Artículos de revistas: "UO2 Cr doped"

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Cachoir, Christelle, Thierry Mennecart y Karel Lemmens. "Evolution of the uranium concentration in dissolution experiments with Cr-(Pu) doped UO2 in reducing conditions at SCK CEN". MRS Advances 6, n.º 4-5 (18 de marzo de 2021): 84–89. http://dx.doi.org/10.1557/s43580-021-00027-y.

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AbstractCr-doped UO2-based model materials were prepared at SCK CEN, mimicking modern LWR fuels, to understand the influence of Cr doping on the spent fuel dissolution behaviour in geological repository conditions. Tests were carried out with four model materials: depleted UO2, Cr-doped depleted UO2, Pu-doped UO2 and Pu-Cr-doped UO2. Static dissolution experiments have been performed up to 4 months in autoclaves under 10 bar H2 pressure with a Pt/Pd catalyst in media at pH 13.5 and at pH 9. The Cr-doping appeared to reduce the U concentrations by a factor 6 at pH 13.5, but it had no or not much effect at pH 9. Graphic abstract

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2

Cordara, Theo, Hannah Smith, Ritesh Mohun, Laura J. Gardner, Martin C. Stennett, Neil C. Hyatt y Claire L. Corkhill. "Hot Isostatic Pressing (HIP): A novel method to prepare Cr-doped UO2 nuclear fuel". MRS Advances 5, n.º 1-2 (2020): 45–53. http://dx.doi.org/10.1557/adv.2020.62.

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ABSTRACTThe addition of Cr2O3 to modern UO2 fuel modifies the microstructure so that, through the generation of larger grains during fission, a higher proportion of fission gases can be accommodated. This reduces the pellet-cladding mechanical interaction of the fuel rods, allowing the fuels to be “burned” for longer than traditional UO2 fuel, thus maximising the energy obtained. We here describe the preparation of UO2 and Cr-doped UO2 using Hot Isostatic Pressing (HIP), as a potential method for fuel fabrication, and for development of analogue materials for spent nuclear fuel research. Characterization of the synthesised materials confirmed that high density UO2 was successfully formed, and that Cr was present as particles at grain boundaries and also within the UO2 matrix, possibly in a reduced form due to the processing conditions. In contrast to studies of Cr-doped UO2 synthesised by other methods, no significant changes to the grain size were observed in the presence of Cr.

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Kegler, Philip, Martina Klinkenberg, Andrey Bukaemskiy, Gabriel L. Murphy, Guido Deissmann, Felix Brandt y Dirk Bosbach. "Chromium Doped UO2-Based Ceramics: Synthesis and Characterization of Model Materials for Modern Nuclear Fuels". Materials 14, n.º 20 (17 de octubre de 2021): 6160. http://dx.doi.org/10.3390/ma14206160.

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Cr-doped UO2 as a modern nuclear fuel type has been demonstrated to increase the in-reactor fuel performance compared to conventional nuclear fuels. Little is known about the long-term stability of spent Cr-doped UO2 nuclear fuels in a deep geological disposal facility. The investigation of suitable model materials in a step wise bottom-up approach can provide insights into the corrosion behavior of spent Cr-doped nuclear fuels. Here, we present new wet chemical approaches providing the basis for such model systems, namely co-precipitation and wet coating. Both were successfully tested and optimized, based on detailed analyses of all synthesis steps and parameters: Cr-doping method, thermal treatment, reduction of U3O8 to UO2, green body production, and pellet sintering. Both methods enable the production of suitable model systems with a similar microstructure and density as a reference sample from AREVA. In comparison with results from the classical powder route, similar trends upon grain size and lattice parameter were determined. The results of this investigation highlight the significance of subtly different synthesis routes on the properties of Cr-doped UO2 ceramics. They enable a reproducible tailor-made well-defined microstructure, a homogeneous doping, for example, with lanthanides or alpha sources, the introduction of metallic particles, and a dust-free preparation.

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4

Kegler, Philip, Martina Klinkenberg, Felix Brandt, Guido Deissmann y Dirk Bosbach. "Evaluation of the corrosion behavior of modern spent nuclear fuels under repository conditions". Safety of Nuclear Waste Disposal 1 (10 de noviembre de 2021): 91–93. http://dx.doi.org/10.5194/sand-1-91-2021.

