Methods for The Testing of Nanopowder

Methods for the testing of nanopowders produced by wires electric explosion were considered. The following characteristics were proposed for the testing of nanopowders : main substance content, characteristic sizes of particles, specific surface area etc..Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Mycobacterium tuberculosis ecology in Venezuela: epidemiologic correlates of common spoligotypes and a large clonal cluster defined by MIRU-VNTR-24

<p>Abstract</p> <p>Background</p> <p>Tuberculosis remains an endemic public health problem, but the ecology of the TB strains prevalent, and their transmission, can vary by country and by region. We sought to investigate the prevalence of <it>Mycobacterium tuberculosis </it>strains in different regions of Venezuela. A previous study identified the most prevalent strains in Venezuela but did not show geographical distribution nor identify clonal genotypes. To better understand local strain ecology, we used spoligotyping to analyze 1298 <it>M. tuberculosis </it>strains isolated in Venezuela from 1997 to 2006, predominantly from two large urban centers and two geographically distinct indigenous areas, and then studied a subgroup with MIRU-VNTR 24 loci.</p> <p>Results</p> <p>The distribution of spoligotype families is similar to that previously reported for Venezuela and other South American countries: LAM 53%, T 10%, Haarlem 5%, S 1.9%, X 1.2%, Beijing 0.4%, and EAI 0.2%. The six most common shared types (SIT's 17, 93, 605, 42, 53, 20) accounted for 49% of the isolates and were the most common in almost all regions, but only a minority were clustered by MIRU-VNTR 24. One exception was the third most frequent overall, SIT 605, which is the most common spoligotype in the state of Carabobo but infrequent in other regions. MIRU-VNTR homogeneity suggests it is a clonal group of strains and was named the "Carabobo" genotype. Epidemiologic comparisons showed that patients with SIT 17 were younger and more likely to have had specimens positive for Acid Fast Bacilli on microscopy, and patients with SIT 53 were older and more commonly smear negative. Female TB patients tended to be younger than male patients. Patients from the high incidence, indigenous population in Delta Amacuro state were younger and had a nearly equal male:female distribution.</p> <p>Conclusion</p> <p>Six SIT's cause nearly half of the cases of tuberculosis in Venezuela and dominate in nearly all regions. Strains with SIT 17, the most common pattern overall may be more actively transmitted and SIT 53 strains may be less virulent and associated with reactivation of past infections in older patients. In contrast to other common spoligotypes, strains with SIT 605 form a clonal group centered in the state of Carabobo.</p

Heavy-ions induced scintillation experiments

International audienceThe French Alternative Energies and Atomic Energy Commission (CEA) is developing fission chambers relying on gas luminescence capable of high gamma signal rejection and self-diagnostic capabilities allowing high dependability level. Scintillation yield of noble gases by energetic ions (average initial energy between 68 MeV to 99 MeV) is evaluated for nuclear power reactor instrumentation application. Neutron interaction with fissile material can provide energetic heavy ions at a rate proportional to the neutron flux. The understanding of fission fragments as excitation source is required for noble gas scintillation neutron detectors. This work deals with evaluation of the optical signal heavy-ions induced in cold plasma. A dedicated experimental device (PSEG) is presented. Plutonium 238 is selected as a continuous source of heavy ions in order to avoid technological constraints of neutron flux tests, as a first step in the experimental validation process. Estimation of signal power is performed as well as Optical Emission Spectrum analysis. As expected, no Partial Local Thermodynamic Equilibrium is satisfied from experiments. The effect of pressure on the visible to infrared emission spectrum is analysed

Simulation of heavy-ion slowing-down tracks with the SCENA code

International audienceIn the frame of dependable neutron flux instrumentation development for Generation IV reactors, the French Atomic and Alternative Energies Commission (CEA) investigates an innovative technology based on optical signal produced withina fission chamber. In such gaseous detectors, neutrons interact with fissile material, releasing heavy ions in the MeV range, eventually leading to spontaneous photons emission in the ultraviolet to infrared range. We hereby present the space-time evolution of heavy-ion slowing-down tracks parameters in noble gases, as computed with the SCENA radiation-induced cold-plasma simulation tool. Preliminary results on excited-states noble-gas population dynamic are reported. Population of upper-lying gas levels is completed within picoseconds, only micrometers behind the projectile ionization trail

