 MGy. Stabilization at 1.0 MGy increases with increasing antioxidant concentration, though not in proportion to the concentration.