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Shinzo Ueta Hisao Satoh Hiroyasu Kato Akira Ueda Katsuo Tsukamoto 《Journal of Nuclear Science and Technology》2013,50(7):731-741
The effect of alkaline pH on the dissolution rate of bulky aggregated montmorillonite samples at 23 °C was investigated for the first time by using an enhanced phase-shift interferometry technique combined with an internal refraction interferometry method developed for this study. This technique was applied to provide a molecular resolution during the optical observation of the dissolution phenomena in real time and in situ while remaining noninvasive. A theoretical normal resolution limit of this technique was 0.78 nm in water for opaque material, but was limited to 6.6 nm for montmorillonite due to the transparency of the montmorillonite crystal. Normal dissolution velocities as low as 1 × 10?4 to 1 × 10?3 nm/s were obtained directly by using the measured temporal change in height of montmorillonite samples set in a reaction cell. The molar dissolution fluxes of montmorillonite obtained in this study gave considerably faster dissolution rates in comparison to those obtained in previous investigations by solution analysis methods. The pH dependence of montmorillonite dissolution rate determined in this study was qualitatively in good agreement with those reported in the previous investigations. The dissolution rates to be used in safety assessments of geological repositories for radioactive wastes should be obtained for bulky samples. This goal has been difficult to achieve using conventional powder experiment technique and solution analysis method, but has been shown to be feasible using the enhanced phase-shift interferometry. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(5):605-609
Japan's concept for high-level radioactive waste disposal includes a barrier of compacted bentonite (montmorillonite) that, based on its microstructure, buffers the waster package and prevents migration of colloids with sizes between 1 and 1,000 nm. However, results of experimental studies indicate that colloid migration through the barrier (breakthrough) depends upon the partial density of the montmorillonite buffer. To assess the possibility of colloid breakthrough, interstitial pore size as a function of montmorillonite partial density is estimated through a homogenization analysis. Homogenization analysis indicates that interstitial pores sizes of <1 nm may be achieved for montmorillonite partial densities in excess of 1.2Mg/m3. It should be noted that this estimation depends upon the specific structural/geometric parameters of the compacted bentonite under consideration. 相似文献
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Geological disposal has been adopted as the most feasible option for the method of long-term management of high-level radioactive waste (HLW) in every country in the world, regardless of the pros and cons of the nuclear power generation. Building stakeholders’ confidence in safety of geological disposal is indispensable to reach the point where the implementation of geological disposal is accepted by the current generation. The safety case is a key input to build confidence in geological disposal stepwise as the program progresses and regarded to play an important role as a common platform in the communication among stakeholders. The aim of this paper is to review arguments relevant to building technical and social confidence in the progress of Japanese research and development activities as well as international discussions. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(4):441-448
