Shifting strategies and precarious progress: Nuclear waste management in Canada

Canada has a lengthy history of trying to find a path for dealing with radioactive spent fuel and nuclear waste from its nuclear reactors. In the last decade, it has taken major strides towards this goal by evolving a process through which a site for a geological repository to sequester nuclear waste is to be selected. The Canadian Nuclear Waste Management Organization (NWMO) is in the early stages of the process of finding a community that is willing to host such a repository. Differences between the broad principles underlying siting and the processes for actually selecting the site have emerged as the NWMO proceeds with engaging local governments and specific communities. These differences and other conflicts, especially over new nuclear reactor construction, might pose hurdles in the path of successfully setting up a repository.     

Effects of deep geological environments for nuclear waste disposal on the hydrogen entry into titanium

The surface of nuclear waste container will be completely wetted by the groundwater infiltrating through the bentonite or concrete buffer after the closure of its deep geological disposal. Because of its excellent corrosion resistance, titanium is one of the candidates for the container materials for high-level nuclear waste (HLNW) disposal. However, once oxygen depleted in the large time scale deep geological disposal, titanium container will suffer from hydrogen embrittlement (HE). Therefore, in order to predict the potential danger of the HLNW container caused by HE, the hydrogen entry into titanium was studied at different temperatures in simulated deep geological environment of Beishan, which is the preselected HLNW disposal area in China. Devanathan-Stachurski cell methods were firstly implemented in measuring apparent hydrogen diffusivity in titanium with hydrides being formed during hydrogen charging at low temperature ranges (298–373 K). Given the characteristic of the Devanathan-Stachurski cell method's capable of getting apparent diffusivity with combined influencing factors easily, the technique provides a simple way to measure the parameter that is necessary for the estimation of hydrogen penetration depth, facilitating the design of HLNW containers.     

HEAT TRANSFER ANALYSIS OF NUCLEAR WASTE CASKS STORED IN THE YUCCA MOUNTAIN REPOSITORY

ABSTRACT

A numerical model of the residual heat associated with stored nuclear waste casks proposed for long-term storage in Yucca Mountain has been developed. The Yucca Mountain Repository, located about 100 miles from Las Vegas, NV, is the proposed long-term geologic repository for high-level nuclear waste. STAR-CD, one of several commercial computational fluid dynamics packages being used for the assessment studies, was used to establish the numerical model. The model was developed to simulate the fluid flow and heat transfer within the drift tunnels generated by the waste casks over a 10,000-year time cycle. The model shows that the heat generated from within the casks is partially removed by ventilating air moving through the drifts and conduction through the drift walls. Thermal radiation was found to have little effect on overall cooling compared to the roles of natural convection adjacent to the casks and forced convection from the drift ventilation.     

Analysis of possible geological storage of CO2 and nuclear waste in Lithuania

Lithuania is currently dealing with two major problems in energy sector: final closure of Ignalina Nuclear Power plant (Ignalina NPP) in the end of 2009 and nuclear waste disposal and climate change mitigation issues having in mind replacement of nuclear capacities with fossil one and anticipated increase in GHG emissions. Lithuania has two options: to construct new nuclear power plant also taking into account nuclear waste disposal issue or to burn fossil fuel and to apply carbon capture and storage (CCS) for GHG emission reduction. These two options need to be investigated in Lithuania based on various studies conducted in Lithuania and abroad dealing with geological carbon storage and nuclear waste disposal potentials. There are no long-lived nuclear waste geological storage capacities in Lithuania and there is no pilot project on CCS developed in Lithuania. The aim of the article is to analyse and compare geological carbon and nuclear waste storage opportunities in Lithuania and to assess nuclear and carbon capture and storage technologies in terms of costs.     

