CNRS Université Bordeaux

Accueil du site > FRANCAIS > Pôle Santé-Environnement > Radioactivité & Environnement > Publications


Liste des publications depuis 2001.

Cliquer sur la couverture pour avoir accès au document (sous couvert d’autorisation).

Année 2019

GIF - 6.9 ko

Paleoclimate variations and impact on groundwater rechargein multi-layer aquifer systems using a multi-tracer approach (northernAquitaine basin, France)

Hydrogeology Journal, 27, 1439, 2019

M. Saltel, R. Rebeix, B. Thomas, M. Franceschi, B. Lavielle, P. Bertran

The northern Aquitaine basin (southwest France) is a large multi-layer aquifer system that contains groundwater with strong residence-time variability ranging from years to tens of thousands of years. This system constitutes an archive of paleoclimate variations. A multi-parameter approach involving isotopic tracers (14C, 18O, 2H) was used to determine the residence time of groundwater and to document climate fluctuations, while dissolved noble gases were used to estimate mean annual temperatures (noble gas recharge temperatures, NGRT) at the water table. Near-surface ground temperature reconstruction from 40 ka cal BP to the present was made using data collected from five aquifers. The coldest temperatures are recorded for late Marine Isotopic Stage (MIS) 3 and MIS 2, i.e. between 36 and 18 ka cal BP. The mean NGRT for the period 27–18 ka cal BP is estimated at 5.9 ± 0.9 °C, and a strong increase towards modern values (11–13 °C) is observed after 15 ka cal BP. The temperature change between the Holocene and the Last Glacial ranges from 5 to 7 °C, in agreement with previous NGRT studies in Europe. Since mean near-surface ground temperatures during the glacial were well above 0 °C, long-term presence of permafrost in northern Aquitaine is unlikely. However, a possible warm bias in reconstructed temperatures during the coldest events lies in the fact that NGRTs in cold regions do not reflect annual means but rather the ground temperature during the thaw months.

Uranium carbide oxidation from 873 K to 1173 K

Corrosion Science, 151, 44-56, 2019

C. Gasparrini, R. Podor, O. Fiquet, D. Horlait, S. May, M.R Wenman, W.E. Lee

Oxidation of UC was studied from 873 to 1173 K in air and in 10 Pa oxygen using a High Temperature Environmental SEM (HT-ESEM). Conversion to U3O8 improved when using 873 K as the oxide product was a fine powder. At higher temperatures (973 K to 1173 K) oxidation slowed due to a densification process with formation of coarse fragments. The oxide fragmentation at 973 K and 1073 K and oxide pulverisation at 873 K were observed in situ in a HT-ESEM. Cracking induced fragmentation and pulverisation was linked to stresses generated from the volumetric transformation from UC to U3O8.

Année 2018

GIF - 6.1 ko
Journal of Nuclear Materials

Durability of hot uniaxially pressed Synroc derivative wasteform for EURO-GANEX wastes

Journal of Nuclear Materials, 509, 43-53, 2018

Y.-H. Hsieh S.A Humphry-Baker, D. Horlaita, D.J. Gregg, E.R. Vance, W.E. Lee

A new titanate wasteform, Synroc-Z, was developed to contain minimal host phases for actinides and thus better suit the EURO-GANEX process. The processing conditions, waste loading and surface roughness were varied, and their effects on wasteform durability and microstructure were examined. Hot uniaxial pressing temperature was the most important factor in controlling density (<0.5 vol% porosity) and phase composition. Synroc-Z was found to have similar aqueous durability to Synroc-C. Leached samples formed Ti-oxide films and crystals on their surfaces as found by other researchers.

At low waste loadings (<20 wt%), Synroc-Z showed slightly poorer durability performance than Synroc-C owing to its greater perovskite content (30 vs. 20 wt% respectively). However, at 35 wt% waste loading, Synroc-Z maintained its durability performance. This result is explained by the higher volume fraction of buffer phase, rutile, which allows greater flexibility for waste loading.

GIF - 10.5 ko
Journal of the American Ceramic Society

Zirconium carbide oxidation : kinetics and oxygen diffusion through interface

Journal of the American Ceramic Society, 101, 2638-2652, 2018

C. Gasparrini, R. Chater D. Horlait, L Vandeperre, W.E. Lee

Oxidation of hot‐pressed ZrC was investigated in air in the 1073‐1373 K range. The kinetics were linear at 1073 K, whereas at higher temperature samples initially followed linear kinetics before undergoing rapid oxidation leading to a Maltese cross shape of the oxide. The linear kinetics at 1073 K was governed by inward oxygen diffusion through an intermediate layer of constant thickness between ZrC and ZrO2 which was comprised of amorphous carbon and ZrO2 nanocrystals. Diffusion of oxygen through the intermediate layer was measured to be 9 × 10−10 cm2 s−1 using 18O as a tracer in a double oxidation experiment in 16O/18O. Oxidation at 1073 and 1173 K produced samples made of m‐ZrO2 and either t‐ or c‐ZrO2 with an adherent intermediate layer made of amorphous carbon and ZrO2, whereas oxidation at 1273 and 1373 K produced samples with a voluminous oxide made of m‐ZrO2 showing a gap between ZrC and the oxide. A substoichiometric zirconia layer was found at the gap at 1273 K and no carbon uptake was detected in this layer when compared with the top oxide layer. The loss of the intermediate layer and the slowdown of the linear rate constant (g m−2 s−1) at 1273 K compared to 1173 K was correlated with the preferential oxidation of carbon at the intermediate layer which would leave as CO and/or CO2 leaving a gap between ZrC and substoichiometric zirconia.

Année 2017

JPEG - 9.1 ko

Soil prokaryotic communities in Chernobyl waste disposal trench T22 are modulated by organic matter and radionuclide contamination

FEMS Microbiology Ecology, 93 (8), 2017

N. Theodorakopoulos, L. Février, M. Barakat, P. Ortet, R. Christen, L. Piette, S. Levchuk, K. Beaugelin-Seiler, C. Sergeant, C. Berthomieu, V. Chapon

After the Chernobyl nuclear power plant accident in 1986, contaminated soils, vegetation from the Red Forest and other radioactive debris were buried within trenches. In this area, trench T22 has long been a pilot site for the study of radionuclide migration in soil. Here, we used 454 pyrosequencing of 16S rRNA genes to obtain a comprehensive view of the bacterial and archaeal diversity in soils collected inside and in the vicinity of the trench T22 and to investigate the impact of radioactive waste disposal on prokaryotic communities. A remarkably high abundance of Chloroflexi and AD3 was detected in all soil samples from this area. Our statistical analysis revealed profound changes in community composition at the phylum and OTUs levels and higher diversity in the trench soils as compared to the outside. Our results demonstrate that the total absorbed dose rate by cell and, to a lesser extent the organic matter content of the trench, are the principal variables influencing prokaryotic assemblages. We identified specific phylotypes affiliated to the phyla Crenarchaeota, Acidobacteria, AD3, Chloroflexi, Proteobacteria, Verrucomicrobia and WPS-2, which were unique for the trench soils.

GIF - 8.8 ko
Geological Society Special Publications Radioactive Waste Confinement : Clays in Natural and Engineered Barriers

Vertical distribution of helium and 40Ar/36Ar in porewaters of the Eastern Paris Basin (Bure/Haute-Marne) : constraints on transport processes through the sedimentary sequence

Geological Society Special Publications 443, 179-192, 2017

P. Jean-Bapiste, B. Lavielle, E. Fourre, T. Smith, M Pagel

As part of its ongoing project on repositories for high-activity, long-lived radioactive waste, a 2000 m deep borehole was drilled by the French Nuclear Waste Agency (ANDRA) in the layered structure of alternating aquifers and aquitards of the Eastern Paris Basin. Among the information retrieved from this borehole, the vertical distribution of chloride in porewaters showed that, in addition to vertical diffusion, lateral advection in the aquifers plays a major part in transporting chlorine away from the study area. Helium concentrations were also measured in porewaters along the borehole. Because the helium input function is different from that of chlorine, it represents an excellent alternative tracer to further constrain transport characteristics. We applied an advection–diffusion model to the helium profiles with the appropriate source term for 4He based on U–Th measured concentrations of uranium and thorium. 40Ar/36Ar data, which were available along the whole sequence, were also simulated. The modelled and measured 4He profiles were in good agreement, indicating that the transport parameters used for the chlorine simulations were robust. 40Ar/36Ar simulations also gave coherent results and confirmed that most of the radiogenic 40Ar remained trapped in the rocks (primarily in clays and feldspars).

Modelling solid solutions with cluster expansion, special quasirandom structures, and thermodynamic approaches

Applied Physics Review 4, 041301, 2017

V. Saltas, D. Horlait, E.N. Sgourou, F. Vallianatos, A. Chroneos

Modelling solid solutions is fundamental in understanding the properties of numerous materials which are important for a range of applications in various fields including nanoelectronics and energy materials such as fuel cells, nuclear materials, and batteries, as the systematic understanding throughout the composition range of solid solutions for a range of conditions can be challenging from an experimental viewpoint. The main motivation of this review is to contribute to the discussion in the community of the applicability of methods that constitute the investigation of solid solutions computationally tractable. This is important as computational modelling is required to calculate numerous defect properties and to act synergistically with experiment to understand these materials. This review will examine in detail two examples : silicon germanium alloys and MAX phase solid solutions. Silicon germanium alloys are technologically important in nanoelectronic devices and are also relevant considering the recent advances in ternary and quaternary groups IV and III-V semiconductor alloys. MAX phase solid solutions display a palette of ceramic and metallic properties and it is anticipated that via their tuning they can have applications ranging from nuclear to aerospace industries as well as being precursors for particular MXenes. In the final part, a brief summary assesses the limitations and possibilities of the methodologies discussed, whereas there is discussion on the future directions and examples of solid solution systems that should prove fruitful to consider.

