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Rw Grimes - One of the best experts on this subject based on the ideXlab platform.
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Encapsulation of volatile Fission Products in a two-dimensional dicalcium nitride electride
'AIP Publishing', 2020Co-Authors: Kuganathan N, Chroneos A, Rw GrimesAbstract:The efficient capture of volatile Fission Products released during spent fuel reprocessing is a crucial concern for the nuclear community. Here, we apply the density functional theory to examine the efficacy of a two-dimensional dicalcium nitride electride (Ca2N:ē) to encapsulate volatile Fission Products. Encapsulation is endoergic for Kr, Xe, Rb, and Cs meaning that they are not encapsulated. Conversely, strong encapsulation is exhibited for Br, I, and Te with respect to their atoms and dimers as reference states. The preference for Br, I, and Te encapsulation is a consequence of charge transfer from Ca2N:ē to form encapsulated anions. This makes the electride a promising material for the selective trapping of volatile Br, I, and Te
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Trapping of volatile Fission Products by C₆₀
'Elsevier BV', 2018Co-Authors: Kuganathan N, Ak Arya, Rushton Mjd, Rw GrimesAbstract:Carbon based filters provide important safety barriers that remove volatile Fission Products from gas streams. The capacity and efficiency of a filter to trap Fission Products depends upon the strength of the interaction between the Fission Products and the filter material. In this study, we apply density functional theory together with a dispersion correction (DFT + D) to predict structures and energies of volatile Fission product atoms and molecules trapped by buckminsterfullerene (C₆₀). Endohedral encapsulation energies and exohedral association energies show that Rb and Cs are strongly trapped as ions, each transferring approximately one electron to C₆₀ . Kr and Xe are weakly trapped atoms with Xe showing a preference for exohedral association and Kr for endohedral encapsulation. Br, I and Te, while strongly trapped from atoms (and assuming charge from C₆₀) are thermodynamically more stable as neutral covalently bonded Br₂, I₂ and Te₂ molecules weakly trapped through van der Waals forces, exohedrally. Heteronuclear CsBr and CsI were also considered. Both molecules were non-bonded to C₆₀ with similar association energies to those exhibited by Br₂, I₂ and Te₂
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partition of soluble Fission Products between the grey phase zro2 and uranium dioxide
Journal of Nuclear Materials, 2013Co-Authors: M W D Cooper, S C Middleburgh, Rw GrimesAbstract:Abstract The energies to remove Fission Products from UO 2 or UO 2+ x and incorporate them into BaZrO 3 , SrZrO 3 (grey phase constituent phases) and ZrO 2 have been calculated using atomistic scale simulation. These energies provide the thermodynamic drive for partition of soluble Fission Products between UO 2 or UO 2+ x and these secondary oxide constituents of the fuel system. Tetravalent cation partition into BaZrO 3 , SrZrO 3 and ZrO 2 was only preferable for species with smaller radii than Zr 4+ , regardless of uranium dioxide stoichiometry. Under stoichiometric conditions both the larger and the smaller trivalent cations were found to segregate to BaZrO 3 but only the smaller fuel additive elements Cr 3+ and Fe 3+ segregate to SrZrO 3 . Partition from UO 2+ x was always unfavourable for trivalent cations. Additions of excess Cr 3+ (as a fuel additive) are predicted make the partition into BaZrO 3 and SrZrO 3 more favourable from UO 2 for the larger trivalent cations. Trivalent Fission Products with radii smaller than or equal to that of Sm 3+ were identified to segregate into ZrO 2 only from UO 2 . No segregation to SrO or BaO is predicted.
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the stability of Fission Products in uranium dioxide
Philosophical Transactions of the Royal Society A, 1991Co-Authors: Rw Grimes, Charles Richard Arthur CatlowAbstract:A review of experimental data concerning the behaviour of Fission Products in nuclear fuels is used to illustrate the significant variation in solubility exhibited by the different species. To understand the reasons for this variation, it is necessary to obtain a reliable estimate of the solution energies and thus to determine the most stable solution site. This we suggest will be critical in predicting the behaviour of nuclear fuels in both accident and normal operating conditions. We have therefore used the M ott-Littleton simulation technique to calculate solution energies for the Fission Products Br, Kr, Rb, Sr, Y, Zr, Te, I, Xe, Cs, Ba, La and Ce in UO 2. We considered solution at both uranium and oxygen vacancies, the interstitial site and at the di-, tri- and tetra-vacancy complexes. Non-stoichiometry and variable charge state are important components of the model. From these results we conclude that the solubility is significantly affected by non-stoichiometry. In UO 2 and UO 2-x ., Products such as Cs, Rb and Ba are thermodynamically more stable as binary oxide precipitates. Conversely, Y, La and Sr are soluble in UO 2 and UO 2+x , while Cs, Rb, Sr and Ba are only soluble in UO 2+x .The behaviour of I, Br and Te is complicated by the fact that these species are most stable as anions in UO 2 and UO 2-x but as cations in UO 2+x . In our model, Zr and the inert gas species Xe and Kr are always predicted to be insoluble, while CeO 2 will form a solid solution with UO 2.