Rate controlling reactions for copper corrosion in anaerobic aqueous sulphide solutions

Abstract

The long term corrosion behaviour of copper in anoxic aqueous sulphide solutions has been studied using corrosion potential and electrochemical impedance spectroscopy measurements and scanning electron microscopy on corroded surfaces and cross-sections of surfaces prepared using a focused ion beam. Experiments were conducted in solutions containing either 5×10^?4 or 5×10^?5 mol L^?1 sulphide for 1691 and 4000 h respectively. In the more concentrated solution, a coherent, compact and crystalline chalcocite (Cu₂S) film accumulated on the corroding copper surface. A parabolic growth law was obtained, and the kinetics were controlled by Cu(I) ion transport either through the Cu₂S matrix or along crystalline grain boundaries in the film. In the more dilute solution, the growth of a less crystalline, porous chalcocite layer followed approximately the linear growth kinetics controlled by sulphide ion transport through the pores. If the sulphide was allowed to deplete in the dilute solution, rate control switched to sulphide diffusion in the bulk solution. The implications for waste container corrosion in a nuclear waste repository are discussed.     

Comparison of carbon dioxide and nuclear waste storage costs in Lithuania

Nuclear power and carbon capture and storage (CCS) are key greenhouse gas mitigation options under consideration across the world. Both technologies imply long-term waste management challenge. Geological storage of carbon dioxide (CO₂) and nuclear waste has much in common, and valuable lessons can be learnt from a comparison. Seeking to compare these technologies economic, social and environmental criteria need to be selected and expressed in terms of indicators. Very important issue is costs and economics of geological storage of carbon dioxide and nuclear waste. The costs of storage are one of the main indicators for assessment of technologies in terms of economic criteria.The paper defines the costs of the geological storage of CO₂ and nuclear waste in Lithuania, drawing also on insights from other parts of the world. The costs of carbon dioxide and nuclear waste storage are evaluated in UScnt/kWh and compared. The paper critically compares the characteristics and location of the both sources of and storage options for CO₂ and nuclear waste in Lithuania. It discusses the main costs categories for carbon dioxide and nuclear waste storage. The full range of potential geological storage options is considered and the most reliable options for carbon dioxide and nuclear waste are selected for the comparative costs assessment.     

State of the art of geothermal reservoir simulation

Computer modeling of geothermal systems has become a mature technology with application to more than 100 fields world-wide. Large complex three-dimensional models having computational meshes with more than 4000 blocks are now used routinely. Researchers continue to carry out fundamental research on modeling techniques and physical processes in geothermal systems. The new advances are adopted quickly by the geothermal industry and have also found application in related areas such as nuclear waste storage, environmental remediation and studies of the vadose (unsaturated) zone. The current state-of-practice, recent advances and emerging trends in geothermal reservoir simulation are reviewed.     

滑带控制型边坡地震稳定性分析

针对滑带控制型边坡动力稳定性问题,提出了一种基于滑带局部强度折减下的完全动力有限元分析方法,根据地勘资料在基岩和滑体间建立薄层单元模拟滑带,以滑带最后塑性屈服附近点作为整体安全系数关注点,以可能形成滑动通道的局部贯通点作为局部安全系数关注点,采用粘弹性人工动力边界,在静力折减应力场的基础上进行同等程度下的动力折减,根据关注点动力位移拐点进行动力失稳判断。实例应用结果表明,该方法合理、有效。     

我国核电及核能产业发展前景

从减排、能源结构调整、环境保护角度分析核电在我国能源结构和我国科技体系中的定位及核电发展的必要性,根据我国运行核电厂的实际情况和自主设计的先进核电厂特性说明核电的安全性,同时根据运行核电厂放射性排放数据论述核电厂对环境和公众不造成任何有害的影响,并对核燃料循环、核废物对策和处理措施进行了论述。预测核电中长期发展情景,通过评估核电及配套核燃料产业能力,以及装备及相关行业发展情况,表明我国工业基础能够支撑核电的规模化发展;并反过来,核电将促进相关行业大发展,提高其技术水平,高科技含量,发展成高端产业,有利于我国经济转型。     

Code development for analyzing transient behaviors induced by the in-box LOCA of liquid blanket in hydrogen fusion energy systems

