A Methodology for Simulating Radionuclide Diffusion in Unsaturated Soils

In this paper, a methodology that can be employed to simulate radionuclide migration through unsaturated soils, under laboratory conditions, has been developed and reported. This was achieved with the help of a specially designed half-cell setup to study diffusion characteristics of inactive forms of Cs⁺, Sr⁺² and Co⁺² in two different types of soils, corresponding to their different compaction states. It has been noted that the apparent diffusion coefficient strongly depends on the volumetric water content of the soil. However, increase of the apparent diffusion coefficient for higher volumetric water contents is found to be much less as compared to the lower volumetric water contents.     

高放废物深地质处置：回顾与展望

文章对我国高放废物地质处置研究的历史进行了回顾,并对未来发展进行了展望。我国的高放废物深地质处置研究开发从1985年开始,迄今为止可初步分为3个阶段：①起步和跟踪研究阶段（1985～1998）;②逐步发展阶段（1999～2005）;③政府规划指导阶段（2006至今）。20多年来,我国在国家法律法规、战略规划、选址、工程屏障、核素迁移研究等方面取得了显著进展。我国已经提出在2020年前建成地下实验室、21世纪中叶建成高放废物处置库的目标。研究开发和处置库工程建设分成3个阶段：试验室研究开发和处置库选址阶段（2006～2020）;地下现场试验阶段（2021-2040）和处置库建设阶段（2041～本世纪中叶）。经过全国筛选对比,已初步选定甘肃北山地区为重点预选区,系统的场址评价工作正在进行。已确定采用膨润土作为处置库的回填材料,并初步确定内蒙古高庙子膨润土为我国高放废物处置库的首选缓冲回填材料。工程设计、核素迁移研究和安全评价也取得了一定进展。1999年起与国际原子能机构开展了3期高放废物地质处置技术合作项目,对提高我国的技术水平起到了积极作用。20多年的研究开发工作为我国在21世纪完成高放废物地质处置任务奠定了基础。     

提高斜拉索索力估算精度的方法

振动法是测量实际索力的首选方法,但其测试精度会受到外界环境因素如温度、风和桥面对拉索作用等的影响。本文围绕如何将外界环境因素的影响降至最小,从测量时机的选取、数据处理方法的选择等方面,综合运用随机振动、风工程、非线性和误差分析理论,提出了提高拉索索力估算精度的实用改进方法,得出了一些有意义的结论。并通过哈尔滨松花江斜拉桥实例进行验证对比,结果表明,该方法具有较高的精度。     

核废料地下处置过程中相关动力学问题及控制措施

深地层地下处置是目前首选的核废料处置方案。由于放射性核素的长期的衰变和辐射导致的某些不可预见性因素．综合评估和预测核废料处置场的安全性是至关重要的。本文从理论上分析了核废料地下处置过程中温度场、应力场、渗流场三场相互影响、相互作用的力学机理,并提出了核废料泄漏的防治措施,为核废料地下处置过程中环境评价提供了基础理论依据。     

基岩裂隙水中90Sr迁移的数值模拟

针对我国西北某放射性废物处置场的水文地质情况,通过渗透张量系数计算和溶质迁移参数测试,建立了基岩裂隙水渗透模型和90Sr在基岩裂隙水中的迁移模型.根据以上两个模型的耦合,采用有限差分法,利用MODFLOW软件对90Sr进入处置场地下水后的迁移情况进行了数值模拟预测.计算结果表明,由于机械弥散、对流作用、地质介质的吸附阻滞作用以及核素本身的衰变作用,处置库运行100a后因破坏而导致核素90Sr进入地下水后的有害污染面积比较小,不会对水井及下游造成不利的影响.     

Geotechnical sealing material for coastal disposal facility for soils and wastes contaminated by radioactive cesium

Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0?×?10^?10?m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay–bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0?×?10^?10?m/s was achieved when the effective consolidation stress is equal to or more than 27?kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.     

