Radio-oxidation ageing of XLPE containing different additives and fillers: effect on the gases emission and consumption

International audienceIn the lifetime extension of nuclear power plants (NPPs) context, aging of electric cables has to be very well understood in order to predict their end-of-life and thus to replace them on time. Therefore, evaluation and understanding of the ageing mechanism of the cable insulating material is mandatory under conditions as close as possible of those encountered in NPPs. In this context, different formulated crosslinked polyethylenes (XLPE)—one of the polymers used nowadays to manufacture the insulator layer—have been irradiated under oxidative conditions, at two different dose rates and at different aging doses. Gases emitted and consumed from the irradiated polymers were quantified to identify the primary processes happening in the materials and thus the interactions involved between the different molecules composing the formulated polymer

240^{240}Pu/239^{239}Pu isotopic ratio measurements in micrometric Pu and MOX particles using Secondary Ion Mass Spectrometry

International audienceEvery accident affecting industrial or nuclear facilities emits micrometric fragments of material into the environment whose elemental and isotopic compositions are characteristic of the process or event. Particle analysis, mainly implemented in the framework of the Non Proliferation Treaty to detect clandestine nuclear activities, provides a powerful tool to identify the origin of the nuclear particulate matter and to assess the environmental impact of nuclear accidents. Initially, particle-scale isotopic analyses aimed at the determination of the U isotopic composition. Now, focus is increasingly given on Pu isotopic measurements to address its origin and potential use. Such measurements are more challenging because of isobaric interferences, including those induced by hydride ions, like $^{239}$PuH+ on $^{240}$Pu+ and $^{238}$UH+ on $^{239}$Pu+ in Mixed Oxide (MOX). Such ions are generated during ionization processes by Secondary Ion Mass Spectrometry. Based on a parametric study aiming at the measurement of uranium oxide, uranium carbide and uranium single and double hydride rates, we determined that Pu and U should be detected as elementary ions to limit the impact of such interferences, although mono-oxide ions are more abundant. Thus, we developed an analytical methodology to obtain accurate$^{240}$Pu/$^{239}$Pu atomic ratios both for weapon grade Pu and MOX materials. Hydride rate is first measured in U oxide particles and then applied to correct $^{240}$Pu+ and $^{239}$Pu+ signals. The relative difference of corrected $^{240}$Pu/$^{239}$Pu isotopic ratios with expected values is reduced by a factor of 4 when measuring weapon grade Pu particles and by a factor of 10-100 when measuring MOX particles containing 1 to 10 wt% of Pu. We also proposed a method to determine the Relative Sensitivity Factor (RSF) based on the decay of Pu in order to quantify the Pu content in MOX samples. The estimated lowest measurable $^{239}$Pu/$^{238}$U atomic ratio in MOX particles is ∼1.6 × 10$^{-3}

Atmosphere and dose effects on the SHI irradiation of atactic polystyrene

International audienceThis article deals with the Swift Heavy Ion (SHI) irradiation of atactic polystyrene at different doses, up to about 10 MGy, under an inert as well as under an oxidative atmosphere. The effect of the irradiation is adressed using various analytical tools such as high-resolution gas mass spectrometry, gel fraction, size exclusion chromatography, and Fourier Transform InfraRed spectroscopy. It has been evidenced that under SHI, in conditions of homogenous oxidation, part of the defects identified are those commonly observed under an oxidative atmosphere with low linear energy transfer irradiations (hydroperoxides and carbonyl bonds for instance) and part of the observed defects are those generally observed under inert atmosphere (C=C bonds...). This specific effect is assigned to the heterogeneous structure of energy deposition with ion beams. More precisely, this is due to the high ionization and excitation density in ion tracks. PS is known to be very radiation-resistant under inert atmosphere. Althought degradation is increased under oxidative atmosphere, the oxidation remains very low compared to the one observed in polyethylene; even at doses as high as 10MGy. This shows the efficiency of the radiation protection effect of the aromatic rings under oxidative atmosphere

Atmosphere and dose effects on the SHI irradiation of atactic polystyrene

International audienceThis article deals with the Swift Heavy Ion (SHI) irradiation of atactic polystyrene at different doses, up to about 10 MGy, under an inert as well as under an oxidative atmosphere. The effect of the irradiation is adressed using various analytical tools such as high-resolution gas mass spectrometry, gel fraction, size exclusion chromatography, and Fourier Transform InfraRed spectroscopy. It has been evidenced that under SHI, in conditions of homogenous oxidation, part of the defects identified are those commonly observed under an oxidative atmosphere with low linear energy transfer irradiations (hydroperoxides and carbonyl bonds for instance) and part of the observed defects are those generally observed under inert atmosphere (C=C bonds...). This specific effect is assigned to the heterogeneous structure of energy deposition with ion beams. More precisely, this is due to the high ionization and excitation density in ion tracks. PS is known to be very radiation-resistant under inert atmosphere. Althought degradation is increased under oxidative atmosphere, the oxidation remains very low compared to the one observed in polyethylene; even at doses as high as 10MGy. This shows the efficiency of the radiation protection effect of the aromatic rings under oxidative atmosphere