Available online xxxx EPDM O-rings of gate valves employed for the construction of a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams were studied in order to assess their sealing performance both during the facility service time and the post-service storage phase. Several O-ring specimens were at first exposed to different dose levels of mixed neutron and gamma radiations. Correspondent modifications of physical and mechanical properties of the material

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... e investigated by means of uniaxial tensile tests, dynamic mechanical analyses, aging, compression set and vacuum leak tests. A hyperelastic strain energy function was adopted to fit the mechanical response of the material as a function of the absorbed dose. The minimum squeeze degree that guarantees O-ring sealing efficiency at different irradiation levels was determined by varying the interference between O-rings and grooves. A finite element model of the vacuum leak test was then set up to assess the contact pressure level required to ensure sealing. Numerical simulations of the gate valve main O-ring were subsequently carried out. By comparison of the predicted contact pressure and strain levels with experimental results, a life prediction map, as function of the service time, the storage time and the O-ring squeeze degree, was proposed.