G Ducros - One of the best experts on this subject based on the ideXlab platform.
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Fission Products and nuclear fuel behavior under severe accident conditions Part 3: Fission Products speciation in the VERDON-1 Sample
Journal of Nuclear Materials, 2017Co-Authors: C. Le Gall, Yves Pontillon, J. Lamontagne, E. Geiger, A. Gallais-during, E. Hanus, G DucrosAbstract:Qualitative and quantitative analyses on the VERDON-1 sample made it possible to obtain valuable information on Fission product behaviour in the fuel during the test. A promising methodology based on the quantitative results of post-test characterisations has been implemented to assess the release fraction of non γ-emitter Fission Products. The order of magnitude of the estimated release fractions for each Fission product was consistent with their class of volatility.
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Fission Products and nuclear fuel behaviour under severe accident conditions part 3 speciation of Fission Products in the verdon 1 sample
Journal of Nuclear Materials, 2017Co-Authors: Le C Gall, Yves Pontillon, J. Lamontagne, E. Geiger, E. Hanus, A Gallaisduring, G DucrosAbstract:Abstract Qualitative and quantitative analyses on the VERDON-1 sample made it possible to obtain valuable information on Fission product behaviour in the fuel during the test. A promising methodology based on the quantitative results of post-test characterisations has been implemented to assess the release fraction of non γ-emitter Fission Products. The order of magnitude of the estimated release fractions for each Fission product was consistent with their class of volatility.
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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: Ernesto Geiger, Ph Martin, G Ducros, Yves Pontillon, 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.
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Use of model materials for Fission Products release study in Severe Accident Conditions
2015Co-Authors: Ernesto Geiger, Ph Martin, Yves Pontillon, R. Bes, G DucrosAbstract:Many integral and analytical research programs, such as PHEBUS FP, HI/VI, VEGA, VERCORS, etc., have been carried out aiming to understand the behaviour of Fission Products during a Nuclear Severe Accident. Most of them used standard PWR or BWR nuclear fuels with burn-ups going from traces up to about 70-80 GWd/t, which implied sophisticated experiments. Another way to study these matters is to use Model Materials doped with stable Fission Products in concentrations representative of a given burn-up, known as SIMFUEL. In order to demonstrate that they are an efficient alternative to irradiated fuel in the SA study, SIMFUEL samples doped with up to 12 Fission Products were submitted to annealing treatments in conditions representative of severe accidents. Samples were characterised before and after the tests by SEM-EDX and XAS, at SOLEIL and ESRF Synchrotrons, which are yet unavailable for irradiated fuels. Despite the limitations of SIMFUELS, it was found that the overall behaviour of Fission Products was similar to that observed for irradiated fuels and also consistent with thermodynamic estimations the common chemical phases other than the fuel matrix were reproduced as well as the general Fission Products behaviour, in terms of release from the sample.
Yves Pontillon - One of the best experts on this subject based on the ideXlab platform.
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Fission Products and nuclear fuel behavior under severe accident conditions Part 3: Fission Products speciation in the VERDON-1 Sample
Journal of Nuclear Materials, 2017Co-Authors: C. Le Gall, Yves Pontillon, J. Lamontagne, E. Geiger, A. Gallais-during, E. Hanus, G DucrosAbstract:Qualitative and quantitative analyses on the VERDON-1 sample made it possible to obtain valuable information on Fission product behaviour in the fuel during the test. A promising methodology based on the quantitative results of post-test characterisations has been implemented to assess the release fraction of non γ-emitter Fission Products. The order of magnitude of the estimated release fractions for each Fission product was consistent with their class of volatility.
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Fission Products and nuclear fuel behaviour under severe accident conditions part 3 speciation of Fission Products in the verdon 1 sample
Journal of Nuclear Materials, 2017Co-Authors: Le C Gall, Yves Pontillon, J. Lamontagne, E. Geiger, E. Hanus, A Gallaisduring, G DucrosAbstract:Abstract Qualitative and quantitative analyses on the VERDON-1 sample made it possible to obtain valuable information on Fission product behaviour in the fuel during the test. A promising methodology based on the quantitative results of post-test characterisations has been implemented to assess the release fraction of non γ-emitter Fission Products. The order of magnitude of the estimated release fractions for each Fission product was consistent with their class of volatility.
