Method of preventing fine cracks from occuring in rubber or plastic insulation of an insulated wire or cable exposed to electron beam irradiation

A method of preventing fine cracks from occurring in the insulation of an elongated insulated wire or cable having a rubber or plastic insulation layer which has a maximum wall thickness of electron beam penetration of 4 mm or over and whose properties are improved by irradiation with an electron beam,

• the method comprising:
• longitudinally running the wire or cable under a scanner of an electron beam accelerator while rotating said wire or cable about the longitudinal axis thereof at such a speed as causes the same portion of the wire or cable to be irradiated with the electron beam of the electron beam accelerator at least twice during a period of less than 10 seconds;
• and
• causing the electron beam accelerator to deliver on the insulation layer of the wire or cable an electron beam which is accelerated to an energy of 1 MeV or over and whose maximum penetration range in the said insulation layer is larger than its thickness.