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31.
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Here we present a long-term nonisothermal reactive transport model for the interactions of the corrosion products of a carbon-steel canister and the compacted bentonite of the engineered barrier of a high-level radioactive waste repository in granite. Canister corrosion causes an increase in the pH and the concentration of dissolved Fe2+ of the bentonite porewater. Iron precipitates as magnetite and siderite and sorbs via cation exchange and surface complexation on weak sites. Magnetite precipitation reduces significantly the porosity of the bentonite near the canister. The thickness of the zone of reduced porosity is 7 cm at t = 1 Ma. This thickness increases significantly when the dependence of the corrosion rate on the chemical conditions is considered and decreases 3 cm when smectite dissolution and analcime precipitation are taken into account. Model results are not significantly sensitive to the thermal transient and the effect of temperature on the corrosion rate. The conclusions of our simulations are consistent for the most part with those reported by others for engineered barrier systems at similar chemical conditions. 相似文献
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Artificial neural networks and their application to assessment of ultimate strength of plates with pitting corrosion 总被引:1,自引:0,他引:1
The potential for the structural capability degrading effects of both corrosion and fatigue induced cracks are of profound importance and must be both fully understood and reflected in vessel's inspection and maintenance programme. Corrosion has been studied and quantified by many researchers, however its effect on structural integrity is still subject to uncertainty, particularly with regards to localized corrosion. The present study is focused on assessing the effects of localized pitting corrosion on the ultimate strength of unstiffened plates. Over 265 non-linear finite-element analyses of panels with various locations and sizes of pitting corrosion have been carried out. The results indicate that the length, breadth and depth of pit corrosion have weakening effects on the ultimate strength of the plates while plate slenderness has only marginal effect on strength reduction. Transverse location of pit corrosion is also an important factor determining the amount of strength reduction. When corrosion spreads transversely on both edges, it has the most deteriorating effect on strength. In addition, artificial neural network (ANN) method is applied to derive a formula to predict ultimate strength reduction of locally corroded plates. It is found out that the proposed formulae can accurately predict the ultimate strength of locally corroded plates under uniaxial in-plane compression. 相似文献
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海藻组分抑制乙酰胆碱酯酶活性研究 总被引:12,自引:0,他引:12
采用乙酰胆碱酯酶抑制剂活性筛选模型对采自青岛沿海的22种海藻样品提取物的石油醚组分和乙酸乙酯组分进行了活性筛选.结果表明,22种海藻的石油醚组分均具有不同程度的乙酰胆碱酯酶抑制活性,其中亮管藻、海头红、鸭毛藻和孔石莼表现出较强的活性,在浓度为50μg/ml时的抑制率均大于50.0%,分别为50.5%、55.5%、56.6%和65.8%;其他大部分海藻的抑制率在30.1%到48.9%之间.与石油醚组分不同的是,只有少数海藻的乙酸乙酯组分表现出乙酰胆碱酯酶抑制活性,其中鸭毛藻的活性最为显著,在浓度为25μg/ml时抑制率高达71.8%;孔石莼的乙酸乙酯组分也具有较强的抑制活性;其余海藻的乙酸乙酯组分对乙酰胆碱酯酶的抑制活性较弱,有些不仅没有活性,反而表现出不同程度的增强作用. 相似文献
37.
钢在海洋沉积物中的腐蚀电化学测量技术 总被引:2,自引:1,他引:1
1998年3月在中国科学院海洋研究所设计了一个新型电解池,以满足试样在海洋沉积物中极化曲线测量的需要。该电解池装有二个参比电极,它们距工作电极之间的距离可以精确调节。介质电阻对极化曲线的影响可以计算不同电位下的介质电阻予以消除,模拟电路和实际体系的测量结果表明,该实验技术可以用于海洋沉积物腐蚀电化学的研究中。 相似文献
38.
