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

Overview of ¹⁴C release from irradiated zircaloys in geological disposal conditions

Carbon-14 (radiocarbon, 14C) is a long-lived radionuclide (5730 yr) of interest regarding the safety for the management of intermediate level wastes (ILW). The present study gives an overview of the release of 14C from irradiated Zircaloy cladding in alkaline media. 14C is found either in the alloy part of Zircaloy cladding due to the neutron activation of 14N impurities by 14N(n,p)14C reaction, or in the oxide layer (ZrO2) formed at the metal surface by the neutron activation of 17O from UO2 or (U-Pu)O2 fuel and water from the primary circuit in the reactor by 17O(n,α)14C reaction. Various irradiated and unirradiated Zircaloys have been studied. The total 14C inventory has been determined both experimentally and by calculations. The results seem to be in good agreement. Leaching experiments were conducted in alkaline media for several time durations. 14C was mainly released as carboxylic acids. Further, corrosion measurements were performed by using both hydrogen measurements and electrochemical measurements. The corrosion rate (CR) ranges from a few nm/yr to 100 nm/yr depending on the surface conditions and the method used for measurement. From a safety assessment point of view, the instant release fraction (IRF) was determined on irradiated Zircaloy-2. The results showed that the 14C inventory in the oxide was significantly below the 20% commonly used in safety case assessments

Resurgence of Ebola virus in 2021 in Guinea suggests a new paradigm for outbreaks

These authors contributed equally: Alpha K. Keita, Fara R. Koundouno, Martin Faye, Ariane Düx, Julia Hinzmann.International audienc

Determination of carbon-14 source term in French SIERs

International audienceCarbon Organic mass balance is calculated • ≈ 12 % is identified in LiOH "blank", virgin resins and SIERs solutions. • Only one organic compound identified in resin desorption solutions at very low concentration ≈ 1 % of Total Organic Carbon (TOC). • Identified carboxylic acids do not complete the carbon mass balance, even in LiOH solution. So, other molecules are in solution. , Contamination in LiOH makes difficult the determination of organic molecules in resin desorption solutions

A comparison of ASAP and DART ionizations for the analysis of polyurethanes and their additives.

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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 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

Determination of carbon-14 source term in French SIERs

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Superplasticizers degradation in a deep geological disposal for nuclear waste cementitious matrix an analytical investigation

International audienceThe conditioning by solidification in A cementitious matrix of radioactive waste coming from French nuclear industries is a widely used solution. For safety reasons it is important to evaluate and control the production of hazard flammable gas such as dihydrogen. Yet water in cementitious matrices ex-posed to ionizing radiation emitted by waste (radiolysis phenomenon) can contribute significantly to dihydrogen formation. The main objective of the Matrice project (Materials resistant to irradiation based on cement) with Leon Grosse, Vicat and CEA, Andra (The French National Radioactive Waste Management Agency) as partners is to optimize the formulations of cementitious materials in order to limit dihydrogen emissions to an acceptable level while optimizing the conditioning of highly radioac-tive waste. Most of investigated approaches require the addition of superplasticizers (SPs), which are water-reducing agents. Thus, it is important to study degradation of these compounds in the nuclear waste context. Radi-olysis and/or alkaline conditions can potentially induce formation of small organic molecules that can form stable complexes with radionuclides or affect radionuclide mobility. The objective of this study is to characterize the degradation molecules of two types of SPs a polyaromatic sulphonate (radioresistant but with poor plasticizing properties) and a polyether based superplasticizer (less radi-oresistant but with excellent plasticizing properties)

Analytical strategy for measurement of 14C in leachate of irradiated zirconium alloy hulls

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