| Title: |
Enigma of the 'U$_8$Si$_8$O' phase |
| Authors: |
Havette, Julien; Demange, Valérie; Fontaine, Bruno; Halet, Jean-François; Havela, Ladislav; Iltis, Xaviere; Stéphanie, Lamy; Martinez-Celiz, Mayerling; Pasturel, Mathieu |
| Contributors: |
Laboratoire de Caractérisation et d'étude des Propriétés des Combustibles (LCPC); Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E); Département d'Etudes des Combustibles (DEC); Institut de recherche sur les systèmes nucléaires pour la production d'énergie bas carbone (CEA - DES) (IRESNE); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de recherche sur les systèmes nucléaires pour la production d'énergie bas carbone (CEA - DES) (IRESNE); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA); Institut des Sciences Chimiques de Rennes (ISCR); Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes); Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS); Univerzita Karlova Praha, Česká republika = Charles University Prague, Czech Republic = Université Charles Prague, Republique tchèque (UK); Laboratoire de cristallographie et sciences des matériaux (CRISMAT); Université de Caen Normandie (UNICAEN); Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN); Normandie Université (NU)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA); Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN); Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie); Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN); Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS) |
| Source: |
JDA 2024 - 53èmes Journées des Actinides ; https://cea.hal.science/cea-04911635 ; JDA 2024 - 53èmes Journées des Actinides, Apr 2024, Lille, France ; https://jdalille2024.com/ |
| Publisher Information: |
CCSD |
| Publication Year: |
2024 |
| Collection: |
Normandie Université: HAL |
| Subject Terms: |
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] |
| Subject Geographic: |
Lille; France |
| Description: |
International audience ; Using U3Si2 as a nuclear fuel for research and test reactors requires a thorough knowledge of the U-Si phase diagram to predict reliably the in-use fuel behavior. U3Si2 seems to be a perfectly stoichiometric compound. Industrial manufacturers use slightly over-stoichiometric in silicon compositions, to avoid the presence of residual -U or U3Si that affect the irradiation behavior of this fuel. Consequently, a secondary phase with atomic ratio close to 50%U-50%Si is present in the industrial fuel plates. From the binary phase diagram [1], the thermodynamically stable compound is U34Si34.5. Nevertheless, our investigations on both laboratory and industrial samples by electron backscattered diffraction (EBSD) revealed the presence of the tetragonal U34Si34.5 as well as the orthorhombic “U8Si8O” phases in arc-melted samples [2]. The latter was first described as USi [3], but later studies suggested that its stability was achieved only by adding some oxygen in the structure [4]. The presence of light elements (mainly carbon) in metallic uranium may justify the formation of this pseudo-binary phase during the synthesis of Si-rich U3Si2. So why does this “U8Si8X” (X = C, O) phase formation depend on the cooling rate after melting? Why does it decompose upon annealing? To answer these important questions and to understand the phase equilibria in the U-Si system, experimental and theoretical studies were undertaken. On the one hand, phonon calculations predict instability of the binary “USi” at 0 K, but its stabilization if a small amount of C is added. On the other hand, the quantity of “USi” increases with Si-content in rapidly-cooled arc-melted samples, from 41 to 46 at.% Si, and then drops giving way to U34Si34.5, the latter being the only visible phase (aside U3Si2) from 48 at.% Si. It should be noted that U5Si4 was not been observed, except when C was intentionally added (U20Si16C3). A summary of results obtained from various samples we synthesized will be presented, including ab-initio ... |
| Document Type: |
conference object |
| Language: |
English |
| Availability: |
https://cea.hal.science/cea-04911635; https://cea.hal.science/cea-04911635v1/document; https://cea.hal.science/cea-04911635v1/file/JdA24_U8Si8O_MAP.pdf |
| Rights: |
https://about.hal.science/hal-authorisation-v1/ ; info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.C3C2B3A7 |
| Database: |
BASE |