GIF - 6.1 ko
Journal of Nuclear Materials

Oxidation of UC : An in situ high temperature environmental scanning electron microscopy study

Journal of Nuclear Materials, 494, 127-137, 2017

C. Gasparrini, R. Podor, D. Horlait, M.J.D. Rushton, O. Fiquet, W.E. Lee

In situ HT-ESEM oxidation of sintered UC fragments revealed the morphological changes occurring during the transformation between UC to UO2 and UO2 to U3O8 at 723–848 K and in an atmosphere of 10–100 Pa O2. Two main oxidation pathways were revealed. Oxidation at 723 K in atmospheres ≤25 Pa O2 showed the transformation from UC to UO2+x, as confirmed by post mortem HRTEM analysis. This oxidation pathway was comprised of three steps : (i) an induction period, where only surface UC particles oxidised, (ii) a sample area expansion accompanied by crack formation and propagation, (iii) a stabilisation of the total crack length inferring that crack propagation had stopped. Samples oxidised under 50 Pa O2 at 723 K and at 773–848 K for 10–100 Pa O2 showed an “explosive” oxidation pathway : (i) sample area expansion occurred as soon as oxygen was inserted into the chamber and crack propagation and crack length followed an exponential law ; (ii) cracks propagated as a network and the oxide layer fragmented, (iii) an “explosion” occurred causing a popcorn-like transformation, typical for oxidation from UO2 to U3O8. HRTEM characterisation revealed U3O8 preferentially grow in the [001] direction. The explosive growth, triggered by ignition of UC, proceeded as a self-propagating high-temperature synthesis reaction, with a propagation speed of 150–500 ± 50 μm/s.

JPEG - 7.4 ko
Oxidation of Metals

Zirconium carbide oxidation : Maltese cross formation and interface characterization

Oxidation of Metals, 88, 509-519, 2017

C. Gasparrini, R. Podor, D. Horlait, R. Chater, W.E. Lee

Oxidation of dense hot-pressed ZrC specimens from 1073 to 1473 K was investigated using an in situ technique : HT-ESEM. Cuboid specimens were monitored on the surface and on edges and corners during oxidation in order to understand the influence of crack formation and propagation on the Maltese cross shape development of the oxide. The oxidation mechanism comprised three steps : (1) delamination of sample edges, (2) crack formation at corners and (3) crack propagation towards the inner core and formation of microcracks parallel to the interface that increase the accessible surface area followed by a drastic volume expansion. The microcrack pattern is found to be repetitive as if a cyclic debonding of the interface occurred. Characterization of the interface by TEM and HRTEM revealed the interface between ZrC and ZrO2 to comprise a 2 µm thick amorphous carbon matrix with ZrO2 nanocrystals embedded in it.

GIF - 10.5 ko
Journal of the American Ceramic Society

Synthesis and physical properties of (Zr1−x,Tix)3AlC2 MAX phases

Journal of the American Ceramic Society,100, 3393-3401, 2017

E. Zapata-Solvas, M.A. Hadi, D. Horlait, D.C. Parfitt, A. Thibaud, A. Chroneos, W.E. Lee

MAX phase solid solutions physical and mechanical properties may be tuned via changes in composition, giving them a range of possible technical applications. In the present study, we extend the MAX phase family by synthesizing (Zr1−xTix)3AlC2 quaternary MAX phases and investigating their mechanical properties using density functional theory (DFT). The experimentally determined lattice parameters are in good agreement with the lattice parameters derived by DFT and deviate <0.5% from Vegard’s law. Ti3AlC2 has a higher Vickers hardness as compared to Zr3AlC2, in agreement with the available experimental data.

GIF - 10.5 ko
Journal of the American Ceramic Society

Experimental synthesis and density functional theory investigation of radiation tolerance of Zr3(Al1-xSix)C2 MAX phases

Journal of the American Ceramic Society, 100, 1377-1387, 2017

E. Zapata-Solvas, S.R.G. Christopoulos, N. Ni, D.C. Parfitt, D. Horlait, M.E. Fitzpatrick, A. Chroneos, W.E. Lee

Synthesis, characterization and density functional theory calculations have been combined to examine the formation of the Zr3(Al1–xSix)C2 quaternary MAX phases and the intrinsic defect processes in Zr3AlC2 and Zr3SiC2. The MAX phase family is extended by demonstrating that Zr3(Al1–xSix)C2, and particularly compositions with x≈0.1, can be formed leading here to a yield of 59 wt%. It has been found that Zr3AlC2 - and by extension Zr3(Al1–xSix)C2 - formation rates benefit from the presence of traces of Si in the reactant mix, presumably through the in situ formation of ZrySiz phase(s) acting as a nucleation substrate for the MAX phase. To investigate the radiation tolerance of Zr3(Al1–xSix)C2, we have also considered the intrinsic defect properties of the end-members. A-element Frenkel reaction for both Zr3AlC2 (1.71 eV) and Zr3SiC2 (1.41 eV) phases are the lowest energy defect reactions. For comparison we consider the defect processes in Ti3AlC2 and Ti3SiC2 phases. It is concluded that Zr3AlC2 and Ti3AlC2 MAX phases are more radiation tolerant than Zr3SiC2 and Ti3SiC2, respectively. Their applicability as cladding materials for nuclear fuel is discussed.

JPEG - 10.9 ko
Materials Research Letters

Experimental and DFT investigations of (Cr,Ti)3AlC2 solid solution stability

Materials Research Letters, 5, 144-157, 2017

P.A Burr, D. Horlait, W.E. Lee

Using a synergistic combination of experimental and computational methods, we shed light on the unusual solubility of (Cr,Ti)3AlC2 MAX phase, showing that it may accommodate Cr only at very low concentrations (<2 at%) or at the exact Cr/(Cr + Ti) ratio of 2/3, even when the ratio of reactants is far from this stoichiometry (1/2 ≤ Cr/(Cr + Ti) ≤ 5/6). In both phases, Cr exclusively occupies the 4f sites, bridging carbide layers with the Al layer. Despite this, the peculiar stability of (Cr2/3Ti1/3)3AlC2 is attributed to the formation of strong, spin-polarized Cr–C bonds, which result in volume reduction and a marked increase in c/a ratio.

Année 2016

GIF - 8 ko
Journal of Mass Spectrometry

Development towards a double focusing isotopic separator for noble gas isotope enrichment

Journal of Mass Spectrometry, 51, 718-723, 2016

B. Lavielle, B. Thomas, E. Gilabert, G. Canchel, D. Horlait, S. Topin, F. Pointurier, C. Moulin

A double focusing sector field mass filter used in Nier–Johnson geometry has been built in order to perform Kr isotope enrichment for 81Kr and 85Kr isotopes. The principle consists in implanting Kr+ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr+ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (1015 to 1016 atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer.

JPEG - 10.9 ko
Journal of Analytical Atomic Spectrometry

Ultratrace analysis of krypton isotopes by resonant ionization spectroscopy-time of flight mass spectrometry (RIS-TOF).

Journal of Analytical Atomic Spectrometry, 31(4), 994-1001, 2016

E. Gilabert, B. Lavielle, B. Thomas, S. Topin, F. Pointurier, C. Moulin

A new RIS-TOF instrument, called FAKIR (Facility for Analyzing Krypton Isotope Ratios), has been developed at CENBG in order to measure Kr isotope ratios with an extremely high sensitivity. The instrument uses a single color Kr ionization scheme with tunable coherent UV photons near 216.6 nm. A two-photon resonance excitation allows it to reach the 5p[5/2]2 excitation level followed by a single-photon ionization. Krypton ions are accelerated towards an electron multiplier. The instrument includes a cryogenic concentrator that increases the efficiency of the ion source and a new selecting system allowing the deflection of the abundant isotopes before they impact the detector. This device eliminates the blinding effect on the detector that alters the detection of the less abundant Kr isotopes. The current sensitivity of the instrument of ∼6700 atoms has been demonstrated by extracting the gas from 37 mg of the Boguslavka iron meteorite. The associated errors on the 81Kr isotope ratio measurements did not exceed ∼12%. A good agreement is observed with conventional mass spectrometry analysis, which requires several grams of material, by measuring the cosmic ray exposure age of the Boguslavka meteorite.

GIF - 13.5 ko
Nuclear Instruments and Methods in Physics Research Section B

Implantation damage in heavy gas implanted 4H-SiC

Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms, 374, 71-75, 2016

C. Jiang, J. Nicolaï, A. Declémy, E. Gilabert, M.-F. Beaufort, J.-F. Barbot

Single crystals of SiC were implanted with heavy inert gases (Xe, Ar) at elevated temperatures (300–800 °C) and for a large range of fluence (1 × 1012–1 × 1015 ions cm−2). Thermodesorption measurements suggest that gas is trapped by implantation-induced vacancy-type defects impeding any gas diffusion. The damage accumulation versus dose was studied through the tensile elastic strain determined by using X-ray diffraction. Results show that at low dose the strain is predictable via a thermally activated direct impact model. The low thermal activation energy at saturation suggests a dynamic recovery process dominated by the migration of interstitial-type defects as its relaxation during post thermal annealing. As compared with light-gas implantation the heavy-gas to defect ratio is low enhancing the formation of strongly perturbed zones rather than the formation of bubble precursors.