大布苏湖东岸“狼牙棒”地形成因探讨 总被引:1,自引:1,他引:1
经野外实地勘查研究,并采取土样进行易溶盐、孢粉分析,结合地貌形态特征与化验成果进行研究论证,认为“狼牙棒”地形的形成与其特殊的岩性条件和内、外动力地质作用相关,对“狼牙棒”地形形成机理进行探讨。 相似文献
39.
The present study investigates the alteration of a fractured glass block in contact with iron and Callovo-Oxfordian claystone at 90 °C under anoxic and water-saturated conditions. The alteration rates and the nature of glass alteration products at the different compact interfaces (glass-clay, glass-iron) and in cracks were assessed by solution chemistry and microscopic-scale techniques (scanning electron microscopy coupled with energy-dispersive X-ray microscopy, microRaman spectroscopy, and X-ray absorption fine structure spectroscopy). A significant but modest (two-fold) increase in glass alteration in contact with steel was observed, leading to an average alteration rate over the experiment of about 0.007–0.014 g/m2/d. This rate is significantly lower than forward rate r0 in clay-equilibrated groundwater (1.7 g/m2/d), indicating that a decrease of the alteration rate was not hindered by the steel presence. The corrosion–alteration interface was made up of successive layers of corrosion products in contact with iron, a layer of Fe silicates, and an altered glass layer enriched in Fe. Characterization of the glass block in direct contact with claystone revealed that the thickness of altered glass was much more important than at the glass-iron interface. The altered glass layer in contact with clay was slightly enriched in Fe and Mg, and depleted in alkali cations. Altered glass layers in cracks were usually limited to fringes thinner than 2 μm, with a thickness decreasing from the crack mouth, indicating that alteration is controlled by transport in the cracks. The fractures were partially filled with calcite and lanthanide hydroxocarbonate precipitates. These results contribute to the understanding of nuclear vitrified waste-iron-corrosion products interactions in a deep geological repository. 相似文献
40.
Bacteria,fungi and biokarst in Lechuguilla Cave,Carlsbad Caverns National Park,New Mexico 总被引:4,自引:0,他引:4
K. I. Cunningham D. E. Northup R. M. Pollastro W. G. Wright E. J. LaRock 《Environmental Geology》1995,25(1):2-8
Lechuguilla Cave is a deep, extensive, gypsumand sulfur-bearing hypogenic cave in Carlsbad Caverns National Park, New Mexico, most of which (>90%) lies more than 300 m beneath the entrance. Located in the arid Guadalupe Mountains, Lechuguilla's remarkable state of preservation is partially due to the locally continuous Yates Formation siltstone that has effectively diverted most vadose water away from the cave. Allocthonous organic input to the cave is therefore very limited, but bacterial and fungal colonization is relatively extensive: (1)Aspergillus sp. fungi and unidentified bacteria are associated with iron-, manganese-, and sulfur-rich encrustations on calcitic folia near the suspected water table 466 m below the entrance; (2) 92 species of fungi in 19 genera have been identified throughout the cave in oligotrophic (nutrient-poor) soils and pools; (3) cave-air condensate contains unidentified microbes; (4) indigenous chemoheterotrophicSeliberius andCaulobacter bacteria are known from remote pool sites; and (5) at least four genera of heterotrophic bacteria with population densities near 5×105 colony-forming units (CFU) per gram are present in ceiling-bound deposits of supposedly abiogenic condensation-corrosion residues. Various lines of evidence suggest that autotrophic bacteria are present in the ceiling-bound residues and could act as primary producers in a unique subterranean microbial food chain. The suspected autotrophic bacteria are probably chemolithoautotrophic (CLA), utilizing trace iron, manganese, or sulfur in the limestone and dolomitic bedrock to mechanically (and possibly biochemically) erode the substrate to produce residual floor deposits. Because other major sources of organic matter have not been detected, we suggest that these CLA bacteria are providing requisite organic matter to the known heterotrophic bacteria and fungi in the residues. The cavewide bacterial and fungal distribution, the large volumes of corrosion residues, and the presence of ancient bacterial filaments in unusual calcite speleothems (biothems) attest to the apparent longevity of microbial occupation in this cave. 相似文献