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Abstract. In Germany it is planned to directly dispose spent nuclear fuel (SNF) from nuclear power plants together with other high-level radioactive wastes (HLW) from former SNF reprocessing (e.g., vitrified waste), in a deep geological repository for heat-generating wastes – the siting process for this repository was started in 2017 and is ongoing. Based on several decades of research, development, and demonstration (RD&D) it is generally accepted at the technical and scientific level that direct disposal of HLW and SNF in deep mined geological repositories is the safest and most sustainable option (CEC, 2011; IAEA, 2004). The current efforts to improve the performance and accident tolerance of fuels in nuclear power generation resulted in an increased utilization of a variety of new types of light-water reactor (LWR) fuels such as fuels doped with Cr, Al, and Si. This doping leads to a significant change of the microstructure of the fuel matrix. The corrosion behavior of these types of fuels under conditions relevant to deep geological disposal has hardly been studied so far; however, this is of crucial importance as the development of a robust safety case for deep geological disposal of SNF requires a solid understanding of its dissolution behavior over very long time scales (up to 1 million years). To fill this knowledge gap, additional systematic studies on modern doped UO2 fuels were needed. Corrosion experiments with SNF cannot entirely unravel all of the various concurring effects of the dissolution mechanism due to the chemical and structural complexity of SNF and its high beta and gamma radiation field during the first 1000 years; moreover, technical restrictions only allow a very limited number of experiments. Therefore, within the EU-DisCo project (https://www.disco-h2020.eu, last access: 11 October 2021), a very ambitious programme of corrosion studies on irradiated Cr and Al/Cr doped fuels was carried out, which was complemented by systematic single-effect dissolution studies (e.g., with respect to doping level, grain size and thermodynamic aspects) performed on carefully prepared and characterized, simplified UO2-based model materials. Here, we present recent results on the dissolution behavior of tailor-made UO2 model materials in accelerated static batch experiments using H2O2 as simulant for radiolytic oxidants, present in long-term disposal scenarios for SNF in failed container conditions due to the alpha irradiation of water. In these dissolution experiments pure UO2 reference pellets exhibiting different densities and grain sizes, as well as Cr-doped UO2 pellets with various Cr-doping levels, produced using different doping methods having different grain sizes, were used. In addition, Nd-doped and industrially produced Cr- and Cr/Nd-doped UO2 pellets were used to determine the influence of these parameters on the dissolution rates. The dissolution experiments were performed under strictly controlled conditions with respect to exclusion of oxygen, temperature control, and exclusion of light. This bottom-up approach was followed to understand how the addition of Cr-oxide into the fuel matrix affects SNF dissolution behavior under repository relevant conditions. The results of the dissolution experiments performed with real SNF and the model materials obtained by the DisCo partners build the basis for numerical simulations on the dissolution behavior of modern SNF. First results of the data evaluation indicate that the addition of dopants and the consequential modification of the fuel matrix does not lead to a significant change of the dissolution behavior of these fuels under repository relevant conditions compared to standard SNF (i.e. dissolution rates agree within an order of magnitude).

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5

Zacharie-Aubrun, Isabelle, Rebecca Dowek, Jean Noirot, Thierry Blay, Martiane Cabié y Myriam Dumont. "Restructuring in high burn-up UO₂ fuels: Experimental characterization by electron backscattered diffraction". Journal of Applied Physics 132, n.º 19 (21 de noviembre de 2022): 195903. http://dx.doi.org/10.1063/5.0104865.

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This paper discusses the use of electron backscattered diffraction to characterize restructuring in a set of UO2 samples, irradiated in a pressurized water reactor at a burn-up between 35 and 73 GWd/tU, including standard UO2 samples and Cr-doped UO2 samples, to provide a better understanding of restructuring occurring both on the periphery and in the center of high-burn-up pellets. The formation of a high burn-up structure on the periphery of high burn-up UO2 was confirmed in our experiment. We found restructuring associated with bubble formation of all the samples in the central area, with higher irradiation temperatures when the burn-up exceeded 61 GWd/tU, regardless of their initial microstructure. This restructuring tended to progress with the increasing burn-up and to sub-divide the initial grains into sub-grains, with orientations close to that of the parent grains. Radial changes and differences between these samples showed that the burn-up and the temperature were not the only relevant parameters involved in restructuring.