GIF - 14.2 ko
Journal of the European Ceramic Society

Dilatometric study of a co-converted (U,Am)O2 powder

Journal of the European Ceramic Society, 36, 1775-1782, 2016

L. Ramond, D. Horlait, T. Delahaye, G. Jouan, A. Gauthé, B. Arab-Chapelet, S. Picart

A possible option to reduce the radiotoxicity of nuclear waste is to transmute minor actinides and notably americium into lighter short-lived elements in fast neutron reactors of fourth generation. It consists in irradiating uranium–americium mixed-oxide compounds named AmBB (Americium-Bearing Blankets) and located at the reactor core periphery. Among the processes developed to fabricate AmBB, a chemical synthesis route was investigated. Dense samples were achieved using a simplified pelletizing-sintering process from oxalate co-converted powder. This work focuses on the identification and comprehension of the steps occurring during the sintering of these co-converted (U,Am)O2 powders. To discriminate the different phenomena observed by dilatometric measurements, different experimental techniques were performed. It allowed identifying that the sintering of the finest particles occurred in the [1000–1350 K] range while the elimination of porosity and sintering of (U,Am)O2 larger grains is realized in the [1400–1900 K] range with an apparent activation energy of 430 kJ.mol−1.

Année 2015

GIF - 22.4 ko
Journal of Hazardous Materials

Use of combined microscopic and spectroscopic techniques to reveal interactions between uranium and Microbacterium sp. A9, a strain isolated from the Chernobyl exclusion zone

Journal of Hazardous Material, 285, 285-293, 2015

N. Theodorakopoulos, V. Chapon F. Coppin, M. Floriani, T. Vercouter, C. Sergeant, V. Camillieri, C. Berthomieu, L. Fevrier.

Although uranium (U) is naturally found in the environment, soil remediation programs will become increasingly important in light of certain human activities. This work aimed to identify U(VI) detoxification mechanisms employed by a bacteria strain isolated from a Chernobyl soil sample, and to distinguish its active from passive mechanisms of interaction. The ability of the Microbacterium sp. A9 strain to remove U(VI) from aqueous solutions at 4 °C and 25 °C was evaluated, as well as its survival capacity upon U(VI) exposure. The subcellular localisation of U was determined by TEM/EDX microscopy, while functional groups involved in the interaction with U were further evaluated by FTIR ; finally, the speciation of U was analysed by TRLFS. We have revealed, for the first time, an active mechanism promoting metal efflux from the cells, during the early steps following U(VI) exposure at 25 °C. The Microbacterium sp. A9 strain also stores U intracellularly, as needle-like structures that have been identified as an autunite group mineral. Taken together, our results demonstrate that this strain exhibits a high U(VI) tolerance based on multiple detoxification mechanisms. These findings support the potential role of the genus Microbacterium in the remediation of aqueous environments contaminated with U(VI) under aerobic conditions.

Année 2014

GIF - 13.5 ko
Nuclear Instruments and Methods in Physics Research Section B

Helium behaviour in UO2 through low fluence ion implantation studies

Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms, 327, 113-116, 2014

P. Garcia, E. Gilabert, G. Martin, G. Carlot, C. Sabathier, T. Sauvage, P. Desgardin, M.-F. Barthe

In this work we focus on experiments involving implantation of 500 keV 3He ions in sintered polycrystalline material. Samples are implanted at low fluences (∼2 ×1013 ions/cm2) and subsequently isothermally annealed in a highly sensitive thermal desorption spectrometry (TDS) device PIAGARA (Plateforme Interdisciplinaire pour l’Analyse des GAz Rares en Aquitaine). The helium fluencies studied are two to three orders of magnitude lower than previous Nuclear Reaction Analysis (NRA) experiments carried out on identical samples implanted at identical energies. The fractional release of helium obtained in the TDS experiments is interpreted using a three-dimensional axisymmetric diffusion model which enables results to be quantitatively compared to previous NRA data. The analysis shows that helium behaviour is qualitatively independent of ion fluency over three orders of magnitude : helium diffusion appears to be strongly inhibited below 1273 K within the centre of the grains presumably as a result of helium bubble precipitation. The scenario involving diffusion at grain boundaries and in regions adjacent to them observed at higher fluencies is quantitatively confirmed at much lower doses. The main difference lies in the average width of the region in which uninhibited diffusion occurs.

GIF - 14.2 ko
Journal of the European Ceramic Society

Helium behaviour in stoichiometric and hyper-stoichiometric UO2

Journal of the European Ceramic Society, 34(5), 1265-1277, 2014

Z. Talip, T. Wiss, E.-A. Maugeri, J.-Y. Colle, P.-E. Raison, E. Gilabert, M. Ernstberger, D. Staicu, R.J.M. Konings

Understanding the long-term behaviour of the UO2 spent fuel in terms of helium build-up and oxidation is a very important issue for safety aspects of storage and disposal. Although helium behaviour in stoichiometric UO2 has been studied by many authors, it has not been well established and there is a lack of experimental studies in non-stoichiometric UO2. In this study, an infusion technique was chosen to introduce helium in stoichiometric and hyperstoichiometric single and polycrystalline UO2 and polycrystalline U3O8 samples. Characterization of the samples before and after infusion and after thermal desorption measurements were performed by thermogravimetry, X-ray diffraction, laser flash technique and scanning electron microscopy. It was observed that the increase of stoichiometry in UO2 affects barely the dissolved helium quantity (under the same infusion conditions as in stoichiometric), while it has a more pronounced influence on the helium diffusion. These two effects are much more pronounced for U3O8.

Année 2013

GIF - 9.8 ko
Engineering Geology

Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, mont terri underground rock laboratory

Engineering Geology, 156, 46-57, 2013

A. Maineult, B. Thomas, C. Nussbaum, K. Wieczorek, D. Gibert, B. Lavielle, B. Kergosien, F. Nicollin, K. Mahiouz, N. Lesparre

Before the excavation of the new gallery Ga08 in the Mont Terri Underground Rock Laboratory (Switzerland), which joined the existing gallery Ga04 in 2008, the end-face of gallery Ga04 was instrumented in 2007 to characterize the evolution of the rock mass with geochemical and geophysical methods. The noble gas content of a 12-m long horizontal borehole evidenced that desaturation processes occurred in the first 2 m, where pre-existing fractures accommodated the stress change during excavation of gallery Ga04 four years before. These first 2 m are associated with the so-called Excavation Damaged Zone (EDZ). As an inflow of pore water was observed in this borehole few weeks after its drilling, continuous self-potential (SP) measurements were performed to characterize its dynamics. After the drilling of new sub-horizontal boreholes in the end-face, strong localized variations of SP occurred. The comparison with the geological features of the rock mass suggests that these dynamic anomalies have to be associated with fluid circulation in pre-existing tectonic fractures that were primarily reactivated by the excavation of the gallery Ga04 and subsequently by the drilling operations.

GIF - 2.8 ko
Journal of Nuclear Materials

Helium interaction with vacancy-type defects created in silicon carbide single crystal

Journal of Nuclear Materials, 436, 150-157, 2013

F. Linez, E. Gilabert, A. Debelle, P. Desgardin, M.-F. Barthe

Generation of He bubbles or cavities in silicon carbide is an important issue for the use of this material in nuclear and electronic applications. To understand the mechanisms prior to the growth of these structures, an atomic-scale study has been conducted. 6H–SiC single crystals have been implanted with 50 keV-He ions at 2 × 1014 and 1015 cm−2 and successively annealed at various temperatures from 150 to 1400 °C. After each annealing, the defect distributions in the samples have been probed by positron annihilation spectroscopy. Four main evolution stages have been evidenced for the two investigated implantation fluences : at (1) 400 °C for both fluences, (2) at 850 °C for the low fluence and 950 °C for the high one, (3) at 950 °C for the low fluence and 1050 °C for the high one and (4) at 1300 °C for both fluences. The perfect correlation between the positron annihilation spectroscopy and the thermodesorption measurements has highlighted the He involvement in the first two stages corresponding respectively to its trapping by irradiation-induced divacancies and the detrapping from various vacancy-type defects generated by agglomeration processes.

JPEG - 7.3 ko
American Journal of Hematology

Iron homeostasis in pathological retina : transferrin as new therapeutic agent

American Journal of Hematology, 88(5), E167-E168, 2013

E. Picard, M.H. Vesvres, C. Sergeant, M. Berdugo, M. El Sanharawi, J.C. Jeanny

Background : Iron is an essential metabolic component for enzymes specifically required for the vision mechanisms. Most of the proteins involved in iron homeostasis have been recently described and localized in the retina. Retinal degeneration has been associated with iron accumulation in age-related macular degeneration (AMD), in several rodent models which had one or several iron regulating proteins impairment or associated with genetic vision defects. To prevent iron accumulation derived damages, we tested the potential neuroprotective effect of human transferrin (hTf) on the photoreceptors (PRs) degeneration in genetic or experimentally induced models. Materiels and Methods : Eyes from rd10 mice and RCS rats at different stages of photoreceptors degeneration were collected and analyzed by PIXE method for iron contents determination in retina. We intraperitoneally injected human transferrin (hTf) in 5-day-old rd10 mice up to 25 days. To constitutively express hTf in rd10 mice, we have crossbred rd10 mice with transgenic mice for human transferrin (rd10/hTf). We have used intense white LED light on rats to induce retinal degeneration, and intravitreally injected hTf just before exposure. We observed retinal functions in vivo by optical coherence tomography and by electroretinography and compared PRs preservation by measurement of the outer nuclear layer thickness on histological sections. Results : We demonstrated an iron accumulation in PRs segments concomitant with retinal degeneration stages in rd10 mice and RCS rats. At the peak of PRs degeneration, rd10/hTf mice showed less PRs death than rd10 mice. Intraperitoneal injection of hTf in rd10 mice resulted in major PRs preservation. In rats, HTf intravitreal injection decreased oxidative stress and iron accumulation, both resulting from illumination. PRs were protected and theirs physiological functions are preserved. Conclusion : Tf injected in systemic or directly into the eye, has a potent protective effect on the neurodenegerative process. This effect seems to be due to the iron chelating effect of Tf. This study highlights the therapeutical potential of Tf in retinal diseases associated with iron accumulation such as aging or AMD. Control of iron impairment in tissues could be corrected by adjusting Tf level by different molecular or pharmacological strategies. .

