Experimental testing and numerical simulations for life prediction of gate valve O-rings exposed to mixed neutron and gamma fields

D Battini,G Donzella,A Avanzini,A Zenoni,M Ferrari,A Donzella,S Pandini,F Bignotti,A Andrighetto,A Monetti

doi:10.1016/j.matdes.2018.07.020

Abstract

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 were 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.

Highlights

The selective production of exotic species (SPES) facility at the Legnaro National Laboratories of INFN [1] is a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams (RIBs).D
The effects of neutron radiations on gasket materials and structural components in general are quite undocumented compared to the effects of γ radiations
Contact pressure distributions showed to be very sensitive to the absorbed dose as the material became noticeably stiffer at higher dose levels

Summary

Introduction

The selective production of exotic species (SPES) facility at the Legnaro National Laboratories of INFN [1] is a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams (RIBs).D. The selective production of exotic species (SPES) facility at the Legnaro National Laboratories of INFN [1] is a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams (RIBs). The radioactive nuclear species are produced by fission of a 238U target induced by an intense proton beam. Materials and components employed for the construction of the SPES TIS are exposed to a highly radioactive environment, with neutron and gamma fields whose fluxes around the target are of the order of 1010 particles/(cm s) [2]. In order to carry out this automated removal, valves are required to isolate the TIS and prevent the release of radioactive contaminants in the storage environment.

Methods

Results

Conclusion