The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
E Geiger - One of the best experts on this subject based on the ideXlab platform.
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modelling Nuclear fuel behaviour with taf id calculations on the verdon 1 experiment representative of a Nuclear Severe Accident
Journal of Nuclear Materials, 2019Co-Authors: E Geiger, Y Pontillon, C Gueneau, E C CorcoranAbstract:Abstract The chemical behaviour of the main elements present in a PWR irradiated fuel sample (UO2 fuel, Zr from the Zircaloy-cladding, Pu, Np, and fission products such as Ba, Ce, Cs, Gd, I, La, Mo, Nd, Pd, Rh, Ru, Sr, Tc, Te, etc.) submitted to a Nuclear Severe Accident type sequence (VERDON-1 experiment) has been investigated by thermodynamic calculations using the TAF-ID database. Particular emphasis has been placed on the chemical behaviour of the fission products Ba, Cs, Mo, and Zr, and the interactions between the Zircaloy-cladding and the UO2 matrix. Calculation results have been compared to experimental observations completed during the VERDON-1 experiment (instantaneous release of fission products and final chemical state of elements in the sample). Results presented in this manuscript do not account for non-equilibrium phenomena that have a major impact on fission product behaviour (e.g., chemical diffusion, mass transport induced by temperature gradients in the fuel pellet, etc.). None the less, these TAF-ID calculations have described accurately the melting of the sample following the formation of a mixed (U,Zr)O2-x phase because of the interaction between the fuel and the Zircaloy-cladding. Furthermore, calculations have assisted in the explanation of the instantaneous released fractions observed for Ba and Mo during the experiment (as a function of the experiment atmosphere and temperature).
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fission products behaviour in uo2 submitted to Nuclear Severe Accident conditions
Journal of Physics: Conference Series, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, Pier Lorenzo Solari, M SalomeAbstract:The objective of this work was to study the molybdenum chemistry in UO2 based materials, known as SIMFUELS. These materials could be used as an alternative to irradiated Nuclear fuels in the study of fission products behaviour during a Nuclear Severe Accident. UO2 samples doped with 12 stable isotopes of fission products were submitted to annealing tests in conditions representative to intermediate steps of Severe Accidents. Samples were characterized by SEM-EDS and XAS. It was found that Mo chemistry seems to be more complex than what is normally estimated by thermodynamic calculations: XAS spectra indicate the presence of Mo species such as metallic Mo, MoO2, MoO3 and Cs2MoO4.
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insights on fission products behaviour in Nuclear Severe Accident conditions by x ray absorption spectroscopy
Journal of Nuclear Materials, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, G Ducros, Pier Lorenzo SolariAbstract:Many research programs have been carried out aiming to understand the fission products behaviour during a Nuclear Severe Accident. Most of these programs used highly radioactive irradiated Nuclear fuel, which requires complex instrumentation. Moreover, the radioactive character of samples hinders an accurate chemical characterisation. In order to overcome these difficulties, SIMFUEL stand out as an alternative to perform complementary tests. A sample made of UO$_2$ doped with 11 fission products was submitted to an annealing test up to 1973 K in reducing atmosphere. The sample was characterized before and after the annealing test using SEM-EDS and XAS at the MARS beam-line, SOLEIL Synchrotron. It was found that the overall behaviour of several fission products (such as Mo, Ba, Pd and Ru) was similar to that observed experimentally in irradiated fuels and consistent with thermodynamic estimations. The experimental approach presented in this work has allowed obtaining information on chemical phases evolution under Nuclear Severe Accident conditions, that are yet difficult to obtain using irradiated Nuclear fuel samples.
Pier Lorenzo Solari - One of the best experts on this subject based on the ideXlab platform.
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fission products behaviour in uo2 submitted to Nuclear Severe Accident conditions
Journal of Physics: Conference Series, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, Pier Lorenzo Solari, M SalomeAbstract:The objective of this work was to study the molybdenum chemistry in UO2 based materials, known as SIMFUELS. These materials could be used as an alternative to irradiated Nuclear fuels in the study of fission products behaviour during a Nuclear Severe Accident. UO2 samples doped with 12 stable isotopes of fission products were submitted to annealing tests in conditions representative to intermediate steps of Severe Accidents. Samples were characterized by SEM-EDS and XAS. It was found that Mo chemistry seems to be more complex than what is normally estimated by thermodynamic calculations: XAS spectra indicate the presence of Mo species such as metallic Mo, MoO2, MoO3 and Cs2MoO4.