Blanket is the strategic component in hydrogen fusion energy system, converting nuclear energy of hydrogen nuclei to thermal energy which could be further transported for the production of electricity. In order to investigate blanket transient behaviors induced by the in-box LOCA (Loss of Coolant Accident), a code named LBBFoam for high pressure compressible multi-phase flow is developed based on OpenFOAM, which is capable of simulating accident-induced pressure wave propagation in the blanket module. Two classic one dimension shock tube cases were simulated to verify the code. With this code, three scenarios with 8 MPa helium injection into PbLi in a blanket-like container were analyzed to capture pressure oscillation and bubble transportation characteristics. It is found that the maximum pressure in the PbLi zone exceeds and even doubles the helium injection pressure due to the reflection and superposition of pressure waves. This suggests that the traditional structural safety design limits of helium cooled PbLi blanket, which is usually set as the operating pressure of helium coolant, would be too low considering pressure wave superposition. This code will provide an assessment tool for the structural safety of blanket.     

Three-dimensional thermal analysis of the repository for high-level radioactive nuclear waste

One of the key issues of the dimensioning design and safety assessment of the repository for deposing the high-level radioactive nuclear waste is the temperature distribution. A three-dimensional layered model was established for analyzing the heat conduction near single waste canister. Applying the Laplace transform and finite Fourier Sine transform upon the governing equations of heat conduction, the solutions in the Laplace domain were obtained. The solutions in the Laplace domain were numerically inverted into semi-analytical solutions in the time domain by the Crump method, and the temperature distribution was obtained near the canister at the center of one disposal panel. The initially estimated value of the canister spacing was determined according to the temperature distribution and design criterion. Finally, the obtained temperature distribution was used to investigate the influence of relevant parameters on the canister surface temperature. The results show that the present model is reliable by comparing with the existing analytical model. The peak canister surface temperature is significantly affected by the tunnel spacing, canister spacing, thickness of buffer layer, and thermal conductivities of buffer material and surrounding rock.     

基于人工神经网络的长周期储存式压力容器安全评价研究

本文基于人工神经网络，设计了一个长周期储存式压力容器安全分析评价系统。按压力容器自身的特点进行建模，选择三种类型缺陷为模拟对象，利用有限元应力分析进行应力计算，获取各种状态的应力数据作为训练的样本故据，并选用带二次动量项的BP算法对样本数据进行学习，进而建立长周期压力容器安全评价智能系统软件，最后将该评价智能系统软件计算的结果与GB／T19624—2004《在用含缺陷压力容器安全评定》计算结果走行比对，系统准确性高。利用该软件使压力容器安全评价变得方便、快捷、简单。     

Finessing the fuel: Revisiting the challenge of radioactive waste disposal

It is pointed out that the apparent decision of the United States to end development of the Yucca Flat, Nevada repository for permanent disposal of radioactive waste may inadvertently place it at variance with the disposal principles of the International Atomic Energy Agency (IAEA) which caution nuclear nations that “The burden on future generations shall be minimized by safely disposing of high level radioactive wastes at an appropriate time, technical, social and economic factors being taken into account.” It is then shown that the IAEA's ten technical criteria for underground disposal can seemingly be met by storing vitrified waste a kilometer underground in the crystalline basement rock of a mid-continent shield, where: (a) it should be invulnerable to redistribution by incompetence, natural disaster, or terrorism and (b) there is no obvious pathway for leakage into the biosphere. Finally, a method is proposed by which the storage impasse may be broken.     

