A5072188931- Nuclear Materials and Properties
- Radioactive element chemistry and processing
- Nuclear reactor physics and engineering
- Radioactive contamination and transfer
- Nuclear materials and radiation effects
- Astro and Planetary Science
- CO2 Sequestration and Geologic Interactions
- Catalytic Processes in Materials Science
- Planetary Science and Exploration
- Nuclear and radioactivity studies
- Isotope Analysis in Ecology
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2008-2025
Idom (Spain)
2023
Universidad Complutense de Madrid
2008-2022
Unidades Centrales Científico-Técnicas
2007
This work presents a detailed study of hyperstoichiometric UO2+x (0 < x 0.25) oxides and an assessment the structural evolution taking place as oxidation proceeds. For this purpose, different powder samples with controlled degree non-stoichiometry have been identified by thermogravimetric analysis characterized X-ray diffraction (XRD) Raman spectroscopy. XRD reflects that commonly assumed Vegard's law is not applicable over whole hyperstoichiometry range, since slight increase lattice...
Abstract In this work, Raman spectroscopy (RS) has been used to study the behavior of spent nuclear fuel (SNF) under disposal conditions. particular, evolutionary Accident-Tolerant Fuels (ATFs) consisting in UO 2 doped with Cr and Cr/Al; as well neutron absorbers (UO Gd), manufactured studied. The prepared pellets have exposed three different pH leachants (inert media, carbonated young cement water calcium) for distinct times. RS analyses conducted both leached unleached pellets. results...
Current necessities of nuclear power plants have led to increase burn-up the fuel during operation. In this context, some undesirable processes, such as a higher release gaseous fission products, may occur. New UO2-based fuels are being developed by adding doping agents. Chromia (Cr2O3) has proved considerably enhance grain growth sintering, and thus promote retention these products. The study Cr-doped UO2 at in situ conditions would allow testing real performance operating conditions....
The rate and extent of the air oxidation UO2 are paramount importance due to its relevance in management spent nuclear fuel at dry storage facilities. In particular, formation U3O8 requires special interest because it could compromise integrity cladding. an attempt reproduce behavior used (in which presence fission products Pu will also influence oxidation), unirradiated was studied this work. is strongly dependent on physical parameters starting material, although some not fully-studied....
Abstract To assess the effect of external γ -radiation on dissolution spent UO 2 fuel matrix, dynamic experiments were performed with pellets using well-controlled flow-through reactor at different low flowrates under oxic conditions. Firstly, setup was validated without radiation leachant compositions ( I = 0.02 mol·L −1 ionic strength and pH from 5.4 to 12.2), (from ~ 4.5 mL·d 120 ), residence times (11.3–383 h) room A good agreement data trends (U concentration vs flowrates) is obtained....
The management of Spent Nuclear Fuel (SNF) comprises different stages in which security is demonstrated. Nevertheless, fundamental research can lead to other design options that must be considered. Currently, one the focuses dry interim storage option, as shortest-term solution until final repositories are available. During this stage, concern oxidation fuel. If UO2 (SNF matrix) exposed air at high-enough temperature, formation U3O8 takes place. larger volume phase could entail stresses on...
SFC is a work package in Eurad that investigates issues related to the properties of spent nuclear fuel back-end cycle. Decay heat, nuclide inventory, and integrity (mechanical otherwise), not least uncertainties, are among primary focal points SFC. These have very significant importance for safety operational aspect back-end. One consequence operation economy back-end, where deeper understanding quantification allow optimization, meaning parts costs can be reduced. In this paper, described,...
The study of uranium oxides at different conditions is paramount importance in the nuclear field, especially regarding characterization spent fuel behavior dry storage scenarios. This paper reports results XRD and Raman analysis on four powdered samples prepared order to cover a specific stoichiometry range UO2+x, i.e. x = 0.24, 0.26, 0.28 0.30. reveal clear increase average tetragonal distortion with oxidation degree, main phase detected for all being weakly identified as U3O7-z (c/a ≪...
Oxidation of spent nuclear fuel (SNF) with undetected cladding defects during dry storage might challenge its integrity if high oxygen-content uranium oxides (U3O8), characterized by a specific volume about 36% higher than UO2's, are formed. As consequence, an accurate characterization the processes involved under anticipated conditions is utmost significance for safety, especially taking into account foreseen lifetime extension dry, interim SNF. Based on extensive survey open literature...
Oxidation of Accident-Tolerant Fuels (ATF) is important from the nuclear safety point view because it could provoke release radioactive material. Despite use ATFs in current reactors, no studies regarding their oxidation are available. Thus, we propose here an experimental study on Cr2O3-doped UO2 samples, which were subjected to a thermal treatment ranging room temperature up 973 K oxidant conditions. The aim assess potential resistance Cr-doped based model systems. Next, effect oxygen...
In this work we have studied, for the first time, oxidation of highly-irradiated Spent Nuclear Fuel (SNF) at in-situ conditions, with a controlled temperature and atmosphere, measuring in same experiment both pellet center rim. The SNF matrix is paramount importance from nuclear fuel safe storage point view, mainly because potential threat that formation oxidized phase U3O8 entails. measurement protocol following conditions (350°C, constant air flow), based on use Raman spectroscopy as...
Abstract In recent years, Raman spectroscopy has been proven to be a highly versatile characterization technique for nuclear materials research. This sensitive possesses, among others, two relevant features that comply with the safety conditions required when handling materials: its flexibility allows remote, in situ and ex analysis, relative ease of use implies small sample quantities limited effort preparation. this work, we present acquisition protocol data processing necessary obtaining...
Abstract The present work analyzes the effect of different Zr contents on microstructure and thermal behavior non-irradiated UO 2 . A set Zr-doped (0, 20, 40, 80, 100 wt%) pellets was prepared via solid-state synthesis by mimicking chemical bonding between ZrO After sintering, monoliths were characterized scanning electron microscopy, Raman spectroscopy, X-ray diffraction. Oxidation samples has been monitored thermogravimetric analysis. Results under air low oxygen partial pressure show a...
The Spanish R&D efforts in dry interim storage of spent nuclear fuel (SNF) are mainly focused on supporting safety under and transportation, including intermediate operations. Major actors involved research entities, academia, the waste management organization industry. Experimental modelling activities carried out to understand predict SNF response prevailing conditions. Particularly, thermal, chemical, mechanical neutronics investigations performed. main outcomes achieved as well outlook...
Abstract In this work, we studied the dehydration process of glycine‐MgSO 4 ·5H 2 O complex under Mars‐relevant conditions (99% CO and 0.6% H ultra violet (UV) irradiation exposure at 7‐mbar pressure high vacuum conditions: 8 × 10 −5 5 mbar) by in situ Raman spectroscopy inside a planetary atmosphere surface chamber (PASC). This work provides quality spectra taken simulated (to be integrated database), as forms part current upcoming NASA ESA Mars missions. The results demonstrate that can...