Neutron Radiation Effects on Lubricants and O-Rings for Target and Accelerator Applications

Abstract:

Lubricants and O-rings are necessarily used for the construction of many accelerator-driven facilities as spallation sources or facilities for the production of radioactive isotopes. During operation, such component will absorb high doses of mixed neutron and gamma radiation, that can degrade their mechanical and structural properties. Experimental radiation damage tests of these components are mandatory for the construction of the facility. Methodologies for irradiation in nuclear reactor mixed fields and post-irradiation examination of lubricating oils, greases and O-rings were developed and are here presented. Samples were characterized with standard mechanical and physical-chemical tests. Parametric studies on the dose rate effects have been performed on O-rings. A case studies for a specific O-ring application in a gate valve has been developed. Some of the tested samples showed a dramatic change of their properties with dose, while others remain stable. Results were collected on nine commercial greases, on one oil and on four commercial elastomeric O-rings. The most radiation resistant among the selected products are now considered for application in facilities under construction. The main mechanisms of neutron and gamma radiation damage on these polymers were investigated at the mechanical and structural level.

• Periodical: Materials Science Forum (Volume 1024)
• Pages: 127-133
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.1024.127
• Online since: March 2021
• Authors: Matteo Ferrari*, Aldo Zenoni, Yong Joong Lee, Alberto Andrighetto
• Keywords: Lubricant, Neutron Damage, O-Ring, Polymers, Radiation Damage, Radiation Resistance

References

[1] R. Garoby et al., The European Spallation Source design, Phys. Scr. 93 014001 (2018).

[2] A. Andrighetto et al., Spes: An intense source of Neutron-Rich Radioactive Beams at Legnaro, Journal of Physics: Conference Series, 966, 012028 (2018). doi.org/10.1088/1742-6596/966/ 1/012028.

DOI: 10.1088/1742-6596/966/1/012028

[3] M. Di Luzio, et al., Vertical variations of flux parameters in irradiation channels at the TRIGA Mark II reactor of Pavia, Progress in Nuclear Energy 113, 247-254 (2019).

DOI: 10.1016/j.pnucene.2019.01.025

[4] A. Zenoni, et al., Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results, Review of Scientific Instruments 88, 113304 (2017). doi.org/10.1063/1.5011035.

DOI: 10.1063/1.5011035

[5] M. Ferrari, et al., Experimental study of consistency degradation of different greases in mixed neutron and gamma radiation, Heliyon, Vol. 5, Issue 9, e02489 (2019). https://doi.org/10.1016/j.heliyon.2019.e02489.

DOI: 10.1016/j.heliyon.2019.e02489

[6] M. Ferrari, et al., The SPES Facility as an intense neutron source: radiation resistance of polymeric materials and residual activation calculations, Radiation & Applications, vol.3 issue 2, pp.98-105 (2018).

DOI: 10.21175/RadJ.2018.02.016

[7] MCNPX™ USER'S MANUAL, Version 2.7.0, April 2011, D. B. Pelowitz edit. (2011).

[8] M. Ferrari, et al., Degradation of EPDM and FPM elastomers irradiated at very high dose rates in mixed gamma and neutron fields, Polymer Engineering and Science, Vol. 59, Issue 12 (2019) https://doi.org/10.1002/pen.25249.

DOI: 10.1002/pen.25249

[9] D. Battini et al., Experimental testing and numerical simulations for life prediction of gate valve O-rings exposed to mixed neutron and gamma fields, Materials and Design 156, 514-527 (2018). https://doi.org/10.1016/j.matdes.2018.07.020.

DOI: 10.1016/j.matdes.2018.07.020