Accelerated short-term leach tests in a laboratory are neccessary in order to estimate, with reasonable accuracy, the long-term leaching behavior of high-level waste glass. In the present study, static leach tests of an SRL-165 high-level waste glass were carried out in deionized water at two different glass-surface-area to solution-volume ratios (SA/V-ratio), namely 0.85 and 0.079 cm?1 at 90°C, and 0.85 cm?1 at 40°C. First, an equation was examined which related Si-concentrations with time, temperature and SA/V-ratio under the present static conditions. The parameter determined at 90°C, 0.85 cm?1 can be used to calculate the Si-concentration at 40°C, 0.85 cm?1. Second, at the low SA/V- ratio of 0.079 cm?1, the concentrations of Ca and Mg in the leachates peaked and then decreased a little. The equation used above does not explain the variation of the concentrations of Ca and Mg at a low SA/V-ratio. The precipitation of Ca and Mg onto the glass surface is probably caused by the adsorption efficiency of the surface layer or the formation of crystalline materials at the low SA/V-ratio of 0.079 cm?1. Third, the in-depth profiles of some elements obtained by secondary ion mass spectroscopy (SIMS) were qualitatively in agreement with the results of solution analyses. This indicates the particular usefulness of SIMS for analyzing leaching behavior of the glass in in-situ burial studies where solution analyses are often impractical. 相似文献
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结合2005年放射性废物处置安全国际大会反映出来的放射性废物处置安全领域的最新进展,介绍了全球放射性废物安全框架、废物处置安全战略、安全方案、地质处置设施安全、近地表处置设施安全、中等深度废物处置方案和公众沟通等方面的若干新进展和新观点。 相似文献
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U、Np、Pu、~(99)Tc、~(79)Se等放射性元素或核素对氧化还原条件敏感,存在多种价态,且锕系元素(U、Np、Pu)具有丰富的配位化学,其在生物圈和地质圈中的化学行为较为复杂。电势(Eh)-pH图对解决在水溶液中发生的一系列反应及平衡问题具有广泛的应用。本工作采用PhreePlot软件绘制了这些元素或核素在人体血清、唾液、胃液、DMEM培养基和北山地下水中的Eh-pH图以研究它们的主要氧化态和赋存形态。结果表明,U在生物圈中的主要氧化态是Ⅵ,Np是Ⅳ,Pu是Ⅳ和Ⅲ,99 Tc是Ⅶ和Ⅳ,79Se是0和Ⅳ。相比其他元素或核素,pH对铀的赋存形态影响更大。在地质圈中,根据Eh-pH图来看,北山处置库有利于Np、Pu的长期储存而对于U、99 Tc、79Se的储存不利。本工作的对比研究也表明,在热力学数据库一致的情况下,采用免费软件PhreePlot绘制的元素Eh-pH图与Geochemist’s Workbench(GWB)程序绘制的Eh-pH图具有高度的一致性。 相似文献
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高放废物处置库选址和场址评价工作过程中会产生海量的数据资源,其具有涉及学科类型多、跨越时间尺度长等特点,因此采用信息技术建立处置库预选区地学信息数据库是非常必要的。本文通过收集高放废物处置库预选区地学领域的多源、多学科数据,并设计和建设多源地学信息数据库,开发实现了高放废物处置库预选区地学信息管理系统。该系统可以实现对地学信息数据库中所有信息数据类型的增删改查等基本操作,也可以实现网页终端的全文检索及下载需求,甚至可以实现对某类专业数据的统计分析。 相似文献
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以往放射性废物处置的安全评价中通常使用放射性安全指标(即剂量和危险),随着放射性废物处置安全全过程系统分析这一概念的提出,辅助指标已成为评价中的一个重要组成部分。本文介绍了安全全过程系统分析中所使用指标的发展、分类和相应标准等。依评价对象不同,辅助指标通常分为安全指标和性能指标,有些组织还提出了安全功能指标;与上述指标相对应的用于比较的标准分别为参考值、指标标准和安全功能指标标准。将处置系统划分为不同库室时,指标还可分为“包容物和浓度”相关指标、“通量”相关指标和“屏障状态”相关指标三类。建议我国尽快开展放射性废物处置的安全全过程系统分析工作,建立完善的指标体系,选取适当的评价指标,并基于我国放射性废物处置的场址特性确定相应的标准,以期实现安全和防护的最优化。 相似文献
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使用PHREEQC软件及OECD/NEA出版的镅热力学数据,利用相关矿物的沉淀饱和指数,计算了镅在北山地下水中的赋存形态,探讨了pH值、方解石、CO2分压及腐殖酸对镅的形态分布与溶解度的影响。结果表明,在近中性条件下镅主要以AmCO+ 3和 AmSiO(OH)2+3形式存在,在碱性条件下易形成AmOHCO3·0.5H2O(cr)和Am(OH)3(cr)沉淀,因此偏碱性的北山地下水有利于阻滞镅的迁移。 围岩中存在的方解石对镅的溶解度和迁移性影响较复杂,在pH 6~8条件下,方解石能微弱地降低镅的溶解度;在pH 8~9.7时,方解石会提高Am(CO3)-2离子的浓度,进而提高镅的溶解度,增强其可迁移性;而在pH 9.7~11时,方解石有利于AmOHCO3·0.5H2O(cr)沉淀形成,从而降低镅的溶解度。当固定pH为7.56时,镅的溶解度随二氧化碳分压升高先降低而后增大,在10-2.25 bar时达最低值。由于易与腐殖酸形成络合物,在弱酸性至弱碱性条件下腐殖酸能提升镅的溶解度,从而增强其可迁移性,应引起重视。 相似文献
