Electron Enrgy-Dependent Type of Dislocation Loops in CeO&lt;SUB&gt;2&lt;/SUB&gt;

和史, 安永; Yasunaga, Kōjirō; Yasuda, Kazuhiro; 和弘, 安田; 謙一, 椎山; Kenichi, Shiiyama; 晶, 松村; Matsumura, Shuichi; 健, 園田; Sonoda, Tatsuhiko

doi:10.2320/materia.47.612

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“…Consistent with our results, this suggests that damage accumulation in this reducible material is driven by concurrent cation valence changes and anion-specific Frenkel pair formation, a process distinct from that of nonreducible ThO 2 . Similar oxygen-selective point defect production has been observed in CeO 2 irradiated with electrons [36][37][38] , which deposit energy through isolated electron excitation, confirming that the formation of these ion tracks is an effect of ionization. In this work, clusters of interstitial oxygen were observed, indicating that anions preferentially displaced by ionizing radiation tend to aggregate in planar interstitial dislocation loops 37 , which have been identified as a possible cause of problematic microstructure changes in the rim region of nuclear fuel pellets 22 .…”

Section: Resultssupporting

confidence: 60%

Redox response of actinide materials to highly ionizing radiation

et al. 2015

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Energetic radiation can cause dramatic changes in the physical and chemical properties of actinide materials, degrading their performance in fission-based energy systems. As advanced nuclear fuels and wasteforms are developed, fundamental understanding of the processes controlling radiation damage accumulation is necessary. Here we report oxidation state reduction of actinide and analogue elements caused by high-energy, heavy ion irradiation and demonstrate coupling of this redox behaviour with structural modifications. ThO 2 , in which thorium is stable only in a tetravalent state, exhibits damage accumulation processes distinct from those of multivalent cation compounds CeO 2 (Ce 3 þ and Ce 4 þ ) and UO 3 (U 4 þ , U 5 þ and U 6 þ ). The radiation tolerance of these materials depends on the efficiency of this redox reaction, such that damage can be inhibited by altering grain size and cation valence variability. Thus, the redox behaviour of actinide materials is important for the design of nuclear fuels and the prediction of their performance.

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