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首页> 外文会议>Thirteenth International Symposium on Zirconium in the Nuclear Industry; Jun 10-14, 2001; Annecy, France >Test Reactor Studies of the Shadow Corrosion Phenomenon
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Test Reactor Studies of the Shadow Corrosion Phenomenon

机译：阴影腐蚀现象的试验反应器研究

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摘要

The shadow effect, resulting in enhanced corrosion on zirconium-base alloys in proximity to other metal, has been observed since the 1960s. In 1997, hot-cell examinations revealed thick oxide layers on fuel cladding surfaces that during irradiation had been located in the shadow of Inconel spacer grids. The acronym ESSC (Enhanced spacer shadow corrosion) was used to describe the phenomenon. Following the observation of ESSC, several investigations were initiated to develop an explanation of the shadow corrosion phenomenon. In this paper, results are presented and compared from in-reactor experiments performed in three different test reactors, the R2 reactor in Studsvik, the MITR-II reactor at MIT, and the Halden test reactor. The first study, performed in Studsvik, was initiated to assess the feasibility of studying the shadow corrosion phenomenon during relatively short irradiation periods in a test reactor. The results clearly showed that a shadow was formed on Zircaloy cladding in contact with Inconel within 34 days of exposure in the center of the core, while no shadow was observed on specimens situated outside and upstream from the core. The test at MIT was initiated to identify the basic mechanisms of the shadow effect. The MIT research reactor MITR-II was used to simulate BWR core coolant conditions. A sample train included Zircaloy-2 claddings with different counter materials surrounding each clad specimen. The counter materials were intended to serve as the materials tentatively producing shadow corrosion when located in close proximity to the clad specimens. The counter materials chosen were strong or weak beta emitters, platinum, inert material (zirconia), Inconel X-750, coated Inconel X-750, and Zircaloy-2 at various separation distances. The results showed that beta radiation from the counter material is not the main mechanism for the shadow effect, that a coating on the counter material inhibits the formation of shadow corrosion, and that shadow corrosion is dominated by a mechanism of electrochemical character. Shadow corrosion was observed on samples situated outside and downstream from the core. This observation in combination with the results from the test in the R2 reactor imply that radiolysis has an important role for the formation of shadow corrosion. Two separate tests were performed in the Halden test reactor. The first test was focused on evaluating the effect of variations in clad chemical composition and heat treatments as well as type of counter material. The considered clad materials included Zircaloy-2 with varied average secondary phase particle size as well as a Zircaloy-2 base material. The Zircaloy-2 base material has a chemical composition similar to but outside the range specified for Zircaloy-2. The counter materials included Inconel as well as two different variants of zirconium-based alloys. The second test in Halden was dedicated to study the effect of the clad surface treatment, covering a matrix of ground and pickled outer surfaces in combination with treatments resulting in oxide layers of three different thicknesses, from as-fabricated to 2 μm.
机译：自1960年代以来，就一直观察到阴影效应，导致对锆基合金附近其他金属的腐蚀增强。 1997年，热室检查发现燃料包壳表面的氧化层很厚，在辐照过程中，氧化层位于Inconel隔栅的阴影中。首字母缩写词ESSC（增强的垫片阴影腐蚀）用于描述该现象。在观察了ESSC之后，开始了数项研究以解释阴影腐蚀现象。本文介绍了在三个不同的试验反应堆中进行的反应堆内实验的结果，并将它们进行了比较，这些试验堆分别位于Studsvik的R2反应堆，MIT的MITR-II反应堆和Halden试验反应堆。在Studsvik进行的第一项研究是为了评估在相对较短的辐射时间内在试验堆中研究阴影腐蚀现象的可行性。结果清楚地表明，在暴露于铁心中心的34天内，与Inconel接触的Zircaloy覆层上形成了阴影，而在铁心外部和上游的样品上未观察到阴影。麻省理工学院的测试旨在确定阴影效应的基本机制。 MIT研究堆MITR-II用于模拟BWR堆芯冷却液条件。样本列车包括Zircaloy-2覆层，每个覆层样品周围都有不同的计数材料。相对材料旨在用作紧贴包层试样时会产生阴影腐蚀的材料。选择的抗衡材料是强或弱的β发射体，铂，惰性材料（氧化锆），Inconel X-750，镀膜的Inconel X-750和Zircaloy-2，且间距不同。结果表明，来自对位材料的β辐射不是产生阴影效应的主要机理，对位材料上的涂层抑制了阴影腐蚀的形成，而阴影腐蚀则受电化学特性的影响。在岩心外部和下游的样品上观察到阴影腐蚀。该观察结果与R2反应器中的测试结果相结合，表明辐射分解对于阴影腐蚀的形成具有重要作用。在Halden测试反应器中进行了两个单独的测试。第一个测试的重点是评估复合化学成分和热处理以及对接材料类型的变化所产生的影响。所考虑的包层材料包括具有变化的平均第二相粒度的Zircaloy-2，以及Zircaloy-2基础材料。 Zircaloy-2基材的化学成分与Zircaloy-2相似，但超出了规定范围。柜台材料包括Inconel以及两种不同的锆基合金。 Halden的第二项测试致力于研究复合表面处理的效果，该复合表面覆盖了地面和酸洗的外表面，并结合处理产生了三种不同厚度的氧化物层（从制造到2μm）。

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