Fire behavior of lead-containing PMMA based Kyowaglas

International audienceIn the present work, the flammability of Kyowaglas is characterized experimentally. Kyowaglas is a lead-based composite used in glove boxes of nuclear facilities as a biological protection against radiation. It consists of 70%wt PMMA (Poly(Methyl Methacrylate)) and 30%wt leaded compounds. The aim of the study is to understand the role and impact of lead during the combustion of Kyowaglas in order to deepen knowledge of its thermal and fire behavior. A comparative study between Kyowaglas and virgin PMMA is conducted to better understand the effect of lead on the combustion process of these materials. Fire behavior is studied using cone calorimeter, pyrolysis-combustion flow calorimeter and thermogravimetric analysis. At different stages of cone calorimeter test, the samples and residues were examined and characterized using different experimental techniques like microscopy, spectroscopy, X-ray diffraction and calorimetry. Thermal analysis data show that lead seems to slightly accelerate the decomposition of PMMA under inert atmosphere. However, it confers significant thermal stability during a cone test due to the accumulation of lead on the surface of the sample. As the Kyowaglas burns, metallic lead is formed and accumulated at the top surface slowing down the heat transfer. At the end of the cone calorimeter test, lead oxide beads start to form on the surface of the residue due to the oxidation of metallic lead

Limestone-Siliceous and Siliceous concretes thermal damaging at high temperature

Pré-publication : Construction and Building Materials 228 (2019) 116671Limestone-siliceous and siliceous concretes are used in reactor pits of French nuclear power plants. In case of severe nuclear reactor accident, failure of the reactor vessel would lead to interaction between molten corium (hot melt of nuclear fuel) and concrete. This paper focuses on the thermal degradation of both limestone-siliceous and siliceous concretes till 1000°C. Thermo-Gravimetric Analysis (TGA) and Mercury Intrusion Porosimetry (MIP) are used to measure mass loss and porosity modification. As concretes are heterogeneous materials, sampling and representativeness have been addressed. TGA experiments show larger mass loss for limestone-siliceous concretes due to the decarbonation of calcium carbonate gravels when T>800°C. MIP experiments demonstrate a 100% increase of porosity for limestone-siliceous (resp. siliceous) concretes when T> 500°C (resp. T> 800°C). The consequences of these results are discussed in the frame of experimental tests on prototypical corium systems aimed at describing the key-phenomena involved in molten corium concrete interaction

Standardisation of a new model of H9N2/Escherichia coli challenge in broilers in the Lebanon

Primary infection by low pathogenic avian influenza (LPAI) predisposes for secondary infection by Escherichia coli in poultry, leading to significant economic losses. Future research in control of this ailment requires the establishment of a successful controlled challenge by avian influenza virus (AIV)/E. coli. Six groups of broilers (6 birds/group) were included for the standardisation of the controlled challenge by AIV/E. coli. Birds in groups 1, 2, 3, 4 and 5 received an intra-tracheal challenge of 0.5 ml of two haemagglutinating units of H9N2 virus at 20 days of age. At the age of 23 days, birds in group 1 received an intra-thoracic (right air sac)-E. coli challenge equivalent to 1.6 × 109 colony-forming units (cfu)/0.5 ml/bird, while birds in groups 2, 3, 4 and 5 received E. coli by the same route and in the following respective decreasing order of viable cells: 1.6 × 106, 1.6 × 105, 1.6 × 104 and 1.6 × 103 cfu. Birds in control group 6 were deprived of H9N2 and E. coli challenge. Results showed significant early mortality in group 1 that was challenged with the highest number of E. coli, in comparison to groups 2-6 (p0.05). The frequencies of four signs at 2 days and at 5 days post E. coli challenge (conjunctivitis, diarrhoea, ocular exudates and rales) in the surviving birds of groups 2-5 were most often higher than those observed in control group 6 (p<0.05). These four signs and five gross lesions (abdominal airsacculitis, left thoracic airsacculitis, pericarditis, right thoracic airsacculitis and tracheitis) had a decreasing pattern of frequency related to a decrease in the E. coli count used in the challenge