Année 2012

JPEG - 5.4 ko
Applied Geochemistry

Microbial diversity in contaminated soils along the T22 trench of the Chernobyl experimental platform

Applied Geochemistry, 27 (7), 1375-83, 2012

V. Chapon, L. Piette, M.-H. Vesvres, F. Coppin, C. Le Marrec, R. Christen, N . Theodorakopoulos, L. Fevrier, S. Levchuk, A. Martin-Garin, C. Berthomieu, C. Sergeant

The diversity of bacterial communities exposed to radioactive contamination in Chernobyl soils was examined by a combination of molecular and culture-based approaches. A set of six radioactive soil sam- ples, exhibiting high levels of 137Cs contamination, were collected from the T22 trench. Three samples were also collected in nearby soils with low contamination. Complex bacterial community structures were observed in both highly and weakly contaminated samples, using a molecular approach targeting the 16S rRNA gene. However, the presence of specific populations within samples from highly contaminated soils could not be revealed by statistical analysis of the DGGE profiles. More than 200 culturable isolates, representative of dominant morphotypes, were grouped into 83 Operational Taxonomic Units (OTUs) and affiliated to Firmicutes, Actinobacteria, Alpha-, Beta-, Gamma-Proteobacteria and Bacteroïdetes. No specific pattern linked to contamination was observed for these culturable bacteria. The results show that both highly and weakly contaminated soils host a wide diversity of bacteria, suggesting that long term exposure to radionuclides does not lead to the extinction of bacterial diversity. .

JPEG - 5.4 ko
Applied Geochemistry

Stages of evolution of a Toarcian compacted claystone around galleries excavated between 1 and 124 years ago by the study of noble gases dissolved in pore water at the Tournemire Underground Research Laboratory (France)

Applied Geochemistry, 27 (7), 1403–1416, 2012

Bernard Lavielle, Jean-Michel Matray, Bertrand Thomas, Alexandre Dauzères, Fethi Bensenouci, Eric Gilabert

The purpose of this work is to study the diffusion properties in an argillaceous formation and how these properties change after the excavation of galleries, over a long period. The Tournemire Underground Research Laboratory (URL) located in Aveyron (France) offers the unique opportunity to investigate different stages of the evolution of the so-called Excavation Damaged Zone (EDZ) over a period of about 124 a. Four horizontal boreholes parallel to the bedding and one vertical borehole were drilled in order to study diffusion transport in the EDZ in both directions in galleries excavated 124, 13, 6, and 1 a ago, respectively. Noble gases dissolved in the pore water of 47 core samples were extracted in order to establish precise depth profiles. Mainly produced in situ by decay of U and Th, radiogenic He accumulates in the pore water of rocks and escapes toward the gallery, allowing a characterization of the diffusive transport in the EDZ and its evolution with time. For the oldest gallery (1882–1888), core mapping reveals an EDZ well developed with fractures up to a depth of 1.8 m. In this zone, all radiogenic He has been lost and at the same time heavy noble gases are trapped in the rock with an enrichment of Xe relative to Kr and of Kr relative to Ar. From 1.8 m, He concentration increases with depth to reach a plateau at about 3.5 m corresponding to a concentration normally found in the unaltered zone. Considering diffusive transport of the radiogenic He to the EDZ, model calculations allowed proposing transport properties in the unfractured and undisturbed zone (UZ) with a pore diffusion coefficient Dp of 1x10[-10] m2/s deduced from the best-fit curve to experimental data and a mean porosity of 0.1 obtained form petrophysical measurements. The most recent gallery (2008) did not show any evidence of EDZ at depths greater than 7.5 cm. A fracture located around 0.75 m, possibly of tectonic origin, induced large advection and diffusion losses of He on both sides in the next 50 cm. Excesses of Ar, Kr and Xe are found, suggesting diffusion of air from the gallery associated with He losses. The 6-a-old gallery is clearly influenced by fractures of tectonic origin increasing the EDZ thickness of 0.7 m up to a Damaged Zone of 1.8 m. Based on the He concentration profile, the 13-a-old gallery (1996) has a net EDZ of 1.2 m, larger than the 0.7 m deduced from the structural analysis by core mapping, followed by a disturbed zone of up to 3.5 m that could represent an intermediate stage before the development of fractures in the EDZ. The vertical borehole drilled in the same gallery shows a less extensive damaged zone (1.4 m) and allows the determination of a Dp of 3x10[-11] m2/s taking into account the anisotropy relative to the stratification plane. The rare gas analysis has, therefore, enabled confirmation and better description of the net time-dependent evolution of the EDZ around drifts in the argillaceous Tournemire site : no obvious EDZ for the 1-a gallery (2008), 1.2 m width for the 13-a-old gallery (1996), and 2 m width for the century-old tunnel. The occurrence of a disturbed and unfractured zone (dZ) around the 13-a-old gallery undetected by structural studies and geophysical methods clearly demonstrates the power of radiogenic He in assessing the transport properties around drifts excavated at different ages in compacted clay rocks.

GIF - 12.1 ko
Journal of Environmental Radioactivity

Evidence of 131I and 134,137Cs activities in Bordeaux, France due to the Fukushima nuclear accident

Journal of Environmental Radioactivity, Vol. 114, p.61, 2012

F. Perrot, Ph. Hubert, Ch. Marquet, M.S. Pravikoff, P. Bourquin, H. Chiron, P.-Y. Guernion, A. Nachab

Following the Fukushima nuclear accident, low-background gamma spectrometry measurements were performed with HPGe detectors at the PRISNA platform located at the CENBG laboratory in Bordeaux, France. Different kinds of samples were collected and measured between March 26 and May 14, 2011. The first fission product observed was 131I with maximum activity values of 2.4 mBq/m3 in atmospheric dusts in air, 3.5 Bq/L in rain water, 15 Bq/kg in grass and 0.9 Bq/L in cow milk. The 134,137Cs isotopes were also detected in air and in grass at a maximum level of 0.2 mBq/m3 and 0.7 Bq/kg respectively, around one order of magnitude less than 131I activity, but they were below detection limits in the other samples. All these activity values were consistent with others measured in France by IRSN and were well below those reported in May 1986 after the Chernobyl accident.

Année 2011

GIF - 4.6 ko
Geochimica & Cosmochimica Acta

Contribution of logging tools to understanding helium porewater data across the mesozoic sequence of the east of the Paris basin

Geochimica & Cosmochimica Acta, 75(23), 7566-7584, 2011

A. Battani, T. Smith, J.C. Robinet, J. Brulhet, B. Lavielle, D. Coelho

Helium concentration measurements made on water and rock samples collected at various depths along a 2000 m depth borehole drilled in the eastern part of the Paris basin and reaching the Triassic conglomerates were used to establish a vertical profile of dissolved helium concentration throughout the entire Mesozoic sedimentary pile. Wireline logging tools were used to measure rock density, porosity and U and Th contents every 15 cm in the various formations. Samples from the deepest Muschelkalk and Buntsandstein show a very good agreement between measured and calculated 4He porewater contents. Shallower levels show lower and lower 4He concentrations compared to calculated values when going upwards. The data set obtained by wireline logging measurements was used as inputs for numerical simulations of 1D He production/diffusion throughout the 2000 m profile. Several assumptions regarding the transport properties in the various sedimentary layers were tested and all were found to yield fairly good agreement between modeled and measured He concentrations. There is no need to invoke either a transient regime or a deep crustal He flux in this “quiet” (seismically inactive) part of the Paris basin. Moreover, the modeling results suggest that the Keuper massive halite level associated with the upper Muschelkalk pre-evaporitic series efficiently isolates the overlying layers from any input from deeper formations in the Meuse/Haute Marne area.