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6

Cooper, M. W. D., D. J. Gregg, Y. Zhang, G. J. Thorogood, G. R. Lumpkin, R. W. Grimes y S. C. Middleburgh. "Formation of (Cr,Al)UO4 from doped UO2 and its influence on partition of soluble fission products". Journal of Nuclear Materials 443, n.º 1-3 (noviembre de 2013): 236–41. http://dx.doi.org/10.1016/j.jnucmat.2013.07.038.

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7

Gonzalez, Jheffry y Martin Ševecek. "Modelling of fission gas release in UO2 doped fuel using transuranus code". Acta Polytechnica CTU Proceedings 37 (6 de diciembre de 2022): 24–30. http://dx.doi.org/10.14311/app.2022.37.0024.

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The expected benefits from Cr-doped fuel are improved retention of fission gases within the pellets due to its large grain size. To demonstrate this, several experiments have been carried out by Halden reactor and Studsvik. These experiments are now being used to benchmark several fuel performance codes among them transuranus code. All this as part of a Coordinate Research Project (CRP) by IAEA named Testing and Simulation for Advanced Technology and Accident Tolerant Fuels (ATF-TS). This work is introducing a novel fission gas diffusivity model for doped fuel in transuranus code. It is observed the benefits of introducing this new model when comparing to the standard model already existing in transuranus. Nevertheless, more work needs to be carried out to fully understand all the phenomena involved in adding dopant in UO2 due to change of thermo mechanical properties.

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8

Terricabras, Adrien J., Sean M. Drewry, Keri Campbell, Elizabeth J. Judge, Darrin D. Byler, Emily S. Teti, Arjen van Veelen, Scarlett Widgeon Paisner y Joshua T. White. "Performance and properties evolution of near-term accident tolerant fuel: Cr-doped UO2". Journal of Nuclear Materials 594 (junio de 2024): 155022. http://dx.doi.org/10.1016/j.jnucmat.2024.155022.

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9

Curti, Enzo y Dmitrii A. Kulik. "Oxygen potential calculations for conventional and Cr-doped UO2 fuels based on solid solution thermodynamics". Journal of Nuclear Materials 534 (junio de 2020): 152140. http://dx.doi.org/10.1016/j.jnucmat.2020.152140.

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10

Introïni, Clément, Jérôme Sercombe, Christine Guéneau y Bo Sundman. "Modeling oxygen transport in Cr doped UO2 fuel with the TAF-ID during power transients". Journal of Nuclear Materials 603 (enero de 2025): 155352. http://dx.doi.org/10.1016/j.jnucmat.2024.155352.

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11

de Lara, A., P. Van Uffelen, G. Nicodemo, G. Zullo, D. Pizzocri y E. Shwageraus. "Consideration of Cr-doped UO2 fuel performance for a Fluoride-Cooled High Temperature Reactor concept". Annals of Nuclear Energy 209 (diciembre de 2024): 110820. http://dx.doi.org/10.1016/j.anucene.2024.110820.

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12

Gorton, Jacob P., Annabelle G. Le Coq, Zane G. Wallen, Christian M. Petrie, Joshua T. White, John T. Dunwoody, Shane Mann, Nathan A. Capps y Andrew T. Nelson. "Modeling and design of a separate effects irradiation test targeting fission gas release from Cr-doped UO2". Nuclear Engineering and Design 429 (diciembre de 2024): 113571. http://dx.doi.org/10.1016/j.nucengdes.2024.113571.

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13

Noirot, Jean, Rébecca Dowek, Isabelle Zacharie-Aubrun, Thierry Blay, Martiane Cabié y Myriam Dumont. "Restructuring in high burn-up pressurized water reactor UO₂ fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy". Journal of Applied Physics 132, n.º 19 (21 de noviembre de 2022): 195902. http://dx.doi.org/10.1063/5.0105072.

