Effect of Water Chemistry on the Performance of Alloy 800H in Supercritical Water-cooled Reactor
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摘要: 为研究超临界水环境下温度、溶解氧等水化学因素对于堆内包壳材料服役性能的影响规律，探究超临界水冷堆的水化学控制策略，以800H合金作为实验材料，测量了不同温度、水化学条件下超临界水中材料的腐蚀增重规律和慢应变速率拉伸曲线。温度的提升将加快800H合金的腐蚀速率，腐蚀激活能约为159 kJ/mol；温度由550℃升高至650℃，材料的屈服强度变化不显著，约为175 MPa，但屈强比显著下降，呈现明显的软化趋势；650℃下溶解氧浓度由0 μg·kg–1提升至500 μg·kg–1，导致腐蚀增重量增加约30%，而使用联氨除氧的水化学控制方法可以降低800H合金的腐蚀速率；溶解氧浓度对于慢应变速率拉伸的测试结果并无明显作用，这主要是由于超临界水环境下材料的应力腐蚀失效由蠕变过程主导。研究结果表明超临界水环境下进行温度和溶氧控制有助于降低800H合金的腐蚀速率并保持其力学性能。Abstract: In order to study the influence of water chemistry factors such as temperature and dissolved oxygen on the service performance of cladding materials in supercritical water environment, and to find out the water chemistry control policy of supercritical water-cooled reactor, Alloy 800H was used as the experimental material in this paper, and the corrosion weight gain and slow strain rate tensile curve of the material in supercritical water under different temperature and water chemistry conditions were measured. Increasing the temperature would accelerate the corrosion rate of Alloy 800H, and the corrosion activation energy was about 159 kJ/mol. Increasing the temperature from 550℃ to 650℃, the yield strength of the material did not change significantly, which was about 175 MPa. However, the ratio of yield strength over tensile strength decreased significantly, showing an obvious softness trend of the material. At 650℃, raising the dissolved oxygen concentration from 0 μg·kg–1 to 500 μg·kg–1 resulted in an increase of corrosion weight gain of about 30%, but the water chemistry control method using hydrazine deoxygenation could reduce the corrosion rate of Alloy 800H. The dissolved oxygen concentration did not have a significant effect on the results of slow strain rate tensile testing, mainly because the stress corrosion failure of the material in supercritical water environment is dominated by creep process. The results indicate that appropriate controlling of temperature and dissolved oxygen in supercritical water environment can be helpful to reduce the corrosion rate of Alloy 800H and maintain its mechanical properties.
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Key words:
- Supercritical water-cooled reactor /
- Alloy 800H /
- Water chemistry /
- Stress corrosion
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图 2 SSRT样品及均匀腐蚀样品尺寸 mm
Figure 2. Dimensions of Samples for SSRT Test and Corrosion Test
图 3 样品腐蚀增重曲线及拟合结果
W—单位面积的腐蚀增重量，mg/dm2；t—浸泡时间，h
Figure 3. Corrosion Weight Gain Curves for Sample and Fitting Results
图 4 不同水化学条件下样品浸泡100 h的腐蚀增重量
Figure 4. Wight Gain of Samples under Different Water Chemistry Conditions for 100 h Exposure
图 5 样品在650℃氩气除氧环境中浸泡500 h的腐蚀形貌
Figure 5. Surface Morphology of Samples after 500 h Exposure in Deaerated SCW at 650°C
图 6 研磨样品STEM-EDS面扫结果
Figure 6. STEM-EDS Mapping on the Cross Section of Ground Samples
图 7 不同水化学工况的腐蚀表面形貌
Figure 7. Surface Morphology of Samples under Different Water Chemistry Conditions
图 8 金属氧化物形成所需氧分压
Figure 8. Oxygen Partial Pressure Required for the Formation of Metal Oxide
图 10 样品在不同水化学条件下的SSRT曲线
Figure 10. SSRT Curves of Samplens under Different Water Chemistry Conditions
图 11 2种工况下的SSRT样品表面形貌
Figure 11. Surface Morphology of SSRT Sample under Two Conditions
图 12 氧化工况下SSRT样品的截面EBSD图
Figure 12. EBSD Mapping on Cross Section of SSRT Sample under Oxidation Condition
表 1 800H合金的化学成分
Table 1. Chemical Composition of Alloy 800H
元素 Fe Cr Ni Al Ti Mn Si C 质量分数/% Bal. 21.280 31.660 0.541 0.426 0.660 0.303 0.077 “Bal.”—Fe元素的占比余量 
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表 2 水化学测试环境参数
Table 2. Parameters of Water Chemistry Test
环境条件 入口溶解氧浓度/(μg·kg−1) 联氨浓度/(μg·kg−1) 水质 中性工况 <5 超纯水 氧化工况 300 超纯水 氧加联氨 300 100 pH25=8.1 过量联氨 <5 100 pH25=8.1
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