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本文用示踪原子法测得了高于1915℃的二氧化铀表面扩散系数。在数学模型中,考虑了体扩散和气相扩散效应。在1760—2110℃间UO_2的表面扩散系数可以表示为D_(?)=1.41×10~8exp(-123.6/RT)cm~2/s。关于气氛分子对二氧化铀表面扩散的影响作了实验和理论的探讨。结果表明UO_2的表面扩散系数随气氛分子质量的平方根线性减少。在1811—1818℃间可以表示为D_(?)=-9.86×10~(-7) M~(1/2)+2.05×10~(-5)cm~2/s。这可能与气氛分子对扩散表面的无规则碰撞所造成的扩散阻力有关。
In this paper, the surface diffusion coefficient of uranium dioxide above 1915 ℃ was measured by tracer atomic method. In the mathematical model, the effects of volume diffusion and vapor diffusion are considered. The surface diffusion coefficient of UO_2 at 1760-2110 ℃ can be expressed as D _ (?) = 1.41 × 10 ~ 8exp (-123.6 / RT) cm ~ 2 / s. The influence of atmosphere molecules on the surface diffusion of uranium dioxide was discussed experimentally and theoretically. The results show that the surface diffusion coefficient of UO 2 decreases linearly with the square root of the molecular mass of the atmosphere. It can be expressed as D _ (?) = - 9.86 × 10 ~ (-7) M ~ (1/2) + 2.05 × 10 ~ (-5) cm ~ 2 / s at 1811-1818 ℃. This may be related to the diffusion resistance caused by the atmospheric molecules’ random collision with the diffusion surface.