GIF - 11.9 ko
Physics and Chemistry of the Earth

Dissolved helium distribution in the oxfordian and dogger deep aquifers of the Meuse/Haute-marne area

Physics and Chemistry of the Earth, 36(17-18), 1511-1520, 2011

E. Fourré, P. Jean-Baptiste, A. Dapoigny, B. Lavielle, T. Smith, B. Thomas, A. Vinsot

The 140-m-thick, clay-rich Callovo-Oxfordian (COX) layer of the eastern Paris Basin, France, is being considered by the French Nuclear Waste Agency (Andra) as a long-term underground nuclear waste repository. Andra has selected a 250 km2 area (transposition zone) to be further characterised, especially in view of the confinement properties exhibited by the COX. This study reports the helium concentrations and isotopic ratios of water samples from the aquifers above and below the COX, which are the Oxfordian and Dogger aquifers, respectively. The samples were collected from five drilling sites (2007–2008). Both the Oxfordian and Dogger groundwaters are of meteoric origin and have accumulated radiogenic He with a 3He/4He ratio of approximately 0.02 Ra. The He concentrations in the groundwaters are two orders of magnitude higher than in the air-saturated water in the Oxfordian and approximately 10 times higher in the Dogger than in the Oxfordian. One borehole was drilled down into the Triassic sediments, allowing a sample to be collected from the Bundsandstein aquifer. Here, the He concentration is of the same order of magnitude as those measured in the Dogger, but the isotopic ratio is slightly higher at 0.04 Ra. However, this ratio is approximately 10 times lower than those measured by Marty et al. (2003) in waters collected closer to the Trias recharge and tagged with mantle-derived He. This lower ratio is most likely due to a significant and rapid slowdown of the circulation in this aquifer, allowing substantial radiogenic He accumulation. A key conclusion of this study concerns the lateral non-homogeneity of the studied area : He concentrations are higher in the northern part of the transposition zone. This observation can be explained by a longer residence time of the waters and/or a higher input of He from the basement. A simplified 2D model of He transport shows that the second hypothesis alone does not allow fitting of the data, thus implying more stagnant water in this area. The indicative residence times derived from this coarse model are 0.3–0.5 Myr (Oxfordian) and 0.5–0.6 Myr (Dogger) for the borehole located in the centre of the investigated zone ; for the northernmost borehole, they reach 0.8–1.4 Myr for the Oxfordian and 1.5 Myr for the Dogger.

GIF - 11.9 ko
Physics and Chemistry of the Earth

A profile of helium-4 concentration in pore-water for assessing the transport phenomena through an argillaceous formation (Tournemire, France)

Physics and Chemistry of the Earth, 36(17-18), 1521-1530, 2011

F. Bensenouci, J.L. Michelot, J.M. Matray, S. Savoye, B. Lavielle, B. Thomas, P. Dick

A vertical distribution of helium-4 was obtained in pore-water from the Toarcian/Domerian argillaceous formation at Tournemire (South Aveyron, France). Most of the studied core samples were collected from two vertical air-drilled boreholes across the impervious argillaceous formation and penetrating the bounding aquifers. Accessible porosities for helium were assumed similar to those of water and calculated by weighting before and after heating the core samples. Helium-4 concentrations were obtained after out-gassing the rock samples in tight containers. The comparison of the total amount of 4He produced since the deposition of the formation with that presently measured in the rock reveals that more than 97% of 4He has been lost from the solid phase to pore-water and afterwards to the surrounding aquifers. Helium distribution in pore water shows a complex profile because of the presence of unexpectedly 4He-rich samples in the lower part of the Upper Toarcian level. In order to understand this distribution and to assess the transport of helium at the formation scale, a series of preliminary model calculations were performed using helium diffusion coefficients three times higher than those of water isotopes. The comparison between simulated and experimental data indicates that : (1) the helium profile could be similar to those of deuterium and chloride in pore-water if some unexpectedly 4He-rich samples are not considered ; (2) the estimated transport parameters (at small scale) may be transposable at the formation scale with some uncertainties ; (3) a steady state has most probably been reached between the in situ helium production and its loss towards the aquifers ; (4) only 17–30 Ma of diffusion time would be necessary to obtain steady state ; this is short compared to the formation age (180 Ma) and thus the helium profile cannot give very precise information about diffusion time in the massif, but is in agreement with the hypothesis that transport processes are dominated by diffusion.

Biogeochemical processes in a clay formation in situ experiment : Part D- Microbial analyses - Synthesis of results

Applied Geochemistry, 26, 980-989, 2011

S. Stroes-Gascoyne, C. Sergeant, A. Schippers, C.J. Hamon, S. Nèble, M.-H. Vesvres, V. Barsotti, S. Poulain, C. Le Marrec

The purpose of the Porewater Chemistry (PC) experiment at the Mont Terri (MT) Underground Rock Laboratory (URL) was to measure geochemical parameters, such as pH, Eh and pCO2, in the porewater of the Opalinus Clay formation. Although the PC experiment was designed and implemented carefully from a geochemical perspective, conditions were not sterile and some microbial and nutrient contamination likely occurred. Microbial activity in the added synthetic porewater in the borehole was apparent shortly after initiation of the experiment and affected the geochemical parameters observed in the porewater. This paper summarizes the results from microbial analyses of post-termination PC water and overcore clay samples, conducted to attempt to elucidate the role of microbial activity in the evolution of the geochemical conditions in the PC experiment. Microbial analyses of the PC borehole water, and of clay overcore samples from around the borehole, were carried out at three laboratories and included both molecular biology and culturing methods. Results indicated the presence of heterotrophic aerobic and anaerobic organisms that resulted likely from the initial, non-sterile conditions, sustained by suspected contamination with organic matter (glycerol, acetone). The results also indicated the presence of nitrate-reducers, iron-reducers, sulphate-reducers and methanogens (i.e., Bacteria as well as Archaea), suggesting a reducing environment with Fe(III)- and sulphate reduction and methanogenesis occurring in the PC water and adjacent clay. A black precipitate containing pyrite (identified by XRD and SEM) and a strong H2S smell in the porewater confirmed the occurrence of sulphate reduction. Microorganisms identified in the porewater included Pseudomonas stutzeri, Bacillus licheniformis, Desulfosporosinus spp. and Hyphomonas spp. Species identified in enrichment cultures from the overcore samples included Pseudomonas stutzeri, three species of Trichococcus spp., Caldanaerocella colombiensis, Geosporobacter subterrenus and Desulfosporosinus lacus. Overall the results indicated a thriving microbial community in the PC water and adjacent clay in contrast to “undisturbed” Opalinus Clay for which limited evidence for a small viable microbial community was given in a previous study (Poulain et al. 2008 Geomicrobiol. J. 25(5) : 240- 249 ; Stroes-Gascoyne et al. 2007 Geomicrobiol. J. 24, 1-17 ; Mauclaire et al. 2007 Physics and Chemistry of the Earth 32, 232-240).


Année 2010

Human transferring expressed in transgenic Rd10 mice or ip injected Rd10 mice protects retinal photoreceptors degeneration

Molecular Vision, 16, 2612-25, 2010

E. Picard, L. Jonet, C. Sergeant, M.H. Vesvres, F. Behar-Cohen, Y. Courtois, J.C. Jeanny


GIF - 1.7 ko
Applied Geochemistry

Establishing constraints on groundwater ages with 36Cl, 14C, 3H, and noble gases : A case study in the eastern Paris basin, France

Applied Geochemistry, Volume 25, Issue 1, January 2010, Pages 123-142

ErratumApplied Geochemistry, Volume 25, Issue 7, July 2010, Pages 1092-1093

Véronique Lavastre, Corinne Le Gal La Salle, Jean-Luc Michelot, Sophie Giannesini, Lucilla Benedetti, Joël Lancelot, Bernard Lavielle, Marc Massault, Bertrand Thomas, Eric Gilabert, Didier Bourlès, Norbert Clauer, Pierre Agrinier

Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using 3H, 14C and 36Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses.

Année 2009

GIF - 2.8 ko
Journal of Nuclear Materials

Behaviour of helium after implantation in molybdenum

J. Nucl. Mat. 385 (2009) 294-298

C. Viaud, S. Maillard, G. Carlot, C. Valot, E. Gilabert, T. Sauvage, C. Peaucelle and N. Moncoffre

This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.


GIF - 4.5 ko
Comptes Rendus Physique

Radioactivity measurements applied to the dating and authentication of old wines

Comptes Rendus Physique, Volume 10, Issue 7, September 2009, Pages 622-629

Ph. Hubert, F. Perrot, J. Gaye, B. Médina, M.S. Pravikoff

For many years the neutrino group in the CENBG has been involved in the development of low background γ -ray spectrometers, based on the use of HPGe crystals. When applied to radioactivity measurements of wine in bottles, it has been shown that besides the well-known isotope 40K, the wine contains also trace amounts of 137Cs (less than 1 Bq/l) with an activity depending on the vintage. This technique has thus led to the possibility to date the wine bottles of vintages between 1952 and ∼1980 and to verify the year written on the label or on the cork. Since the measurements do not require opening the bottle, the technique has also proved to be very useful for detecting counterfeit wines of the XIXth century and first half of the XXth century.


Tchernobyl : des bordelaises cherchent à identifier des bactéries résistantes à la radioactivité (article grand public)

H20 : la revue des Sciences et de l’Industrie en Aquitaine, 95, 2009 (et) Site WEB de Cap Sciences Bordeaux

A. Marsat (journaliste), C. Sergeant, C. Le Marrec



Quand des bactéries vivent en conditions extrêmes…

Signet Visage des Sciences (Fête de la Science 2009)

C. Sergeant

On sait maintenant que la vie peut se développer dans des conditions très variées, y compris extrêmes (très fortes températures : plus de 110°C ; très fortes pressions : à plus de 4000 m sous la mer ; en présence de très peu d’eau et même dans un milieu très radioactif). C’est à la découverte et à l’étude du métabolisme de ce type de bactéries que l’équipe de Claire Sergeant s’intéresse. Ainsi, elle a pu mettre en évidence deux espècesde bactéries jusque là inconnues, dans une argile très ancienne et très compacte étudiée dans le cadre des recherches sur le stockage des déchets radioactifs. Les expériences en cours sur les populations bactériennes de sols de régions proches de Tchernobyl, contaminés par des radioéléments, vont permettre de mieux comprendre les mécanismes qui leur permettent de s’adapter à ces conditions inhospitaières et pourraient mener à la découverte de souches bactériennes utilisables .



