Effects of water vapour and temperature on the retention of radiotoxic CH3I by silver faujasite zeolites

International audienceIn this work, Ag/X and Ag/Y faujasite zeolites were evaluated as candidate sorbents for the retention of methyl iodide under conditions close to those expected in a severe nuclear accident. Different categories of tests were conducted from laboratory to semi-pilot scales. First, the effects of temperature and water vapour on the CH3I retention/decomposition mechanism were investigated under lab-scale conditions. More specifically, the CH3I adsorption capacities and the fate of its main decomposition products (oxygenated compounds and alkanes) were measured under dynamic conditions at different temperatures (35, 100 and 250 °C). Then, the decontamination factors of Ag/X and Ag/Y silver faujasites exchanged with different silver contents were monitored according to the time on stream using a very low CH3I concentration (1 ppmv). Finally, a parametric study was conducted at semi-pilot scale using realistic [CH3I]/[H2O] molar ratio ≈ 10−6 and temperatures in the range 20–90 °C. Those experiments were helpful in order to assess the effects of some important parameters relevant to the adsorbents or operating conditions

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))

Effect of activated carbons properties towards the capture of methyl iodide: first insights about the isotopic exchange contribution

International audienceTEDA and KI co-impregnated activated carbons (ACs) are widely used in the nuclear facilities to prevent volatile iodine species (namely CH3I) dissemination into the environment. However, some uncertainties still remain namely about the most influencing adsorbent parameters, as well as the involved adsorption mechanisms. In this talk, a specific attention will be devoted to better assess the influence of KI progressive impregnation on the obtained retention performances through different test methodologies and using various characterization techniques (XPS, SEM/EDS, N2 porosimetry, H2O porosimetry…). Different trends were obtained depending on the studied condition when considering CH3I retention efficiency as deduced from standardized protocols. A decrease of decontamination factors (DF) was observed as a function of KI content at R.H. = 40 % (Fig.1 (A)). This decrease was attributed to the enhancement of H2O interaction with activated carbons after KI impregnation. Therefore, the available microporosity for CH3I physisorption is reduced (Fig.1 (A)). At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction, leading therefore to a slight DF increase after progressive KI incorporation. Better performances were nevertheless obtained after TEDA impregnation due to its high affinity with methyl iodide [1]. The beneficial effect of KI for CH3I removal was highlighted namely through breakthrough experiments performed towards γ-labelled and stable CH3I. Indeed, a progressive gain in adsorption capacities after KI incorporation until about 70% for 5%KI/AC, was evidenced (Fig. 1 (B))

Isotopic exchange inside impregnated activated carbons

International audienceActivated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. The present study aims to gain insights on the importance of isotopic exchange reaction resulting from KI as a comparison with other mechanisms (physisorption and chemisorption). The presence of isotopic exchange in some configurations has been qualitatively proven. However, the quantification of this reaction must be evaluated by comparing the breakthrough curves in active and inactive. Hence, a specific test bench allowing the determination of breakthrough curve in active is under validation

Isotopic exchange inside impregnated activated carbons

International audienceActivated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. The present study aims to gain insights on the importance of isotopic exchange reaction resulting from KI as a comparison with other mechanisms (physisorption and chemisorption). The presence of isotopic exchange in some configurations has been qualitatively proven. However, the quantification of this reaction must be evaluated by comparing the breakthrough curves in active and inactive. Hence, a specific test bench allowing the determination of breakthrough curve in active is under validation

Isotopic exchange inside impregnated activated carbons

International audienceActivated carbons (AC) have been used for the removal of iodine within ventilation networks of nuclear facilities. More particularly, the commonly used nuclear grade AC are co-impregnated with potassium iodide (KI, 1 wt%) and triethylenediamine (TEDA, < 5 wt%) [1]. The present study aims to gain insights on the importance of isotopic exchange reaction resulting from KI as a comparison with other mechanisms (physisorption and chemisorption). The presence of isotopic exchange in some configurations has been qualitatively proven. However, the quantification of this reaction must be evaluated by comparing the breakthrough curves in active and inactive. Hence, a specific test bench allowing the determination of breakthrough curve in active is under validation

Untargeted metabolomics studies focusing on prognosis and resistance factors leading to the identification of new potential biomarkers in equine atypical myopathy

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Untargeted metabolomics studies focusing on prognosis and resistance factors leading to the identification of new potential biomarkers in equine atypical myopathy

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Comment confirmer le diagnostic de myopathie atypique ?

National audienc