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Thermal Decomposition of Lead White for Radiocarbon Dating of Paintings
- Lucile Beck, Cyrielle Messager, Stéphanie Coelho, Ingrid Caffy, Emmanuelle Delqué-Količ, Marion Perron, Solène Mussard, Jean-Pascal Dumoulin, Christophe Moreau, Victor Gonzalez, Eddy Foy, Frédéric Miserque, Céline Bonnot-Diconne
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- Journal:
- Radiocarbon / Volume 61 / Issue 5 / October 2019
- Published online by Cambridge University Press:
- 02 July 2019, pp. 1345-1356
- Print publication:
- October 2019
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Lead carbonates were used as cosmetic and pigment since Antiquity. The pigment, known as lead white, was generally composed of cerussite and hydrocerussite. Unlike most ancient pigments, lead white was obtained by a synthetic route involving metallic lead, vinegar and organic matter. Fermentation of organic matter produces heat and CO2 emission, leading to the formation of carbonates. As lead white is formed by trapping CO2, radiocarbon (14C) dating can thus be considered. We have developed a protocol to prepare lead white. We selected modern pigments for the experiment implementation and ancient cosmetic and paintings for dating. After characterization of the samples by XRD, thermal decomposition of cerussite at various temperatures was explored in order to select the appropriate conditions for painting samples. CO2 extraction yield, SEM and XPS were used to characterize the process. Thermal decomposition at 400°C was successfully applied to mixtures of lead white with other paint components (oil as binder, calcite as filler/extender) and to historical samples. We obtained radiocarbon measurements in agreement with the expected dates, demonstrating that thermal decomposition at 400°C is efficient for a selective decomposition of lead white and that paintings can be directly 14C-dated by dating lead white pigment.
Release of Radiotoxic Elements from High Burn-Up UO2 and MOX Fuel in a Repository
- Jean-Paul Glatz, Paul Carbol, Joaquin Cobos-Sabaté, Thomas Gouder, Frédéric Miserque, Javier Gimenez, Detlef Wegen
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- Journal:
- MRS Online Proceedings Library Archive / Volume 663 / 2000
- Published online by Cambridge University Press:
- 21 March 2011, 449
- Print publication:
- 2000
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In a spent fuel repository the processes that govern the release of radionuclides are dissolution and transport in a possible groundwater flow. The cladding will be the last barrier before the water comes into contact with the fuel, namely with the outer rim of the pellet. Here the heterogeneity of the material due to the irradiation process is responsible for a complex release process. Fission products and minor actinides inventories are considerably higher at the pellet periphery as a result of increased epithermal neutron capture and of migration in the case of the volatile fission products.
The present paper gives a review of experimental activities at the Institute for Transuranium Elements (ITU). Both single effects studies and integral tests are carried out to study the behavior of spent fuel under storage conditions.
Leaching of irradiated UO2 (up to 50 GWd/tU) and MOX (up to 25 GWd/tU) fuel rods with preset cladding defects at 100°C under anoxic or reducing conditions should simulate the realistic case of groundwater coming into contact with a spent nuclear fuel repository. For all main radionuclides the release process can be described considering a two-step dissolution mechanism that includes the initial dissolution of an oxidized layer present on the fuel surface followed by a long-term oxidative matrix dissolution. By means of α-doped (238Pu) UO2 it could be demonstrated, that radiolysis has a significant influence on this dissolution. Especially high initial release rates were found for the volatile cesium and iodine for the reasons mentioned above.
Besides the conventional leaching experiments electrochemical techniques are used to investigate for instance the complex corrosion behavior of the heterogeneous MOX fuel materials or the influence of α-radiolysis on spent fuel dissolution.
In the integral tests mentioned above with large S/V values, reprecipitation of U is likely to happen. Therefore special dynamic test are conducted where this reprecipitation is prohibited and true U solubility can be determined.
Thin layer of UO2 and (U,Pu)O2 doped with various fission products and minor actinides are prepared to study the influence of these elements on the matrix dissolution. When Cs is for instance co-deposited, the U oxidation state changes from U4+ to U6+ for the same O2 pressure possibly indicating a stable Cs uranate. This could be an indirect proof of the existence of such a species in irradiated fuel (e.g. at the grain boundaries).