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insights on fission products behaviour in Nuclear Severe Accident conditions by x ray absorption spectroscopy
Journal of Nuclear Materials, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, G Ducros, Pier Lorenzo SolariAbstract:Many research programs have been carried out aiming to understand the fission products behaviour during a Nuclear Severe Accident. Most of these programs used highly radioactive irradiated Nuclear fuel, which requires complex instrumentation. Moreover, the radioactive character of samples hinders an accurate chemical characterisation. In order to overcome these difficulties, SIMFUEL stand out as an alternative to perform complementary tests. A sample made of UO$_2$ doped with 11 fission products was submitted to an annealing test up to 1973 K in reducing atmosphere. The sample was characterized before and after the annealing test using SEM-EDS and XAS at the MARS beam-line, SOLEIL Synchrotron. It was found that the overall behaviour of several fission products (such as Mo, Ba, Pd and Ru) was similar to that observed experimentally in irradiated fuels and consistent with thermodynamic estimations. The experimental approach presented in this work has allowed obtaining information on chemical phases evolution under Nuclear Severe Accident conditions, that are yet difficult to obtain using irradiated Nuclear fuel samples.
Y Pontillon - One of the best experts on this subject based on the ideXlab platform.
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modelling Nuclear fuel behaviour with taf id calculations on the verdon 1 experiment representative of a Nuclear Severe Accident
Journal of Nuclear Materials, 2019Co-Authors: E Geiger, Y Pontillon, C Gueneau, E C CorcoranAbstract:Abstract The chemical behaviour of the main elements present in a PWR irradiated fuel sample (UO2 fuel, Zr from the Zircaloy-cladding, Pu, Np, and fission products such as Ba, Ce, Cs, Gd, I, La, Mo, Nd, Pd, Rh, Ru, Sr, Tc, Te, etc.) submitted to a Nuclear Severe Accident type sequence (VERDON-1 experiment) has been investigated by thermodynamic calculations using the TAF-ID database. Particular emphasis has been placed on the chemical behaviour of the fission products Ba, Cs, Mo, and Zr, and the interactions between the Zircaloy-cladding and the UO2 matrix. Calculation results have been compared to experimental observations completed during the VERDON-1 experiment (instantaneous release of fission products and final chemical state of elements in the sample). Results presented in this manuscript do not account for non-equilibrium phenomena that have a major impact on fission product behaviour (e.g., chemical diffusion, mass transport induced by temperature gradients in the fuel pellet, etc.). None the less, these TAF-ID calculations have described accurately the melting of the sample following the formation of a mixed (U,Zr)O2-x phase because of the interaction between the fuel and the Zircaloy-cladding. Furthermore, calculations have assisted in the explanation of the instantaneous released fractions observed for Ba and Mo during the experiment (as a function of the experiment atmosphere and temperature).
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fission products behaviour in uo2 submitted to Nuclear Severe Accident conditions
Journal of Physics: Conference Series, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, Pier Lorenzo Solari, M SalomeAbstract:The objective of this work was to study the molybdenum chemistry in UO2 based materials, known as SIMFUELS. These materials could be used as an alternative to irradiated Nuclear fuels in the study of fission products behaviour during a Nuclear Severe Accident. UO2 samples doped with 12 stable isotopes of fission products were submitted to annealing tests in conditions representative to intermediate steps of Severe Accidents. Samples were characterized by SEM-EDS and XAS. It was found that Mo chemistry seems to be more complex than what is normally estimated by thermodynamic calculations: XAS spectra indicate the presence of Mo species such as metallic Mo, MoO2, MoO3 and Cs2MoO4.
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insights on fission products behaviour in Nuclear Severe Accident conditions by x ray absorption spectroscopy
Journal of Nuclear Materials, 2016Co-Authors: E Geiger, Ph Martin, Y Pontillon, G Ducros, Pier Lorenzo SolariAbstract:Many research programs have been carried out aiming to understand the fission products behaviour during a Nuclear Severe Accident. Most of these programs used highly radioactive irradiated Nuclear fuel, which requires complex instrumentation. Moreover, the radioactive character of samples hinders an accurate chemical characterisation. In order to overcome these difficulties, SIMFUEL stand out as an alternative to perform complementary tests. A sample made of UO$_2$ doped with 11 fission products was submitted to an annealing test up to 1973 K in reducing atmosphere. The sample was characterized before and after the annealing test using SEM-EDS and XAS at the MARS beam-line, SOLEIL Synchrotron. It was found that the overall behaviour of several fission products (such as Mo, Ba, Pd and Ru) was similar to that observed experimentally in irradiated fuels and consistent with thermodynamic estimations. The experimental approach presented in this work has allowed obtaining information on chemical phases evolution under Nuclear Severe Accident conditions, that are yet difficult to obtain using irradiated Nuclear fuel samples.
Florent Louis - One of the best experts on this subject based on the ideXlab platform.