Design and irradiation test of an innovative optical ionization chamber technology

International audienceTo provide future dependable neutron ux monitoring instrumentation for sodium-cooled fast reactors (SFR) of Generation-IV, French Alternative Energies and Atomic Energy Commission (CEA) is investigating the applicability of an innovative technology based on the optical signal produced within any type of ionization chambers such as ssion chambers for instance. A mock-up of that innovative neutron detector was tested on a cold-neutron beamline at the ORPHEE nuclear facility. Experimental results regarding recovery time and detection eciency showed promising possibilities for neutron instrumentation

Pulse-reactor core monitoring with an innovative optical neutron detector

International audienceTo minimize uncertainty and strengthen estimation of energy deposited during power transients, we set up an online passive neutron ux measurement of a pulse reactor. Optical ssion chambers, are being developed in the framework of dependable neutron ux instrumentation for Sodium-cooled Fast Reactor (SFR) and Molten-Salt Reactor (MSR) of Generation IV by the French Atomic Energy and Alternative Energies Commission (CEA). Neutron interactions with a ssile layer coating release heavy-ions in the MeV-range, eventually leading to spontaneous photon emission in the ultraviolet to infrared range of the surrounding noble gas. Prototypes have previously been tested in an ideal pure neutron eld. In this paper, linearity of optical signal versus reactor power is assessed during startups and high power transients up to 21.6 GW. Excellent linearity results are obtained over 5 reactor power decades and detection remain possible over 7 decades. Detection range is only restrained by photodetector properties. Such detector may be routinely employed for high-dynamic transients monitoring by the core caisson of pulse reactors

SCENA: A simulation tool for radiation-induced gas scintillation

International audienceWithin the framework of the dependable neutron ux instrumentation development for Sodium-cooled Fast Reactor (SFR) of Generation IV, the French Alternative Energies and Atomic Energy Commission (CEA) is investigating an innovative technology based on optical signals produced within an ionization chamber. In such gaseous detectors, neutrons interact with a ssile material, releasing heavy ions in the MeV-range, eventually leading to spontaneous photon emission in the ultraviolet to infrared range. In this paper, the process of light generation is analyzed through a newly-developed computer code named SCENA. Semi-empirical models for ion-togas energy exchange and secondary electron production are assessed. The output of the SCENA subroutines are satisfactory checked against other electron swarm simulation tools, experimental data and a theoretical gas model. SCENA is able to follow the cold-plasma created along a heavy ion slowing-down in space and time evolution. This performance is a key point in the development of optical ionization chambers

Design of a high order Campbelling mode measurement system using open source hardware

International audienc

Development and first use of an experimental device for fission-induced spectrometry applied to neutron flux monitoring

International audienceIn order to provide dependable neutron flux instrumentation for Generation IV Sodium-cooled Fast Reactors (SFR), the French Atomic and Alternative Energies Commission (CEA) is investigating the feasibility of an innovative technology based on the optical signal produced within a fission chamber. In such gaseous detectors, neutrons interact with fissile material releasing heavy ions in the MeV-range, eventually leading to spontaneous photon emission in the ultraviolet-to-infrared range thanks to gas excitation and ionization. In this paper , the process of light generation is analyzed through semi-empirical models and custom-developed codes. A specific instrumentation has been defined and manufactured to emulate optical fission chambers and collect basic spectroscopic data required for model-based development approach. That testing device was named PSEG, which stands for Prototype of Scintillator Electrodes-Gas. Experimental validations have been carried out: the ionized argon gas exhibited no local thermodynamic equilibrium. Furthermore, the broadening of selected argon emission lines due to pressure change offers a promising self-diagnosis capability for future optical fission chambers