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采用穿透扩散法研究了Sr、I和Pu等3种元素在花岗岩中的扩散行为,获得了26℃下离子强度为0.1mol/L的中性水溶液环境中Sr、I和Pu的有效扩散系数分别为(1.24±0.03)×10-13、(2.88±0.02)×10-13、(1.33±0.52)×10-13 m2/s。研究表明,水溶液与花岗岩平衡过程中核素的存在形态与化学种态的变化对其迁移行为有明显影响。 相似文献
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高放废物深地质处置过程中,放射性核素衰变可能产生大量的热量,释放到处置硐室周围环境中将影响深部地质环境局部的水岩作用。为探究温度对新场场址深部地下水化学环境的影响,使用新场场址原状地下水与BS34钻孔深部花岗岩岩样,开展了不同温度下室内水岩作用研究。结果表明:BS34钻孔岩样与原状地下水反应后,水相的pH为6.4~8.5,总溶解固体(TDS)为1653.9~1759.6 mg/L。随着温度的升高,水溶液Na^(+)、K^(+)浓度增大,其中Na^(+)可能来源于钠长石溶解、阳离子交换作用,K^(+)可能来源于钾长石溶解;Ca^(2+)、Mg^(2+)、HCO_(3)^(-)浓度减少,主要以方解石和白云石的形式沉淀析出,反应温度越高,沉淀析出越多。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(3):463-469
Full-scale tests were performed to evaluate the technical feasibility of a transport system with air-bearings at the underground HLW disposal tunnel for pre-assembled heavy disposal packages, which consist of a waste package and buffer material. Transport conditions in the disposal tunnel, such as roughness and unevenness of the curved surface, make it difficult to achieve smooth movement using the commercial airbearing transport system. In order to evaluate the applicability of the air-bearing transport system to such conditions, tests using a full-scale test device (modified package) and simulated tunnel surface were conducted. Based on the tests, the applicability of this transport system to a disposal tunnel was confirmed. 相似文献
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21世纪近20年,我国高放废物深地质处置进入了一稳步发展的新阶段,在法律法规、技术标准、战略规划、选址和场址评价、工程屏障研究、处置库和地下实验室概念设计、核素迁移和安全评价研究等方面取得了显著进展。其主要亮点包括颁布了《中华人民共和国放射性污染防治法》和《中华人民共和国核安全法》,制定了《高放废物地质处置研究开发规划指南》,颁布了《高放废物地质处置设施选址》核安全导则,确定了2020年前开工建设地下实验室、2050年建成高放废物处置库的目标,甘肃北山预选区被确定为我国高放废物地质处置库首选预选区,建立了场址评价方法技术体系,确定了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,建立了我国首台缓冲回填材料热 水-力-化学耦合条件下特性研究大型实验台架(China-Mock-Up),获得了一批关键放射性核素的迁移行为数据,开展了初步的安全评价,完成了地下实验室安全技术研究。确定甘肃北山的新场为我国高放废物地质处置地下实验室的场址。2019年5月6日,国家国防科工局批复中国北山高放废物地质处置地下实验室工程建设立项建议书,标志着我国高放废物地质处置正式进入地下实验室阶段。这一系列工作进展和取得的成绩为我国2020年开工建设地下实验室、掌握高放废物地质处置技术奠定了坚实的基础。 相似文献
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为研究高放废物地质处置库近场裂隙水流-传热-处置室间距的相互作用机理,采用3DEC软件计算裂隙水流-传热-处置室间距相互作用对处置库近场温度分布影响。结果表明:(1)在处置室间距相同条件下,流动的裂隙水显著改变了处置库近场温度场,使岩体温度降低,缩短模型达到稳态所需要的时间。(2)处置室间距增大,温度叠加效应减弱,处置库近场温度越低,并且废物罐表面膨润土温度越低,裂隙出水口水温越低,模型达到稳态所需要的时间越短。(3)水平和垂直裂隙水流共同传热使处置库近场裂隙水流下游区域温度显著高于裂隙水流上游区域。(4)处置室间距为6 m和8 m时,水平裂隙出水口水温高于垂直裂隙,处置室间距为10 m时,水平裂隙出水口水温低于垂直裂隙。 相似文献
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Hidenori Tsuda Colin Walker Fumiaki Shinkai Hirokazu Kishi Mikazu Yui 《Journal of Nuclear Science and Technology》2013,50(11):1110-1113
Japan Atomic Energy Agency (JAEA) has developed a grout database (GDB) comprising the latest technical data of grout materials relevant to the geological disposal of high-level radioactive waste (HLW). Currently, only newly developed grout materials of low pH cements, superfine spherical silica and colloidal silica, which are expected to provide a target pH ≤ 11 leachate, are included in the GDB. Case examples from on-site works and laboratory-based tests that have been published in the literature have been used to add construction and material details to the GDB. The GDB is available online (https://groutdb.jaea.go.jp/grout/ [in Japanese]) for registered users to obtain and provide data of grout technology. Furthermore, the GDB can be used to correlate requirements of mechanical, physical, and/or chemical properties of a grout material to specifically address concerns over safety assessment, material and injection method development, and/or prediction of grout penetration. 相似文献