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An innovative Method to study Volatile Fission Products speciation in nuclear fuels under Severe Accident Conditions
2017Co-Authors: H. Hein, Yves Pontillon, J. Léchelle, Jl. Hazemann, O. Proux, C. Riglet-martial, F. Audubert, C. Le Gall, M. Cologna, M. HolzhauserAbstract:The development of realistic models for Fission Products behavior during a severe accident requires experimental data on Fission Products speciation into the fuel (as irradiated and during the transient) together with thermodynamic predictions. Due to the limitations in terms of experiments and characterization techniques available to study Fission Products speciation in nuclear irradiated fuels, simulant materials (SIMFUEL manufactured thanks to conventional process) are often used. However, these materials do not allow the study of volatile Fission Products because they are totally released during the sintering stage. In the case of SIMFUEL with implanted Fission Products surrogates, the chemical state and the corresponding evolution of the phases during the thermal sequence are not entirely representative of the real case. An innovative method to study volatile Fission Products speciation in SIMFUEL samples has thus been developed. Spark plasma sintering was used to synthesize dense SIMFUEL samples containing cesium in collaboration with the JRC-Karlsruhe within the frame of the GENTLE program. Thermodynamic calculations made using the TAF-ID v.6 associated with the FACTSage software enabled to determine the conditions in which to perform thermal treatments. In-temperature XAS experiments in conditions representative of a sevre accident are developed in collaboration with FAME-UHD beamline at the ESRF (Grenoble, France). Additional thermal treatments will also be performed to enable further characterizations (ceramography, SEM-EDX...).
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Fission Products behaviour in uo2 submitted to nuclear severe accident conditions
Journal of Physics: Conference Series, 2016Co-Authors: Ernesto Geiger, Ph Martin, Yves Pontillon, Pier Lorenzo Solari, Marc SaloméAbstract: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: Ernesto Geiger, Ph Martin, G Ducros, Yves Pontillon, 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.
Charles Richard Arthur Catlow - One of the best experts on this subject based on the ideXlab platform.
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the stability of Fission Products in uranium dioxide
Philosophical Transactions of the Royal Society A, 1991Co-Authors: Rw Grimes, Charles Richard Arthur CatlowAbstract:A review of experimental data concerning the behaviour of Fission Products in nuclear fuels is used to illustrate the significant variation in solubility exhibited by the different species. To understand the reasons for this variation, it is necessary to obtain a reliable estimate of the solution energies and thus to determine the most stable solution site. This we suggest will be critical in predicting the behaviour of nuclear fuels in both accident and normal operating conditions. We have therefore used the M ott-Littleton simulation technique to calculate solution energies for the Fission Products Br, Kr, Rb, Sr, Y, Zr, Te, I, Xe, Cs, Ba, La and Ce in UO 2. We considered solution at both uranium and oxygen vacancies, the interstitial site and at the di-, tri- and tetra-vacancy complexes. Non-stoichiometry and variable charge state are important components of the model. From these results we conclude that the solubility is significantly affected by non-stoichiometry. In UO 2 and UO 2-x ., Products such as Cs, Rb and Ba are thermodynamically more stable as binary oxide precipitates. Conversely, Y, La and Sr are soluble in UO 2 and UO 2+x , while Cs, Rb, Sr and Ba are only soluble in UO 2+x .The behaviour of I, Br and Te is complicated by the fact that these species are most stable as anions in UO 2 and UO 2-x but as cations in UO 2+x . In our model, Zr and the inert gas species Xe and Kr are always predicted to be insoluble, while CeO 2 will form a solid solution with UO 2.
Yoshiaki Oka - One of the best experts on this subject based on the ideXlab platform.
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Measurement of decay heat of fast neutron Fission Products
Progress in Nuclear Energy, 1998Co-Authors: Masatsugu Akiyama, Yoshiaki OkaAbstract:Experimental study on decay heat of fast neutron Fission Products using the fast neutron source reactor YAYOI at the University of Tokyo is reviewed in this paper. The decay heat was measured on 233U, 235U, 239Pu, 238U and 232Th using beta- and gamma-spectroscopic method. Their results were compared with other data and results of summation calculations using some Fission product decay data files, and also have been used in the benchmark experiments for the improvement of Fission product decay data files.