Horizontal trench system effects on leachate recirculation in bioreactor landfills

Horizontal trenches (HTs) are constructed during the waste filling for leachate recirculation in bioreactor landfills. Leachate distribution depends on HT configuration (i.e., spacing between successive HTs), leachate injection rate, modes of injection, and hydraulic properties and MSW heterogeneity. Presently, the effects of these variables on the moisture distribution have not been studied systematically. This study provides a systematic evaluation of the effect of the HTs variables on the moisture distribution and pore fluid pressures. A two-phase flow model is used to model a bioreactor landfill having an HT leachate injection system. It quantifies the effects of the unsaturated hydraulic properties and MSW heterogeneity, trench configuration, leachate injection flux, and mode of injection on hydraulic behaviour. The results show that unsaturated hydraulic conductivity and MSW heterogeneity significantly shape the zone of influence and excess pore pressures. Under heterogeneous-anisotropic conditions, the leachate migrates more laterally and the developed pore-pressures are lower than for homogeneous MSW. A closely-spaced, multi-level, staggered HT system is found to provide uniform and adequate moisture distribution in MSW. An intermittent mode of injection that alternates between the shallow and deep trenches with a higher leachate injection flow rate is found to be effective to control the excess pore pressures.     

三元复合驱采出污水回注渗透率的影响因素分析

基于大庆油田三元复合驱采出污水回注对地层存在的损害现象,研究了污水回注渗透率的影响因素。采用室内水驱实验方法,对三元复合驱采出污水中悬浮物、油、碱、聚合物等因素进行了分析,阐述了各种成分对渗透率的影响机理。结果表明,悬浮物颗粒会堵塞孔隙喉道,油产生的"贾敏效应"将增大油水流动阻力,碱与岩石及黏土矿物间的物理化学作用会使地层结垢,聚合物在岩芯中的吸附和滞留共同造成地层渗透率的下降。因此,建议将三元复合驱采出污水中悬浮物、油、碱、聚合物等处理合格后再进行回注,以减轻对地层的损害。     

填砂裂隙岩体渗流传热模型试验与数值模拟

选取中国高放射核废物地下处置库重要预选场区--甘肃北山地区的花岗岩,加工组合成规则裂隙岩体,将垂直裂隙用粒径为0.5～0.63 mm的砂土填充,进行了裂隙水渗流传热试验;对模型试验进行了数值模拟,进而计算分析了热源温度、裂隙水流速和裂隙开度变化对裂隙岩体模型稳态温度场的影响。模型试验表明,当热源温度维持在120 ℃时,裂隙水仍无相变,裂隙岩体模型稳态温度场分布规律与热源温度为95 ℃时一致;热源温度越高,热源的水平影响距离越大,模型达到稳态需要的时间越长;裂隙填砂加强了裂隙两侧岩石之间的热传导,热源的水平影响距离和模型到达稳态需要的时间均明显大于无填充裂隙岩体模型的情况。模型试验得到的岩体模型温度场与数值计算得到的岩体模型温度场规律一致。试验过程中裂隙岩体模型在边界上存在一些热量散失,无法与数值计算中的绝热边界条件等同,致使试验数据低于数值计算值,并且热源温度越高,两者之间的差异越大。模型试验和数值计算均表明,邻近热源侧的裂隙水渗流对模型的温度场分布起控制作用,而远离热源侧的裂隙水渗流则主要影响该侧的边界温度和模型达到稳态所需要的时间。数值参数敏感性分析表明,裂隙水流速与裂隙开度越大,裂隙水对水平传热的阻滞作用越明显。     

城市生活垃圾填埋场沉降监测与分析

2006年9月起于上海老港填埋场开展了示范工程沉降监测项目。该生活垃圾填埋场占地面积约为200 m×125 m,共填埋了约15×104 t来自上海城区的生活垃圾,最大填埋厚度约为9 m。通过填埋期间埋设的水平沉降管,监测到该填埋场不同埋深处的沉降值。介绍了沉降监测系统的工作原理,分析了2006年底至2008年底为期两年的沉降数据。填埋场底部沉降管监测数据表明,场底地基沉降较小,两年的平均沉降为 ～ cm;中部沉降管监测数据表明,该沉降管下方生活垃圾在上方垃圾填埋后产生了较大的压缩,从上方垃圾开始填埋至填埋完毕3个月内的压缩应变约为0.197～0.242;顶部沉降管和中部沉降管监测数据表明,该填埋场垃圾主压缩完成时间约为3个月;由于填埋垃圾有机物含量较高,其修正次压缩指数较大,约为0.066～0.070。