Année 2008

JPEG - 8.5 ko
Meteoritics & Planetary Science

The complex exposure histories of the Pitts and Horse Creeck iron meteorites : implications for meteorite delivery models

Meteoritics & Planetary Science, vol. 43, Issue 8, p.1321-1332

K. C. Welten, K. Nishiizumi, B. Lavielle, M. W. Caffee, D. J. Hillegonds, R. C. Finkel, D. Kollar and J. Masari

The concentrations of cosmogenic radionuclides and noble gases in Pitts (IAB) and Horse Creek (ungrouped) provide unambiguous evidence that both irons have a complex exposure history with a first-stage irradiation of 100–600 Myr under high shielding, followed by a second-stage exposure of ˜1 Myr as small objects. The first-stage exposure ages of ˜100 Myr for Horse Creek and ˜600 Myr for Pitts are similar to cosmic-ray exposure ages of other iron meteorites, and most likely represent the Yarkovsky orbital drift times of irons from their parent bodies in the main asteroid belt to one of the nearby chaotic resonance zones. The short second-stage exposure ages indicate that collisional debris from recent impact events on their precursor objects was quickly delivered to Earth. The short delivery times suggests that the recent collision events occurred while the precursor objects of Horse Creek and Pitts were either very close to the chaotic resonance zones or already in Earth-crossing orbits. Since the cosmogenic noble gas records of Horse Creek and Pitts indicate a minimum radius of a few meters for the precursor objects, but do not exclude km-sized objects, we conclude that these irons may represent fragments of two near-Earth asteroids, 3103 Eger and 1986 DA, respectively. Finally, we used the cosmogenic nuclide concentrations in Horse Creek, which contains 2.5 wt% Si, to test current model calculations for the production of cosmogenic 10Be, 26Al, and neonisotopes from iron, nickel, and silicon.


JPEG - 3.7 ko
Geomicrobiology Journal

Microbial Investigations of Opalinus Clay, an Argillaceous Formation as a Potential Host Rock under Evaluation for a Radioactive Waste Repository

Geomicrobiology Journal, 25(5) (2008) 240-249

Poulain S., Sergeant C., Simonoff M., Le Marrec C., Altmann S.

Various deep, compact, sedimentary formations have been studied in recent years as potential host rock for a repository for high-level, long-lived radioactive waste. Considering that microbial activities may influence radionuclide chemistry and migration in such environments, we investigated the potential presence of microorganisms in the Opalinus Clay formation, from unperturbed sediment samples (i.e., not affected by gallery excavation and borehole drilling) recovered under aseptic conditions in the Mont Terri Underground Rock Laboratory (Switzerland). A combination of molecular biology techniques and a cultivation-based approach suggested the presence of a few sparse autochthonous microbial cells in the Opalinus Clay. For the first time, ribosomal RNA (rRNA) genes were sequenced from enrichment cultures from such samples. The results suggested that at least two of the bacterial strains isolated were likely unknown species of the Sphingomonas and Alicyclobacillus genera, as their fully-sequenced 16S-rRNA genes shared less than 97% similarity with validly published sequences. Early genetic divergence occurring after physical isolation of bacterial ancestors in the geosphere by the sedimentation process or following later geological events may have resulted in the generation of particular taxa in the subsurface.


GIF - 4.2 ko
Nuclear Instruments and Methods in Physics Research B

Cross sections for the production of helium, neon, and argon isotopes by proton-induced reactions on iron and nickel

Nucl. Instr. Meth. Phys. Res. B266 (2008)2-12

K. Ammon, I. Leya, B. Lavielle, E. Gilabert, J.-C. David, U. Herpers, and R. Michel

We measured integral thin target cross sections for the proton-induced production of 3He, 4He, 21Ne, 22Ne, 36Ar and 38Ar from Fe and Ni from the respective reaction thresholds up to 1.6 GeV. The production of noble gas isotopes, especially 4He, from Fe and Ni is of special importance for design studies of accelerator driven systems and/or energy amplifier, because Fe is the main structural material in almost every design study. Furthermore, the cross sections are needed to establish the first physical model calculations for the production of cosmogenic nuclides in iron meteorites. As a result of our new measurements there now exist for both target elements a complete and consistent database for the production of noble gas isotopes. The experimental data are compared to results from the theoretical nuclear model codes INCL4/ABLA and TALYS. This comparison clearly demonstrates again that experimental data are still needed because the predictive power of nuclear model codes, though permanently improving, does.


GIF - 2.8 ko
Journal of Nuclear Materials

Study of radiogenic helium diffusion in the β-Thorium Phosphate Diphosphate ceramic

Journal of Nuclear Materials 373 (2008) 112-118

A. Özgümüs, E. Gilabert, N. Dacheux, C. Tamain and B. Lavielle

\beta-Thorium phosphate diphosphate polycrystalline ceramic is considered as a promising candidate for the immobilization of actinides in the field of a long-term storage. In order to study the behavior of the ceramic in relation with the evacuation of helium produced by actinides and daughters disintegrations, the release of radiogenic helium from a sintered pellet aged over an about six year period was studied by thermal desorption and high resolution mass spectrometry. The apparent diffusion coefficients are determined for different annealing sequences and are approximately the same for zircon and britholite at low temperature and uranium dioxide ceramic at high temperature. The apparent diffusion coefficients are found to be (7 ± 3) · 10-22 m2 s-1 and (1.5 ± 0.5) · 10-20 m2 s-1 at 20°C and 120°C, respectively. The activation energy for the apparent diffusion process encompassing both volume and inter-granular diffusion is estimated at 45 ± 15 kJ mol-1 in the studied temperature range (20–1020°C).

Année 2007

JPEG - 4.3 ko
pas de couverture

Comportement physico-chimique de l’uranium et du technétium dans le cycle du combustible nucléaire actuel et futur

Journ. Chim. Russe (J. de la Soc. De Chim. D.I. Mendeleïev), 51(6) (2007) 11-23

Peretrukhin V.F., Moisy Ph., Maslennikov A.G., Sergeant C., Guerman K.E., David F., Fourest B., Simonoff M., Tsivadze A.J., Lecomte M.





JPEG - 8.8 ko
Comptes Rendus de l\’Académie des Sciences

Microorganisms and migration of radionuclides in environment

Comptes Rendus Chimie, Volume 10, Issues 10-11, October-November 2007, Pages 1092-1107

Monique Simonoff, Claire Sergeant, Sébastien Poulain, Michael S. Pravikoff

Amongst all the fission fragments, actinides and activation products coming from the nuclear energy processes, a dozen radionuclides are a hazard for Man and environment, due to their half-life and toxicity. For the last 3.5e4 billion years (Ga), microorganisms have been present on Earth in all sorts of surroundings, even the most hostile ones, characterized by extreme pH, temperature and/or radioactivity. To grow and multiply, they developed enzymatically induced oxido-reduction reactions by coupling reduction of metals/metalloids with oxidation of organic matter, which, in turn, may change soluble forms of radionuclides or stable elements into non-soluble forms. When this happens, microorganisms contribute to fix the radionuclides and prevent dissemination.


JPEG - 8.6 ko
Applied Microbiology and Biotechnology

Characterization of Technetium(VII) reduction by cell suspensions of thermophilic bacteria and archae

Applied Microbiology and Biotechnology 76 (2007) 467-472

Chernyh N.A., Gavrilov S.N., Sorokin V.V., German K.E., Sergeant C., Simonoff M., Robb F., Slobodkin A.I.

Washed cell suspensions of the anaerobic hyperthermophilic archaea Thermococcus pacificus and Thermoproteus uzoniensis and the anaerobic thermophilic gram-positive bacteria Thermoterrabacterium ferrireducens and Tepidibacter thalassicus reduced technetium [99Tc(VII)], supplied as soluble pertechnetate with molecular hydrogen as an electron donor, forming highly insoluble Tc(IV)-containing grayish-black precipitate. Apart from molecular hydrogen, T. ferrireducens reduced Tc(VII) with lactate, glycerol, and yeast extract as electron donors, and T. thalassicus reduced it with peptone. Scanning electron microscopy and X-ray microanalysis of cell suspensions of T. ferrireducens showed the presence of Tc-containing particles attached to the surfaces of non-lysed cells. This is the first report on the reduction in Tc(VII) by thermophilic microorganisms of the domain Bacteria and by archaea of the phylum Euryarchaeota.


JPEG - 3.7 ko
Geomicrobiology Journal

Microbial community analysis of Opalinus Clay drill core samples from the Mont Terri Underground Research laboratory, Switzerland

Geomicrobiology Journal 24 (2007) 1-17

Stroes-Gascoyne S., Schippers A., Schwyn B., Poulain S., Sergeant C., Le Marrec C., Simonoff M., Altmann S., Nagaoka T., Mauclaire L., McKenzie J., Daumas S., Vinsot A., Beaucaire C., Matray J. M.