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Focussed ion beam - scanning electron microscope (FIB-SEM) 3D examination was conducted on three standard UO2 and one Cr doped UO2 high burn-up pressurized water reactor (PWR) fuel samples. This work complemented other microanalysis examination, including an electron backscattered diffraction (EBSD) work on the polished surface. A parallel article giving the EBSD results was submitted simultaneously. Together, they found, in all the central area of these high burn-up samples: (i) a restructuring of the initial grains into smaller sub-grains forming low angle boundaries and with crystal orientations around that of their parent grains; and (ii) intragranular bubbles mostly situated on these low angle boundaries. The FIB-SEM 3D examination showed how such inter-sub-grain bubbles start as small compact but also small lenticular bubbles, similar to typical small intergranular lenticular bubbles. With increasing burn-up, these lenticular bubbles get thicker and locally interlink to form more complex bubbles. However, no long distance networks, between the sub-grains or between the original grains, were found. Such networks could have been a path for part of the fission gases to reach the grain boundaries, the grain edges (the intersection line of three grain boundaries), and the rod free volumes. These FIB-SEM 3D examinations brought details on the intragranular and intergranular bubbles situation for each studied volume. The distribution of the intragranular bubbles according to their sizes and shapes was exposed. The central restructuring, studied in this work, is likely to play a role in the increase of the fission gas release fractions at high burn-up. This work is an incentive to study further this restructuring and the bubbles formed, combining different approaches.

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14

Smith, Hannah, Théo Cordara, Clémence Gausse, Sarah E. Pepper y Claire L. Corkhill. "Oxidative dissolution of Cr-doped UO2 nuclear fuel". npj Materials Degradation 7, n.º 1 (7 de abril de 2023). http://dx.doi.org/10.1038/s41529-023-00347-4.

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AbstractAlternative UO2 nuclear fuels, incorporating Cr as a dopant, are currently in use in light–water reactors. Dissolution experiments using Cr-doped UO2, performed as a function of Cr content in a simplified groundwater solution and under oxic conditions, established that the addition of Cr to the UO2 matrix systematically reduced the normalised dissolution rate of U at 25 and 40 °C. This effect was most notable under dilute solution conditions, and is the result of galvanic coupling between Cr and U, resulting from the presence of Cr2+ in the UO2 matrix, as corroborated by activation energy determination. Under conditions of solution saturation, where schoepite ((UO2)8O2(OH)12·(H2O)12) and Na2U2O7·6H2O were identified as secondary phases, the rate of U dissolution was invariant with Cr content. Moreover, at 60 °C, the trend was reversed and the rate of U dissolution increased with increasing Cr content. Under these conditions, other factors, including U solubility or bicarbonate-surface interactions, exert a stronger influence on the U dissolution kinetics than Cr. Increased grain size, a feature of Cr-doped UO2 fuel, was also found to reduce the normalised dissolution rate of U. In establishing the mechanisms by which Cr dopants influence UO2 fuel dissolution, it can be concluded that, overall, Cr-doped UO2 nuclear fuel possesses similar dissolution kinetics to undoped UO2 fuel, giving confidence for its eventual disposal in a geological facility.

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15

Murphy, Gabriel L., Robert Gericke, Sara Gilson, Elena F. Bazarkina, André Rossberg, Peter Kaden, Robert Thümmler et al. "Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies". Nature Communications 14, n.º 1 (28 de abril de 2023). http://dx.doi.org/10.1038/s41467-023-38109-0.

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AbstractCr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

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16

Kegler, Philip, Stefan Neumeier, Martina Klinkenberg, Andrey Bukaemskiy, Guido Deissmann, Felix Brandt y Dirk Bosbach. "Accelerated dissolution of doped UO2-based model systems as analogues for modern spent nuclear fuel under repository conditions". MRS Advances, 21 de marzo de 2023. http://dx.doi.org/10.1557/s43580-023-00544-y.

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AbstractSystematic single-effect dissolution studies were carried out on the dissolution behaviour of pure and Cr- or Nd-doped UO2 reference pellets as model materials for spent nuclear fuel with varying doping levels, densities, and grain sizes as well as of industrially produced Cr- and Cr/Nd-doped UO2 pellets. The results were obtained from accelerated static batch dissolution experiments performed under strictly controlled conditions using H2O2 as simulant for radiolytic oxidants formed due to the alpha-irradiation of water. The results indicate that the addition of Cr and the consequential modification of the fuel matrix does not lead to a significant change of the dissolution behaviour of these model materials compared to pure UO2 reference materials. Contrarily, the dissolution rates of Nd-doped pellets are significantly lower than those of pure and Cr-doped pellets. These results provide additional insights into the influence of doping on the dissolution behaviour of modern spent light water reactor fuels under the post-closure conditions expected in a deep geological repository. Graphical abstract

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17

Milena-Pérez, A., L. J. Bonales, N. Rodríguez-Villagra, J. Cobos y H. Galán. "Raman spectroscopy study of the influence of additives (Cr-, Cr/Al-, and Gd) on UO2 dissolution behavior". MRS Advances, 4 de febrero de 2025. https://doi.org/10.1557/s43580-025-01172-4.

