Sealed operation, and circulation and purification of gas in the HARPO TPC

HARPO is a time projection chamber (TPC) demonstrator of a gamma-ray telescope and polarimeter in the MeV-GeV range, for a future space mission. We present the evolution of the TPC performance over a five month sealed-mode operation, by the analysis of cosmic-ray data, followed by the fast and complete recovery of the initial gas properties using a lightweight gas circulation and purification system.Comment: Proceedings_MPGD2015, EPJ Web of Conference

Fulvestrant: an oestrogen receptor antagonist with a novel mechanism of action

Due to their favourable tolerability profiles, endocrine therapies have long been considered the treatment of choice for hormone-sensitive metastatic breast cancer. However, the oestrogen agonist effects of the available selective oestrogen receptor modulators, such as tamoxifen, and the development of cross-resistance between endocrine therapies with similar modes of action have led to the need for new treatments that act through different mechanisms. Fulvestrant (‘Faslodex’) is the first of a new type of endocrine treatment – an oestrogen receptor (ER) antagonist that downregulates the ER and has no agonist effects. This article provides an overview of the current understanding of ER signalling and illustrates the unique mode of action of fulvestrant. Preclinical and clinical study data are presented in support of the novel mechanism of action of this new type of ER antagonist

Thermal decomposition of radio-oxidized polymers and impact on radioactive material transportations

International audienceIntroductionIn case of accidental conditions of transportation, the temperature of packages can reach 150°C. Theaccumulation of the gases formed may affect the integrity of the package. Therefore, it is important topredict the gas quantity released by different organic materials and measure the kinetic of thisdecomposition. The purpose of this work is to present the results of a multi-year study performed on fourpolymers (polyethylene, cellulose, polyurethane, polyvinyl chloride). The effect of dose, atmosphere anddegradation temperature on the quantity of gas release was investigated.ExperimentalThe polymers were gamma-irradiated under air atmosphere at room temperature at different doses (from 0to 4 MGy). After irradiation, the thermal degradation of polymers at different temperatures (from 60°C to150°C) during 48 hours under two types of atmosphere (air or inert) was analyzed. For that purpose, aknown amount of polymer was conditioned in a small hermetic chamber (made on stainless steel or glass)equipped with a pressure gauge. The pressure elevation during the thermal treatment was recorded. Anidentification and a quantification of the gas phase were also realized using high resolution massspectrometry.Results and discussionIn contrast to the non-irradiated polymers, which are mostly stable even at 150°C, a rapid increase of thepressure during the first hours after heating and a stabilization or a slow increase after is observed for radiooxidized materials. The production of volatile species is almost proportional to the dose and is thermallyactivated. The main degradation products are water and carbon dioxide. The production of hydrogen andinflammable gases is rather limited. Under air atmosphere, the pressure increase is partially compensatedby oxygen consumption.ConclusionsThe thermal decomposition of pre-oxidized polymers is rapid. The majority of the gases is released in thefirst hours. Water and carbon dioxide are the predominant species. Although irradiation reduces the thermalstability of the polymers, our results show that the risk of inflammation is not exacerbated

Thermal decomposition of radio-oxidized polyethylene

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Thermal decomposition of radio-oxidized polymers

International audienceMany polymers are used in nuclear industry and are then stored in nuclear waste packages. In case of accidental conditions of transportation, the temperature of packages may increase and reach 150°C. The accumulation of the gases formed may affect the integrity of the waste container. Therefore, for safety purpose, it is important to predict the gas quantity released by different organic materials and measure the kinetic of thermal decomposition of radio-oxidized polymers. The purpose of this work is to present the results of a multi-year study performed on four polymers (polyethylene, cellulose, polyurethane, polyvinyl chloride). The effect of dose, atmosphere and degradation temperature on the quantity of gas release was investigated

Radiation effects on a linear model compound for polyethers

No commentInternational audienceRadiation effects on a model polyether - poly(tetramethylene) glycol (PTMG) induced by high energy radiation were investigated. To understand the degradation mechanism, electron paramagnetic resonance (EPR), Fourier transform infra-red spectroscopy (FTIR), electrospray and gas mass spectrometry (ESI-MS and gas-MS), were carried out to identify radicals and chemical modifications. Size exclusion chromatography (SEC) was used to follow the evolution of the distribution of molecular weight. On the basis of the results, a mechanism of degradation for PTMG is proposed. © 2011 Elsevier Ltd. All rights reserved

Influence de la température sur la formation de volatiles au cours du vieillissement thermo-oxydant de blindages neutroniques pre-irradies

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Original behavior of pore water radiolysis in cement-based materials containing sulfide: coupling between experiments and simulations

International audienceBlended cements with high content of blast furnace slag (CEM III/C) can be used for nuclear waste conditioning because of their low hydration heat as compared to ordinary Portland cements (CEM I). They however contain some sulfide, an impurity whose role needs to be investigated. Indeed, they can have an effect on the radiolytic H2 production under irradiation. To study the impact of sulfide species on H2 production, gamma irradiation, at a dose rate of 356Gyh−1, was performed during 6 months in a closed system without O2 on a cement paste made with CEM III/C. At short time, the radiolytic H2 production rate is higher than that measured using CEM I. On the basis of reaction data collected in the literature on sulfur species, radiolysis simulations performed for both systems confirm this behavior. Moreover, they suggest that the sulfide concentration, initially imposed in pore solution by the slag is of the order of 180mM, and is responsible for this H2 production. For the first two irradiation months, the following phenomena are then evidenced in CEM III/C: 1) conversion of sulfide into polysulfide anions; 2) pH increase; 3) production of H2 due to the H•+ H2S reaction having a very high rate constant. Nevertheless, in the medium term, the residual sulfide concentration is not sufficient any more for this mechanism to occur. It imposes a reducing environment, leading to a very efficient recombination of H2 in pore solution. The resulting equilibrium state is reinforced by the high liquid saturation level in the cement paste porosity. Therefore, even if the presence of sulfide species in blended cements momentarily increases the H2 production rate, it strongly reduces it at long times