Thermodynamic simulation of phase equilibria in the UO2-Gd2O3 system at high temperatures

Popov, S. G.; Лысенко, В. А.; Proselkov, V. N.

doi:10.1134/s0018151x12020137

Cited by 2 publications

(2 citation statements)

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“…Other thoroughly investigated consequences of adding gadolinia to UO 2 (in solid solution) include the reduction of fissile material from the assembly (as gadolinia displaces UO 2 ), a reduction in melting temperature of the fuel [3] and the significant degradation in thermal conductivity that the solid solution has in comparison with the fresh UO 2 material [4] (which also undergoes a significant reduction in thermal conductivity due to burnup effects [5]). Consequently, nuclear fuel manufacturers have pursued alternative burnable absorbing technologies: of note is the Integral Fuel Burnable Absorber (IFBA) technology developed by Westinghouse Electric Company using ZrB 2 [2,6,7].…”

Section: Burnable Absorbersmentioning

confidence: 99%

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Defect evolution in burnable absorber candidate material: Uranium diboride, UB2

Burr¹,

Kardoulaki²,

Holmes³

et al. 2019

Journal of Nuclear Materials

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The stability, diffusivity and clustering behaviour of defects in uranium diboride (UB 2) was investigated in light of the potential application as a burnable absorber in nuclear fuel. UB 2 was found to accommodate limited deviations from stoichiometry, which should be a consideration when manufacturing and operating the material. Self-diffusivity of both U and B was found to be sluggish (10 −14 cm 2 /s for B and 10 −19 cm 2 /s for U at 2000 K) and highly anisotropic, with migration along the basal planes being orders of magnitude faster than c-axis migration. The anisotropy of defect migration (both interstitials and vacancies) is predicted to hinder recombination of defects produced by collision cascades, thus limiting the radiation tolerance of the material. Boron and uranium vacancies exhibit a drive to cluster. Boron vacancies in particular, which are mobile on basal planes, are predicted to cluster into strongly bound di-vacancy, which in turn are less mobile. These are then predicted to grow into larger two-dimensional vacancy clusters on the B plane, leading to anisotropic swelling. We provide an analytical expression to predict the stability of these clusters based on purely geometrical considerations. Finally, the accommodation of Li, He and Xe onto vacancy clusters was considered. Li appears to stabilise the structure upon U depletion, while the retention of He and Xe appears to rise with increasing B depletion, through the formation of vacancy clusters.

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