U $_3$ Si $_2$在蒸汽腐蚀过程中的结构和相演变
Structural and phase evolution in U$_3$Si$_2$ during steam corrosion
摘要：
用中子原位衍射方法研究了铀$_3$硅$_2$核燃料在氘水蒸汽中的腐蚀。密度泛函理论与严格的热力学描述的氢化物，包括气体/固体熵的贡献。H在U $_3$ Si $_2$ H $_x$的2 $b$间隙位点吸收，并移动到$x\ge 0.5$的8 $j$。氢化力晶格膨胀和$a/c$比率的变化与位点偏好有关。Rietveld细化跟踪了350-500 °C下的腐蚀反应，并优先选择8 j位点。高于375 °C时，在晶界和体相中形成UO $_2$、U $_3$ Si $_5$和USi $_3$。氢化发生在本体中并且先于其他反应。
英文摘要：
U$_3$Si$_2$ nuclear fuel is corroded in deuterated steam with in situ neutron diffraction. Density functional theory is coupled with rigorous thermodynamic description of the hydride including gas/solid entropy contributions. H absorbs in the 2$b$ interstitial site of U$_3$Si$_2$H$_x$ and moves to 8$j$ for $x\ge 0.5$. Hydriding forces lattice expansion and change in $a/c$ ratio linked to site preference. Rietveld refinement tracks the corrosion reactions at 350-500 °C and preference for the 8j site. Above 375 °C, formation of UO$_2$, U$_3$Si$_5$ and USi$_3$ take place in the grain boundaries and bulk. Hydriding occurs in bulk and precedes other reactions.
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