KI and TEDA influences towards the retention of radiotoxic CH3I by activated carbons

Activated carbons (AC) are widely used within the ventilation networks of nuclear facilities to trap volatile iodine species. In this paper, the performances of various commercial activated carbons towards the trapping of γ-labelled methyl iodide were evaluated in semi-pilot scale under different R.H. according to normalized procedures. A combination between the retention performances and the physico-chemical properties as deduced from several techniques was performed to gain insights about the AC influencing parameters on γ-CH₃I capture. Different trends were obtained depending on the impregnant nature and the studied conditions. A high sensitivity of KI/AC towards water vapor was outlined. At R.H. = 40%. The enhancement of water uptake by KI/AC as deduced from water adsorption experiments, leads to decrease the available microporosity for CH₃I physisorption, inducing therefore the reduction of performances as a function of KI content at these conditions. At R.H. = 90%, the adsorption mechanism was found to be governed by isotopic exchange reaction since 90% of the microporosity was occupied by water molecules. Therefore, a slight increase of DF was obtained in these conditions. This sensitivity was found to be of a lesser extent for TEDA/AC displaying the highest retention performances whatever the studied condition.

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

In 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.

[Biliary lithiasis in cystic fibrosis. Study of the bile salts in the serum and in the bile in one case (author's transl)]

Biliary lithiasis was discovered in a girl aged 11 suffering from Cystic Fibrosis and who underwent partial small bowel resection for meconium ileus. A cholecystectomy was performed at 15. Examination of the stones showed that they were composed of cholesterol and chemical examination of the bile showed an increase of phospholipids and a decrease in bile salts. There was also a modification of the ratio (Formula: see text) in the serum and the bile. All those factors contribute to the insolubility of cholesterol and to the formation of lithiasis. For all those reasons, the authors recommend a regular radiologic surveillance of the gallbladder in Cystic Fibrosis.