Waste Package Performance Evaluations for the Proposed High-Level Nuclear Waste Repository at Yucca Mountain

The evaluation studies of the proposed repository for long-term storage of spent nuclear fuel and high-level nuclear waste at Yucca Mountain, Nevada, are underway. Fulfillment of the requirements for limiting dose to the public, which includes containment of the radioactive waste emplaced in the proposed repository and subsequent slow release of radionuclides from the Engineered Barrier System (EBS) into the geosphere, will rely on a robust waste container design, among other EBS components. Part of the evaluation process involves sensitivity studies aimed at elucidating which model parameters contribute most to the waste package and overlying drip shield degradation characteristics. The model parameters identified for this study include (1) general corrosion rate parameters and (2) stress corrosion cracking (SCC) parameters. Temperature dependence and parameter uncertainty are evaluated for the general corrosion rate model parameters while for the SCC model parameters, uncertainty treatment of stress intensity factor, crack initiation threshold, and manufacturing flaw orientations are evaluated. Based on these evaluations new uncertainty distributions are generated and recommended for future analyses. Also, early waste package failures due to improper heat treatment were added to the waste package degradation model. The results of these investigations indicate that the waste package failure profiles are governed by the manufacturing flaw orientation model parameters.     

000Cr30Mo2钢焊后耐碱蚀性能研究

本文研究了高纯度000Cr30Mo2钢的钨极氩弧焊工艺和氩气延续保护方法。测试焊接接头的机械性能来试验其在内蒙古天然碱苛化烧碱液中的耐蚀性能。用光镜和电镜观察焊接接头区的金相组织,断口形貌特征和断裂性质,分析腐蚀试样的腐蚀形态及化学成分变化,鉴定了钝化膜形貌和结构。结果表明:用钨极氩弧焊和氩气延续保护的焊接方法,焊接接头可以获得较满意的焊缝质量和机械性能,在天然碱苛化烧碱液中有较好的耐腐蚀性能。     

离子注入航空轴承延寿应用研究

航空轴承的使用寿命普遍较短。通过大量数据统计分析和失效轴承进一步研究,发现航空轴承使用中存在的主要问题是腐蚀和磨损。经离子注入航空轴承材料的各种试验表明,试验材料表面产生了非晶态物质,其耐腐蚀性能显著提高,耐磨性提高两倍以上。同时,针对离子注入航空轴承而研制的离子束多功能机,解决了球面无法均匀注入的难题。经离子注入的航空轴承,目前在航空发动机中得到较广泛的应用,不仅顺利通过了工厂台架试车和地面燃机试验,而且所发往空军使用的航空轴承到目前为止,均表现良好。     

NR 油田油井井筒腐蚀影响因素实验研究

针对NR 油田油井井筒腐蚀日益严重的问题,展开了产出水对油井井筒腐蚀原因及影响因素实验研究。采用 了静态挂片法,以典型井产出水为研究对象,系统研究产出水在不同腐蚀时间、pH 值、CO2 浓度、H2S 浓度条件下对腐 蚀速率的影响,应用正交实验研究这几种因素对腐蚀速率的影响程度。实验结果表明,腐蚀反应时间在24 h 时腐蚀速 率达到最大,超过24 h 后随着时间延长腐蚀速率慢慢降低,当超过72 h 时腐蚀速率基本不变。温度越高,产出水对挂 片腐蚀越严重,挂片为均匀腐蚀,随温度逐渐升高,腐蚀产物由黄色变成黑色,棕红色的溶液中含有暗红色絮状沉淀; 在65 ℃时,pH 值越低的产出水对挂片腐蚀速率影响越大,产出水中H2S 浓度与CO2 浓度对挂片腐蚀速率影响相当, 由正交实验确定了腐蚀速率影响程度大小顺序,依次为温度、pH 值、H2S 浓度、CO2 浓度,与单因素影响实验结果一 致。     

