Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results

Review of Scientific Instruments - Tập 88 Số 11 - 2017
A. Zenoni1,2,3, Fabio Bignotti1,2, A. Donzella2,3, Giorgio Donzella2, Matteo Ferrari2,3, Stefano Pandini1,2, A. Andrighetto4, M. Ballan5,4, S. Corradetti4, M. Manzolaro4, A. Monetti4, M. Rossignoli6,4, D. Scarpa4, D. Alloni7, Michele Prata7, Andrea Salvini7, F. Zelaschi7
1Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali INSTM, Unità di Ricerca di Brescia 2 , Via Branze 38, I-25123 Brescia, Italy
2Dipartimento di Ingegneria Meccanica e Industriale, Università degli Studi di Brescia 1 , Via Branze 38, I-25123 Brescia, Italy
3Istituto Nazionale di Fisica Nucleare 3 , Via Bassi 6, I-27100 Pavia, Italy
4Laboratori Nazionali di Legnaro dell’INFN 4 , Viale dell’Università 2, I-35020 Legnaro (PD), Italy
5Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara 5 , Via G. Saragat 1, I-44122 Ferrara, Italy
6Dipartimento di Ingegneria Industriale, Università degli Studi di Padova 6 , Via Venezia 1, I-35131 Padova, Italy
7Laboratorio Energia Nucleare Applicata LENA, Università degli Studi di Pavia 7 , Via Aselli 41, I-27100 Pavia, Italy

Tóm tắt

Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects and oxygen penetration in the material, both during test irradiations and in operating conditions, is needed to obtain reliable predictions.

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Review of Scientific Instruments

Tập 88 Số 11

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