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Microhydration of caesium metaborate: structural and thermochemical properties of CsBO_2 + n H_2O (n = 1–4) aggregates
Journal of Molecular Modeling, 2019Co-Authors: Dorra Khiri, Laurent Cantrel, Romain Vandeputte, Sonia Taamalli, Florent LouisAbstract:The structures and thermodynamic properties of microhydrates of caesium metaborate (CsBO_2) of Nuclear safety interest are reported in this work. CsBO_2 + n H_2O ( n = 1−4) molecular complexes were identified on the potential energy surface. The structures were optimized using the ωB97XD DFT method and the aug-cc-pVTZ basis set. Single-point energies were calculated at the CCSD(T)-F12a/awCVTZ and the ωB97XD/aug-cc-pVQZ levels of theory. The standard reaction enthalpies and the standard Gibbs free reaction energies were reported for all molecular complexes. The temperature dependence of Δ_r G °(T) was evaluated for all studied structures over the temperature range 300–2000 K. Total hydration reactions were investigated. The results showed that the mono-hydrated form of CsBO_2 exists only at temperatures lower than 720 K under standard conditions. The influence on the thermodynamic properties of the number of water molecules in the clusters was described, with successive dehydration from 720 to 480 K. In Nuclear Severe Accident conditions, gaseous CsBO_2 will remain unhydrated in the reactor coolant system.
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Microhydration of caesium metaborate: structural and thermochemical properties of CsBO2 + n H2O (n = 1-4) aggregates.
Journal of Molecular Modeling, 2019Co-Authors: Dorra Khiri, Laurent Cantrel, Romain Vandeputte, Sonia Taamalli, Florent LouisAbstract:The structures and thermodynamic properties of microhydrates of caesium metaborate (CsBO2) of Nuclear safety interest are reported in this work. CsBO2 + n H2O (n = 1−4) molecular complexes were identified on the potential energy surface. The structures were optimized using the ωB97XD DFT method and the aug-cc-pVTZ basis set. Single-point energies were calculated at the CCSD(T)-F12a/awCVTZ and the ωB97XD/aug-cc-pVQZ levels of theory. The standard reaction enthalpies and the standard Gibbs free reaction energies were reported for all molecular complexes. The temperature dependence of ΔrG°(T) was evaluated for all studied structures over the temperature range 300–2000 K. Total hydration reactions were investigated. The results showed that the mono-hydrated form of CsBO2 exists only at temperatures lower than 720 K under standard conditions. The influence on the thermodynamic properties of the number of water molecules in the clusters was described, with successive dehydration from 720 to 480 K. In Nuclear Severe Accident conditions, gaseous CsBO2 will remain unhydrated in the reactor coolant system.
Annececile Gregoire - One of the best experts on this subject based on the ideXlab platform.
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study of the iodine kinetics in thermal conditions of a rcs in Nuclear Severe Accident
Annals of Nuclear Energy, 2017Co-Authors: Annececile Gregoire, Y Delicat, C Tornabene, Frederic Cousin, L GasnotAbstract:Abstract During the PHEBUS-FP integral Severe Accidents simulation tests, gaseous iodine was detected in earlier stages of the simulated Accident, coming from the experimental circuit modelling a reactor coolant system. One possible explanation is the existence of some kinetic limitations which promote the persistence of gaseous iodine at low temperature. This paper sums up some analytical and modelling works performed to check this assumption. Results show that the chemical speciation of iodine cannot be calculated by assuming chemical equilibrium, kinetics have to be considered, in particular for oxidising atmosphere with an excess of steam. A kinetic model for gaseous iodine is proposed and qualified by comparison with experimental works. Such modelling should be considered to calculate the transport of iodine through the reactor coolant system for a Severe Accident because it can significantly impact iodine source term evaluations.
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studies on the role of molybdenum on iodine transport in the rcs in Nuclear Severe Accident conditions
Annals of Nuclear Energy, 2015Co-Authors: Annececile Gregoire, Frederic Cousin, Jarmo Kalilainen, H Mutelle, Laurent Cantrel, Ari Auvinen, T Haste, S SobanskaAbstract:Abstract The effect of molybdenum on iodine transport in the reactor coolant system (RCS) under PWR Severe Accident conditions was investigated in the framework of the EU SARNET project. Experiments were conducted at the VTT-Institute and at IRSN and simulations of the experimental results were performed with the ASTEC Severe Accident simulation code. As molybdenum affects caesium chemistry by formation of molybdates, it may have a significant impact on iodine transport in the RCS. Experimentally it has been shown that the formation of gaseous iodine is promoted in oxidising conditions, as caesium can be completely consumed to form caesium polymolybdates and is thus not available for reacting with gaseous iodine and leading to CsI aerosols. In reducing conditions, CsI remains the dominant form of iodine, as the amount of oxygen is not sufficient to allow formation of quantitative caesium polymolybdates. An I–Mo–Cs model has been developed and it reproduces well the experimental trends on iodine transport.
