Hello Antonio,
Wire and cable insulations can be crosslinked, albeit slowly, with high voltage electron beam (EB) radiation.
An initial company to contact would be Radiation Dynamics Inc. Their web site is
www.iba-worldwide.com/rdi/ Check out the RDI Menu on the right hand side and read the sections "Applications", "Science", and "E-Beam Theory"
Before high voltage electron beam machines, gamma radiation was sometimes used but that is now pretty much a dead issue for wire and cable.
Kindest regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com 