Opalinus Clay is a candidate host rock for a high-level radioactive waste repository in Switzerland. Microbial metabolism and its by-products could affect the physical and (geo)chemical conditions in such a repository. This study investigated the occurrence of indigenous microbes, their community size and-structure in an Opalinus Clay core from the Mont Terri Underground Research Laboratory, Switzerland, drilled with aseptic techniques. Core sub-samples were distributed to five laboratories, where they were analysed with microscopy, culture-and molecular biology techniques. Evidence supporting a viable microbial community in Opalinus Clay included : five positive culture results (including for sulphate-reducing bacteria, SRB) out of 20 culture attempts ; extraction of 64 ng phospholipid fatty acids (PLFA) per g clay, suggesting the presence of viable cells ; detection of PLFA biomarkers for anaerobic Gram-negative bacteria and SRB ; and the presence of sufficient nutrients to support growth of indigenous and non-indigenous microorganisms for two months. Evidence against a thriving microbial community in Opalinus Clay included : 15 negative culture results out of 20 attempts ; lack of cells by application of microscope techniques (phase contrast, AODC, CARD-FISH) ; consistent failure to extract PCR-amplifiable DNA from the core ; the presence of 14 times higher amounts of lipids indicative of cell debris than those indicative of viable cells (PFLA) ; very small pore sizes ; and very low water content. The combined results of this study (and evidence from other studies in comparable environments) suggest that unperturbed Opalinus Clay appears to contain only a small viable microbial community, which is probably metabolically almost inactive (dormant), due to space and water restrictions. However, any disturbances that would provide space, water and nutrients, as would be the case during repository excavation and construction, could revive the dormant organisms, unless the host rock was kept intact.


GIF - 1.5 ko
Ultrasonics Sonochemistry

Comparative study of sonochemical reactors with different geometry using thermal and chemical probes

Ultrasonics Sonochemistry 14 (2007) 330-336

Nikitenko S. I., Le Naour C., Moisy P.

Laboratory scale 20 kHz sonochemical reactors with different geometries have been tested using thermal probes, the kinetics of H2O2 formation, and the kinetics of diphenylmethane (DPhM) sonochemical darkening. Results revealed that the overall sonochemical reaction rates in H2O and DPhM are driven by the total absorbed acoustic energy and roughly independent the geometry of the studied reactors. However, the sonochemical efficiency, defined as g = VG/S, where G is a sonochemical yield of H2O2, V is a volume of sonicated liquid, and S is a surface of the sonotrode, was proved to increase with the decrease of S. This phenomenon was explained by growing of the maximum cavitating bubble size with ultrasonic intensity and its independence towards the specific absorbed acoustic power. For the cleaning bath reactor the kinetics of the sonochemical reactions in H2O and DPhM depends strongly on the reaction vessel materials : the reaction rates decreased with the increase of the materials elasticity. Kinetic study of H2SO4 sonolysis using a sonoreactor without direct contact


GIF - 3.8 ko
Bulletin de la Société Géologique de France

The contribution of water geochemistry to the understanding of the regional hydrogeological system

Mémoires de la Société géologique de France 178 (2007) 91-114

Buschaert S., Giannesini S., Benedetti L., Lavastre V., Gaucher E. C., Lacroix M., Lavielle B., Michelot J.-L., France-Lanord C., Bourles D., Finkel R., Lancelot J., Dewonck S., Vinsot A.

The main results of hydrogeochemical investigations around the Andra Underground Research Laboratory (URL) located in eastern part of the Paris Basin are described hereafter. Groundwater data (chemistry and isotopic composition) have been acquired all around the URL to determine the origin and residence time of water circulations in limestones of Oxfordian and Dogger age, surrounding the Callovo-Oxfordian argillites, and to determine the hydrogeologic role of the argillites regarding aquifers. The main geochemical result is that deep groundwaters from Oxfordian and Dogger limestones are significantly dissimilar to waters of superficial formations. Chemical and isotopic compositions indicate differences between these two deep-aquifer groundwaters. Groundwaters from the Oxfordian limestone are typically meteoric while some groundwater samples from Dogger limestone may correspond to a mixture of meteoric-brine water. Geochemical and hydrogeologic evidence indicates that these deep samples are old groundwaters. Water from Oxfordian limestone may have residence times of the order of 104-105 year, while the age of water in the Dogger is probably older. Natural tracer studies in the overall sedimentary series indicate that the argillites allow chlorine transfer by diffusion from the Dogger to Oxfordian aquifer. For the porewater of argillites, the approach is totally different : geochemical modelling has been developed to define the chemistry which relies entirely on a complete set of measured physical and chemical parameters.

Année 2006

GIF - 4.2 ko
Nuclear Instruments and Methods in Physics Research B

Three-dimensional densitometry imaging of diatom cells using STIM tomography

Nuclear Instruments and Methods in Physics Research B 249 (2006) 653-659 Seventeenth International Conference on Ion Beam Analysis, Séville (2006)

C. Habchi, D.T. Nguyen, G. Devès, S. Incerti, L. Lemelle, P. Le Van Vang, Ph. Moretto, R. Ortega, H. Seznec, A. Sakellariou, C. Sergeant, A. Simionovici, M.D. Ynsa, E. Gontier, M. Heiss, T. Pouthier, A. Boudou, F. Rebillat

Scanning transmission ion microscopy tomography (STIM-T) was carried out on diatom cells with the aim of displaying their 3D structure and performing density measurements on their silica skeleton. Two software packages were compared for data reduction : TomoRebuild, based on a simple filtered backprojection algorithm, and DISRA, an iterative program. Silicon carbide microfibres of known density were also analysed as reference specimens. Similar results were obtained with both algorithms, demonstrating the ability of STIM-T to provide density measurements at the cell level without requiring any standard calibration samples. This unique feature stresses the interest of STIM-T to accurately normalise X ray emission micro-tomography data from synchrotron radiation (SXRF : synchrotron radiation X-ray fluorescence) or ion beam sources (PIXE : particle induced X-ray emission). Possible enhancements of the DISRA code are discussed in order to facilitate its use for the reconstruction of future PIXE/STIM tomography data. A ‘‘nanoprobe’’ coupled to a Singletron accelerator, allowing a spatial resolution of a few tens of nanometers, is going to be built in the coming months at the Centre d’Etudes Nucléaires de Bordeaux Gradignan (CENBG). This new facility will bring promising applications in imaging and analysis at the sub-cellular level.


JPEG - 6.3 ko
Radiochimica Acta

Technetium sorption by stibnite from natural water

Radiochimica Acta 94 (2006) 665-669

Peretroukhine V. F., Sergeant C., Devès G., Poulain S., Vesvres M.-H., Simonoff M.

The main results of hydrogeochemical investigations around the Andra Underground Research Laboratory (URL) located in eastern part of the Paris Basin are described hereafter. Groundwater data (chemistry and isotopic composition) have been acquired all around the URL to determine the origin and residence time of water circulations in limestones of Oxfordian and Dogger age, surrounding the Callovo-Oxfordian argillites, and to determine the hydrogeologic role of the argillites regarding aquifers. The main geochemical result is that deep groundwaters from Oxfordian and Dogger limestones are significantly dissimilar to waters of superficial formations. Chemical and isotopic compositions indicate differences between these two deep-aquifer groundwaters. Groundwaters from the Oxfordian limestone are typically meteoric while some groundwater samples from Dogger limestone may correspond to a mixture of meteoric-brine water. Geochemical and hydrogeologic evidence indicates that these deep samples are old groundwaters. Water from Oxfordian limestone may have residence times of the order of 104-105 year, while the age of water in the Dogger is probably older. Natural tracer studies in the overall sedimentary series indicate that the argillites allow chlorine transfer by diffusion from the Dogger to Oxfordian aquifer. For the porewater of argillites, the approach is totally different : geochemical modelling has been developed to define the chemistry which relies entirely on a complete set of measured physical and chemical parameters.

Année 2005

GIF - 4.2 ko
Nuclear Instruments and Methods in Physics Research B

Calcium, potassium, iron, copper and zinc concentrations in the white and gray matter of the cerebellum and corpus callosum in brain of four genetic mouse strains

Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms, Volume 231, Issues 1-4, April 2005, Pages 234-238

C. Sergeant, M.H. Vesvres, G. Devès, F. Guillou

In the central nervous system, metallic cations are involved in oligodendrocyte maturation and myelinogenesis. Moreover, the metallic cations have been associated with pathogenesis, particularly multiple sclerosis and malignant gliomas. The brain is vulnerable to either a deficit or an excess of available trace elements. Relationship between trace metals and myelinogenesis is important in understanding a severe human pathology : the multiple sclerosis, which remains without efficient treatment. One approach to understand this disease has used mutant or transgenic mice presenting myelin deficiency or excess. But to date, the concentration of trace metals and mineral elements in white and gray matter areas in wild type brain is unknown. The aim of this study is to establish the reference concentrations of trace metals (iron, copper and zinc) and minerals (potassium and calcium) in the white and gray matter of the mouse cerebellum and corpus callosum. The brains of four different genetic mouse strains (C57Black6/SJL, C57Black6/D2, SJL and C3H) were analyzed. The freeze-dried samples were prepared to allow PIXE (Proton-induced X-ray emission) and RBS (Rutherford backscattering spectrometry) analyses with the nuclear microprobe in Bordeaux. The results obtained give the first reference values. Furthermore, one species out of the fours testes exhibited differences in calcium, iron and zinc concentrations in the white matter.

