Skip to Main content Skip to Navigation
Conference papers

What does the crystallo-chemistry of UO$_2$ tells us to design innovative nuclear fuels?

Abstract : Nuclear fuel plays a fundamental role in the design of innovative nuclear systems. At the beginning of nuclear area, designers chose UO$_2$ as nuclear fuel because they thought it was a stable compound with no structural changes in operating conditions. Contrarily to these pioneer ideas, recent results evidenced that UO$_2$ has some internal degrees of disorder appearing when UO$_2$ is heated, or chemically doped. Here we are interested in understanding UO$_2$ disorder in order to derive driving force for the design of innovative nuclear fuels. First, when UO$_2$ is heated, the thermal motion of oxygen becomes anharmonic. Using neutron pair distribution function (PDF), we proved that this disorder could be modelled by a low symmetry local order different from average order. The existence of low symmetry domains could explain the increase of UO$_2$ heat capacity at high temperature, which is a factor increasing its resistance to irradiation damage.Second, when UO$_2$ is chemically doped, either by oxygen or by lanthanide fission products, the doping element is not homogenously distributed in the UO$_2$ crystalline lattice. In the case of oxidation, interstitial oxygen atoms are encapsulated in some clusters named cuboctahedrons [2]. In the case of neodymium doped UO$_2$, a miscibility gap having chemical phases with different Nd contents appears in the hypo-stoichiometric domain [3]. The manner by which UO$_2$ can retain radioactive fission products is closely related to the manner by which some chemical elements can be caged in UO$_2$. Therefore, these recent results evidence that the existence of disorder in UO$_2$ can be beneficial for irradiation resistance and radionuclide retention. Understanding of this disorder is underway, but its existence is already a driving force for the design of innovative nuclear fuel. The design of such fuels should include some degrees of freedom to accommodate irradiation effects and changes in chemical composition.
Complete list of metadatas

https://hal-cea.archives-ouvertes.fr/cea-02614151
Contributor : Bibliothèque Cadarache <>
Submitted on : Wednesday, May 20, 2020 - 4:48:22 PM
Last modification on : Friday, May 29, 2020 - 3:12:31 AM

File

201900002218.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : cea-02614151, version 1

Collections

CEA | DEN

Citation

L. Desgranges. What does the crystallo-chemistry of UO$_2$ tells us to design innovative nuclear fuels?. IUPAC 2019 - The 47th World Chemistry Congress, Jul 2019, Paris, France. ⟨cea-02614151⟩

Share

Metrics

Record views

11

Files downloads

11