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Abstract In this work, Raman spectroscopy (RS) has been used to study the behavior of spent nuclear fuel (SNF) under disposal conditions. In particular, evolutionary Accident-Tolerant Fuels (ATFs) consisting in UO2 doped with Cr and Cr/Al; as well as neutron absorbers (UO2 doped with Gd), has been manufactured and studied. The prepared pellets have been exposed to three different pH leachants (inert media, carbonated media, and young cement water with calcium) for distinct times. RS analyses have been conducted in both the leached and the unleached pellets. The results show that the addition of Cr, and Cr/Al does not lead to a noteworthy change of the pellet surface under the three media considered. Gd doping induces a higher intensity of the so-called “defects band,” which is not dramatically affected after leaching. No secondary phases have been observed. These results are in good agreement with previous studies by XRD and SEM, thus validating RS as an accurate analytical technique. Graphical abstract

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18

Owen, Megan W., Michael W. D. Cooper, Michael J. D. Rushton, Antoine Claisse, William E. Lee y Simon C. Middleburgh. "Diffusion in undoped and Cr-doped amorphous UO2". Journal of Nuclear Materials, enero de 2023, 154270. http://dx.doi.org/10.1016/j.jnucmat.2023.154270.

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19

Rodríguez-Villagra, N., O. Riba, A. Milena-Pérez, J. Cobos, L. Jimenez-Bonales, S. Fernández-Carretero, E. Coene, O. Silva y L. Duro. "Dopant effect on the spent fuel matrix dissolution of new advanced fuels: Cr-doped UO2 and Cr/Al-doped UO2". Journal of Nuclear Materials, junio de 2022, 153880. http://dx.doi.org/10.1016/j.jnucmat.2022.153880.

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20

Smith, Hannah, Luke T. Townsend, Ritesh Mohun, Théo Cordara, Martin C. Stennett, J. Frederick W. Mosselmans, Kristina Kvashnina y Claire L. Corkhill. "Cr2+ solid solution in UO2 evidenced by advanced spectroscopy". Communications Chemistry 5, n.º 1 (1 de diciembre de 2022). http://dx.doi.org/10.1038/s42004-022-00784-3.

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AbstractAdvanced Cr-doped UO2 fuels are essential for driving safe and efficient generation of nuclear energy. Although widely deployed, little is known about their fundamental chemistry, which is a critical gap for development of new fuel materials and radioactive waste management strategies. Utilising an original approach, we directly evidence the chemistry of Cr(3+)2O3–doped U(4+)O2. Advanced high-flux, high-spectral purity X-ray absorption spectroscopy (XAS), corroborated by diffraction, Raman spectroscopy and high energy resolved fluorescence detection-XAS, is used to establish that Cr2+ directly substitutes for U4+, accompanied by U5+ and oxygen vacancy charge compensation. Extension of the analysis to heat-treated simulant nuclear fuel reveals a mixed Cr2+/3+ oxidation state, with Cr in more than one physical form, explaining the substantial discrepancies that exist in the literature. Successful demonstration of this analytical advance, and the scientific underpinning it provides, opens opportunities for an expansion in the range of dopants utilised in advanced UO2 fuels.

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21

Milena-Pérez, A., L. J. Bonales, N. Rodríguez-Villagra, M. B. Gómez-Mancebo y H. Galán. "Oxidation of Accident Tolerant Fuels models based on Cr-doped UO2 for the safety of nuclear storage facilities". Journal of Nuclear Materials, mayo de 2023, 154502. http://dx.doi.org/10.1016/j.jnucmat.2023.154502.

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Artículos de revistas sobre el tema "UO2 Cr doped"

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