高矿化度油气田盐卤水对碳钢的腐蚀行为研究

我国高矿化度油气田盐卤水资源丰富,为保障油气田开采和卤水综合利用过程的安全,采用失重法、扫描电镜、能谱分析和交流阻抗测试技术研究了碳钢在高矿化度卤水中的腐蚀行为。研究结果表明：碳钢的平均腐蚀速率随着温度的升高先增大后减小,在70℃时出现峰值,矿化度增大促进平均腐蚀速率升高;卤水中的Na+易于形成NaCl晶体沉积在钢表面,Ca2+有最大的参与成膜倾向,而Mg2+在产物膜中的含量较低;腐蚀产物膜的微观缺陷将导致点蚀源出现,当点蚀坑超过临界尺寸之后会稳定发展,随着时间增长,点蚀的诱发和稳定发展呈现不同的电化学特征,建立了相应的腐蚀等效电路。     

Textual data transformations using natural language processing for risk assessment

Underlying information about failure, including observations made in free text, can be a good source for understanding, analyzing, and extracting meaningful information for determining causation. The unstructured nature of natural language expression demands advanced methodology to identify its underlying features. There is no available solution to utilize unstructured data for risk assessment purposes. Due to the scarcity of relevant data, textual data can be a vital learning source for developing a risk assessment methodology. This work addresses the knowledge gap in extracting relevant features from textual data to develop cause–effect scenarios with minimal manual interpretation. This study applies natural language processing and text-mining techniques to extract features from past accident reports. The extracted features are transformed into parametric form with the help of fuzzy set theory and utilized in Bayesian networks as prior probabilities for risk assessment. An application of the proposed methodology is shown in microbiologically influenced corrosion-related incident reports available from the Pipeline and Hazardous Material Safety Administration database. In addition, the trained named entity recognition (NER) model is verified on eight incidents, showing a promising preliminary result for identifying all relevant features from textual data and demonstrating the robustness and applicability of the NER method. The proposed methodology can be used in domain-specific risk assessment to analyze, predict, and prevent future mishaps, ameliorating overall process safety.     

钢筋阻锈剂在混凝土中的应用

通过不同掺量的钢筋阻锈剂在砂浆中的阳极极化试验,混凝土拌合物的坍落度、坍落度损失、凝结时间、含气量以及混凝土抗压强度试验,抗渗与抗冻融等耐久性试验,盐水浸烘试验,证明在混凝土中掺入FAC-13型钢筋阻锈剂对混凝土的坍落度与坍落度损失、凝结时间、抗压强度以及渗水高度、质量损失、相对动弹模量等耐久性能无明显影响,而氯离子扩散系数、钢筋的锈蚀率及失重率有显著降低,证明该阻锈剂对钢筋阻锈效果明显,在实际工程中应用取得了很好的效果。     

固井水泥环在川东气田地层水中的腐蚀特征

针对川东气井地层水中的固井水泥，采用电化学测试、扫描电镜观察和能谱分析，研究了水泥环腐蚀的电化学、微观结构和元素分布特征。结果表明：浸泡初期，钢的交流阻抗的高频容抗增大，低频出现Warburg阻抗，水泥/套管钢界面由于水化作用而变得更加稳定，钢的电位在26d后负移约200mV，此时腐蚀介质已经到达钢表面，在水泥未被腐蚀解体时，界面遭到破坏，使交流阻抗的高频容抗减小，低频出现容抗弧；腐蚀后水泥表层的Ca、O含量减少，而C、S、Mg的含量增加，水泥环发生了H₂S腐蚀、CO₂腐蚀和Mg腐蚀H₂S腐蚀较严重，外表面呈溶出型腐蚀，而在内部，腐蚀产物滞留其中，腐蚀主要使孔隙和胶结性发生劣化；Cl^-在水泥中具有较强的渗透性。研究成果对含H₂S和CO₂的酸性气田的固井工作具有指导意义。     

高温在线腐蚀监测机构温度场分析

采用ANSYS软件对高温在线腐蚀监测机构进行温度场分析,分析了沿探针杆中心轴线和沿保温层径向的温度分布情况。分析采用比现场更苛刻的数据作为模拟数据。用传热学中精度较高的经验公式来计算管道内外侧的对流传热系数。模拟分析的结果对密封填料、探针、保温层、闸阀、法兰等的设计及选用具有指导作用。分析显示保温层壁温和理论计算结果误差在0.02%以内,所设计和选用的零部件能用于高温管道中。