Aging of magnesium stearate under high doses gamma irradiation and oxidative conditions

•Magnesium stearate was radio-oxidized at very high doses using gamma-rays.•H2 emission was estimated as a function of the integrated dose.•Modifications in the organic solid were followed as a function of the integrated dose.•A non-exhaustive degradation mechanism of magnesium stearate was proposed. In nuclear waste packages conditioning processes, magnesium stearate is widely used because of its high lubricating properties. For safety purposes, the radiolytic degradation of these organic materials has to be better understood to be able to predict their aging in repository conditions. This study reports the radiolytic degradation of magnesium stearate, using gamma-rays at room temperature and under air. Modifications were followed using different analytical tools (XPS, ATR-FTIR, ICP-AES, ATG and mass spectrometry). It has been observed that molecules mainly formed up to 1000kGy of gamma irradiation dose under radio-oxidation are alkanes, hydroperoxides, double bonds in the aliphatic chain, carboxylates with aliphatic chain shorter than the one of stearate and ketones. At a dose of 4000kGy, dicarboxylic acids are observed: the formation of these molecules needs a dose of at least 1000kGy to be created under radio-oxidation. These observations allow us to propose a non-exhaustive degradation mechanism of magnesium stearate under gamma-irradiation at room temperature and under air.