Hydriding kinetics of thin sponge-Zr layers metallurgically bonded to a Zircaloy disk has been studied by thermogravimetry in the temperature range 350-400 degrees C in 7 MPa hydrogen-steam mixtures. Some specimens were prefilmed with a thin oxide layer prior to exposure to the reactant gas; all were coated with a thin layer of gold to avoid premature reaction at edges. Two types of hydriding were observed in prefilmed specimens, viz., a slow hydrogen absorption process that precedes an accelerated (massive) hydriding. At 7 MPa total pressure, the critical ratio of H-2/H2O above which massive hydriding occurs at 400 degrees C is similar to 200. The critical H-2/H2O ratio is shifted to similar to 2.5 x 10(3) at 350 degrees C. The slow hydriding process occurs only when conditions for hydriding and oxidation are approximately equally favorable. Based on maximum weight gain, the specimen is completely converted to delta-ZrH2 by massive hydriding, in similar to 5 h at a hydriding rate of similar to 10(-6) mol H/cm(2) s. Incubation times of 10-20 h prior to the onset of massive hydriding increases with prefilm oxide thickness in the range of 0-10 mu m. By changing to a steam-enriched gas, massive hydriding that initially started in a steam-starved condition was arrested by re-formation of a protective oxide scale, (C) 1997 Elsevier Science B.V. [References: 23]
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机译：已经通过热重法在温度范围为350-400摄氏度，温度为7 MPa的氢蒸汽混合物中研究了冶金结合到Zircaloy圆盘上的海绵Zr薄层的氢化动力学。一些样品在暴露于反应气体之前先用薄的氧化物层预成膜。全部都涂有一层薄薄的金，以避免边缘过早反应。在预成膜的样品中观察到两种类型的氢化，即在加速（大量）氢化之前的缓慢氢吸收过程。在7 MPa的总压力下，H-2 / H2O的临界比率在400摄氏度以上发生大规模氢化。该临界比率类似于200。350的H-2 / H2O临界比率在350处近似于2.5 x 10（3）。仅在氢化和氧化条件大致相同时才发生缓慢氢化过程。基于最大的重量增加，通过大规模氢化将样品完全转化为delta-ZrH2，类似于5 h，氢化速率类似于10（-6）mol H / cm（2）s。大量氢化开始之前的10-20小时孵育时间会随着预膜氧化物厚度在0-10微米范围内而增加。通过改用富含蒸汽的气体，最初在缺乏蒸汽的条件下开始的大量氢化作用因保护氧化物垢的重新形成而被制止，（C）1997 Elsevier Science B.V. [参考文献：23]
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