Année 2004

JPEG - 2.6 ko
Médecine tropicale

Sélénium plasmatique et cardiomyopathie péripartum à Bamako (Mali)

Médecine tropicale : revue du Corps de santé colonial. 64, 2 (2004) 151-154

A. Cénac, K. Touré, M. B. Diarra, C. Sergeant, Y. Jobic, K. Sanogo, M. Dembele, V. Fayol, M. Simonoff

L’insuffisance cardiaque péripartum, fréquente en Afrique soudano-sahélienne, est une cardiomyopathie dilatée de cause inconnue. Parmi les facteurs de risque identifiés une carence alimentaire en sélénium est discutée. Le but de ce travail est de définir le sélénium plasmatique de patientes en insuffisance cardiaque par cardiomyopathie péripartum à Bamako (République du Mali) et de le comparer à celui de sahéliennes en bonne santé à statut obstétrical identique. Afin de préciser le statut en sélénium à Bamako (République du Mali) les auteurs ont dosé le sélénium plasmatique chez 28 Maliennes atteintes de cardiomyopathie dilatée péripartum. Elles ont été appariées à 28 Nigériennes en bonne santé, d’âge comparable et allaitantes, constituant le groupe témoins. Le critère d’appariement a été la parité des malades et des témoins (nombre identique ou proche d’accouchements). Le test de Wilcoxon (test non paramétrique) a été appliqué pour comparer les 2 groupes, une valeur de p < 0,05 étant significative. Le sélénium plasmatique des patientes de Bamako (65 ± 17 ng/ml) est significativement plus bas que celui des Nigériennes en bonne santé de Niamey (78 ± 17 ng/ml, p = 0,01). Conclusion. La sélénémie des malades avec cardiomyopathie dilatée péripartum à Bamako est plus basse que dans la population témoin appariée, en accord avec les faits constatés antérieurement à Niamey.


JPEG - 2.2 ko
Metal Ions

Trace metals in human retina during aging period

Metal Ions in Biology and Medicine (2004) 491-495

Sergeant C., Vesvres M.-H., S Pravikoff M., Devès G., Yefimova M., Jonet L., Valtink M., Courtois Y., Jeanny J.-C.





JPEG - 4.3 ko
pas de couverture

Production rates for cosmogenic krypton and argon isotopes in H Chondrites with known 36Cl – 36Ar ages

Antarctic Meteorite Research 17 (2004) 185-199

I. Leya, E. Gilabert, B. Lavielle, U. Wiechert, R. Wieler

We present physical model calculations for the production of cosmogenic Kr isotopes in stony meteorites and compare the model results with measured data for bulk samples of 12 H-chondrites which recently had been investigated for their 36Cl-36Ar cosmic-ray exposure ages and light noble gas production rates. The correlation between P(81Kr)P(83Kr) and P(78Kr)P(83Kr) modelled here is significantly different from the classical relation commonly used to derive 81Kr-Kr exposure ages. For both relations, the 81Kr ages scatter considerably around the respective 36Cl-36Ar ages, but the new relation on average yields a somewhat better agreement between 81Kr-Kr and 36Cl-^<36>Ar ages. The calculations combined with concentration measurements of the main target elements for the production of cosmogenic Kr (Rb, Sr, Y, Zr, and Nb) show that target element chemistry does hardly influence the isotopic composition of cosmogenic Kr in bulk chondrites. These calculations also confirm earlier conclusions that the isotopic systematics of cosmogenic Kr in lunar samples are applicable for chondrites too. We derived an average 38Ar production rate at average shielding (22Ne21Ne=1.11) of (0.0431±0.0035)×10-8 cm3 STP(g×Myr).

Année 2003

GIF - 4.6 ko
Journal of Environmental Radioactivity

Technetium species induced in maize as measured by phosphorimager

Journal of Environmental Radioactivity, Volume 70, Issues 1-2, 2003, Pages 139-154 M. Simonoff, T. V. Khijniak, C. Sergeant, M. H. Vesvres, M. S. Pravikoff, E. Leclerc-Cessac, G. Echevarria, S. Denys

Leaves of plants have the ability to accumulate the long-lived fission product 99Tc. In the present work, an attempt was made to separate and characterize technetium species formed in maize grown on soil contaminated with TcVIIO4- solution. Data obtained from selective extraction, a Phosphorimager and liquid scintillation were employed.


GIF - 4.2 ko
Nuclear Instruments and Methods in Physics Research B

Iron, transferrin and myelinogenesis

Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms, Volume 210, September 2003, Pages 349-353

C. Sergeant, M. H. Vesvres, G. Devès, B. Baron, F. Guillou

Transferrin (Tf), the iron binding protein of vertebrates serum, is known to be synthesized by oligodendrocytes (Ols) in the central nervous system. It has been postulated that Tf is involved in Ols maturation and myelinogenesis. This link is particularly important in the understanding of a severe human pathology : the multiple sclerosis, which remains without efficient treatment. We generated transgenic mice containing the complete human Tf gene and extensive regulatory sequences from the 50 and 30 untranslated regions that specifically overexpress Tf in Ols. Brain cytoarchitecture of the transgenic mice appears to be normal in all brain regions examined, total myelin content is increased by 30% and motor coordination is significantly improved when compared with non-transgenic littermates. Tf role in the central nervous system may be related to its affinity for metallic cations. Normal and transgenic mice were used for determination of trace metals (iron, copper and zinc) and minerals (potassium and calcium) concentration in cerebellum and corpus callosum. The freeze-dried samples were prepared to allow proton-induced X-ray emission and Rutherford backscattering spectrometry analyses with the nuclear microprobe in Bordeaux. Preliminary results were obtained and carbon distribution was revealed as a very good analysis to distinguish precisely the white matter region. A comparison of metallic and mineral elements contents in brain between normal and transgenic mice shows that iron, copper and zinc levels remained constant. This result provides evidence that effects of Tf overexpression in the brain do not solely relate to iron transport.


JPEG - 7.3 ko
Czechoslovak Journal of Physics

Microbial reduction of 99Tc (TcO4-) in the anaerobic alkaline conditions by Genus Holomonas bacteria

Czechoslovak Journal of Physics, 53, suppl A (2003) 113-117

Khijniak T., Simonoff M., Medvedeva-Lyalikova N., Sergeant C., Simonoff G.





JPEG - 9.1 ko

Reduction of pertechnetate by haloalcaliphilic strains of Halomonas

FEMS Microbiology Ecology, 44 (1), 109-115, 2003

Khijniak T., Simonoff M., Medvedeva-Lyalikova N., Sergeant C.




Année 2002

JPEG - 2.2 ko
Metal Ions

Technetium species induced in maize

Metal Ions in Biology and Medicine, vol VII, John Libbey Eurotext, Paris, 2002, 275-278

Sergeant C., Simonoff M., Khijniak T.





JPEG - 8.5 ko
Meteoritics & Planetary Science

Production of krypton and xenon isotopes in thick stony and iron targets isotropically irradiated with 1600 MeV protons

Meteoritics & Planetary Science 37,951-976 (2002)

E. Gilabert, B. Lavielle, R. Michel, I. Leya, S. Neumann, U. Herpers

Two spherical targets made of gabbro with a radius of 25 cm and of steel with a radius of 10 cm were irradiated isotropically with 600 MeV protons at the SATURNE synchrotron at Laboratoire National Satume (LNS)/CEN Saclay, in order to simulate the production of nuclides in meteorites induced by galactic cosmic-ray protons in space. These experiments supply depth-dependent production rate data for a wide range ofradioactive and stable isotopes in up to 28 target elements. In this paper, we report results for 78Kr, 80-86Kr isotopes in Rb, Sr, Y and Zr and for 124Xe, 126Xe, 128-132Xe, 134Xe, 136Xe isotopes in Ba and La. Krypton and xenon concentrations have been measured at different depths in the spheres by using conventional mass spectrometry. Based on Monte-Carlo techniques, theoretical production rates are calculated by folding depth-dependent spectra of primary and secondary protons and secondary neutrons with the excitation functions of the relevant nuclear reactions. The comparison of the model calculation results with experimental data in the thick target experiments performed at LNS and previously at CERN have allowed adjustments of the poorly known excitation functions ofneutron-induced reactions. Thus, for the two experiments at SATURNE, excellent agreement is obtained between experimental and calculated production rates for most Kr and Xe isotopes in all investigated target elements. Only Xe production in Ba in the gabbro is underestimated by the calculations by -25%. This work validates the approach of the thin-target model calculations ofcosmogenic nuclide production rates in the attempt ofmodeling the interaction of galactic cosmic-ray protons with stony and iron meteorites in space as well as with lunar samples.


Année 2001

GIF - 4.2 ko
Nuclear Instruments and Methods in Physics Research B

Iron and other elements (Cu, Zn, Ca) contents in retina of rats during development and hereditary retinal degeneration

Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms, Volume 181, Issues 1-4, July 2001, Pages 533-538

C. Sergeant, Y. Llabadora, G. Devès, M. H. Vesvres, M. Simonoff, M. Yefimova, Y. Courtois and J. C. Jeanny

The retina as well as other tissues needs iron to survive, but modifications in iron metabolism have also been suggested to contribute to cerebral neurodegenerative diseases. Our study was intended to investigate iron distribution in the retina of normal rats and Royal College of Surgeons (RCS) rats affected by hereditary degeneration of the photoreceptors at different developmental stages (35, 45 and 55 days after birth).

Iron (Fe) distribution was determined by proton induced X-ray emission (PIXE) microanalysis on retinal sections and compared to other tissues (cornea, liver, spleen) and to other elements (Cu, Zn, Ca). Elemental concentrations were determined in different retinal layers especially the photoreceptors, which are progressively altered and disappear in the RCS rats.

Iron is unevenly distributed throughout the rat retina. The highest concentration is observed in the choroid and the retinal pigmented epithelium and in the inner segments of photoreceptors. Iron content is lower in the outer segments but still significant. It increases during both the development and the disease at the level of the segments. This last localised iron increase can result in an overproduction of free radicals and be correlated with the photoreceptor cell loss. The distributions of other elements (Cu, Zn, Ca) revealed interesting temporal progressions.