An Irradiation Campaign of Lubricants at TRIGA Mark II Nuclear Reactor for the European Spallation Source (ESS) and the Selective Production of Exotic Species (SPES) facilities

Materials and components used in the neighbourhood of high power targets for spallation neutrons and radioisotopes production work in a very radioactive environment, characterized by intense neutron and gamma fields. The absorbed doses may induce substantial degradation of their physical and mechanical properties, which can lead to a premature structural failure, compromising machine operations. The European Spallation Source project (ESS) in Lund, Sweden and the SPES (Selective Production of Exotic Species) project of the Italian Institute of Nuclear Physics (INFN) in Legnaro, Italy are currently in the construction phase. Among the polymeric materials, known to be the most radiation sensitive, lubricating greases are crucial for a reliable operation of their target stations. Experimental campaigns aimed at testing the neutron radiation-induced lubricants degradation are ongoing. Data from post-irradiation examinations are used to estimate the radiation resistance of the materials in operation, leading to the best product choice. Irradiations are performed in the Central Thimble of the TRIGA Mark II research nuclear reactor of the LENA laboratory of the University of Pavia. The reactor neutron and photon mixed field is used to reproduce as close as possible the actual environmental service conditions. Considered materials were previously tested for radiation hardness mainly in gamma radiation fields.