Atomistic modelling of iodine-oxygen interactions in strained sub-oxides of zirconium
Atomistic modelling of iodine-oxygen interactions in strained sub-oxides of zirconium
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DOI：
10.1016/j.jnucmat.2021.153394
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发表时间：
2021-11
影响因子：
3.1
通讯作者：
V. Podgurschi;D. King;J. Smutná;J. Kermode;M. Wenman
中科院分区：
文献类型：
--
作者：
V. Podgurschi;D. King;J. Smutná;J. Kermode;M. Wenman
在水反应堆中，碘应力腐蚀开裂被认为是芯块-包壳相互作用失效的原因，但其机理和化学性质仍有争议，氧的保护作用也不清楚。采用密度泛函理论计算研究了在施加静液压应变（− 2%至+ 3%）下碘和氧与体相和表面Zr的相互作用，以模拟Zr到ZrO 2的裂纹尖端条件，使用各种中间低价氧化物（Zr 6 O，Zr 3 O，Zr 2 O和ZrO）。的形成能量的碘八面体间隙在Zr被发现随着流体静力学应变的增加而减少，而碘替代缺陷的能量被发现是相对不敏感的应变。随着氧含量的增加，碘间隙的形成能从1.03 eV增加到8.61 eV，支持氧具有保护作用的观点。与此同时，+3%的拉伸流体静力应变导致碘间隙形成能在具有较高氧含量的结构中降低更多：与纯Zr的1.47 eV降低相比，ZrO中的4.56 eV降低。在氧存在下，碘的取代能和间隙能与碘的吸附能的比较表明，碘在Zr位点上的取代能对所有菌株更有利，甚至间隙碘在+1-5%的菌株之间也是有利的。虽然取代缺陷是优选的八面体间隙缺陷，在有序的低氧化物，3%的拉伸应变显着缩小的能隙和更高的应变可能会导致间隙缺陷的形成。
In water reactors, iodine stress corrosion cracking is considered the cause of pellet-cladding interaction failures, but the mechanism and chemistry are debated and the protective effect of oxygen is not understood. Density functional theory calculations were used to investigate the interaction of iodine and oxygen with bulk and surface Zr under applied hydrostatic strain (− 2% to+ 3%) to simulate crack tip conditions in Zr to ZrO 2, using a variety of intermediate suboxides (Zr 6 O, Zr 3 O, Zr 2 O and ZrO). The formation energy of an iodine octahedral interstitial in Zr was found to decrease with increasing hydrostatic strain, whilst the energy of an iodine substitutional defect was found to be relatively insensitive to strain. As the oxygen content increased, the formation energy of an iodine interstitial increased from 1.03 eV to 8.61 eV supporting the idea that oxygen has a protective effect. At the same time, a+ 3% tensile hydrostatic strain caused the iodine interstitial formation energy to decrease more in structures with higher oxygen content: 4.56 eV decrease in ZrO compared to 1.47 eV decrease for pure Zr. Comparison of the substitutional and interstitial energies of iodine, to the adsorption energy of iodine, in the presence of oxygen, shows the substitutional energy of iodine onto a Zr site is more favourable for all strains and even interstitial iodine is favourable between strains of+ 1-5%. Although substitutional defects are preferred to octahedral interstitial defects, in the ordered suboxides, a 3% tensile strain significantly narrows the energy gap and higher strains could cause interstitial defects to form.