两河口水电站泄洪出口边坡渗流及稳定性计算分析

在分析两河口水电站泄洪洞出水口边坡工程地质条件的基础上,研究了边坡岩体的渗透特性,结合雾化降雨试验资料、采用饱和非饱和渗流有限元方法计算并分析了边坡雾化雨条件下渗流场的变化规律,同时引用非饱和强度理论并运用Sarma极限平衡方法分析了雾化雨对边坡稳定性的影响,所获得结论可为正确评价边坡岩体的稳定性、合理可行的工程控渗及边坡加固措施提供依据。     

某水电站雾化区边坡降雨入渗及稳定性分析

基于某水电站右岸高边坡基本地质条件和雾化雨资料,采用饱和-非饱和渗流有限元分析方法,研究了边坡在雾化雨条件下的渗流场变化规律,并借鉴非饱和强度理论,运用强度折减法分析了雾化雨对边坡稳定性的影响。分析结果表明,雾化雨条件下地表水入渗将导致非饱和区范围缩小、压力水头升高并出现局部暂态饱和区;考虑非饱和区强度变化及饱和区渗透力影响,降雨入渗时边坡稳定性将明显下降。     

高压注浆法在提高地基剪切波速中的应用

《核电厂抗震设计规范》要求核电厂核安全抗震物项宜坐落在基岩或剪切波速大于400 m/s的地基上,当地基剪切波速小于400 m/s时,需要对其进行换填素混凝土或者加固处理,以满足设计要求。文中通过对台山核电废液储存罐厂房地基处理方案的介绍,从经济和技术两个方面对比分析了开挖换填素混凝土和高压注浆法的优缺点。通过现场实践证明,对于深厚回填土,砂石含量较高时,采用高压注浆法可以将地基的剪切波速提高至400 m/s以上,避免了换填素混凝土时边坡的开挖和支护,施工安全风险小,造价相对较低。高压注浆法特别适用于以提高地基剪切波速为主要目的的深厚回填土的处理。     

逆流形式下废液与空气热湿传递驱动力的解耦分析及实验验证

为了深入研究逆流形式下废液与非饱和空气热湿传递过程中传热驱动力与传质驱动力之间的关系,建立了逆流形式下废水和非饱和空气的热质交换耦合模型,利用数学方法对该模型的热湿传递驱动力进行解耦分析。将利用根据文献中逆流除湿/再生搭建的实验装置和本文搭建的废液再生实验装置得到的实验数据进行比较、验证。结果发现:相互耦合的温度差驱动力Δt和含湿量差驱动力Δω可以由相互独立的焓差驱动力Δh和相对湿度差驱动力Δφ表示,这两个相互独立的驱动力可以用来独立表征废液和非饱和空气的传热传质过程;相关文献中的和该装置中的实验结果与解耦分析的数值模拟结果一致:非饱和空气出口的所有参数在相互独立的驱动力所界定的范围内变化。     

作业面过断层破碎带加固技术

断层作为煤矿井下生产中十分常见的一种地质构造形式,确保回采作业面通过断层时的安全、高效,对于提升矿井生产综合效益意义重大。以此为着手点,针对作业面过断层破碎带加固技术开展探究,结合具体工程实际,在运用数值模拟手段开展过断层模拟分析的基础上,对过断层破碎带加固技术做出具体分析,并对其应用效果进行监测。结果表明,所设计的方法确保了作业面过断层期间的围岩稳定性,确保了回采安全。     

考虑非饱和区的复合土工膜防渗坝渗流分析

针对传统的渗流分析主要考虑饱和区的渗流而不考虑非饱和区的渗流存在一定的安全隐患问题,基于饱和—非饱和渗流理论,结合复合土工膜防渗坝设计了四种不同的水位组合,分别计算了饱和渗流量及饱和—非饱和渗流量,并分析了正常蓄水位下考虑与不考虑非饱和区的渗流速度场等变化规律。结果表明,考虑非饱和区后单宽渗流量有了明显下降,出溢点的渗流溢出坡降变小,且渗流路径变的较为陡直,靠近上游部分区域的渗透坡降相对较大,水压力在土工膜中的降低相对减小。     

Simulation of thermal state of containers with spent nuclear fuel: multistage approach

The safe thermal conditions of spent nuclear fuel storage are the important component of complex safety of the dry spent nuclear fuel storage facility. The multistage approach for numerical definition of thermal fields in storage containers with spent fuel assemblies is proposed. The approach is based on solving of the series of the conjugate heat transfer problems with different geometrical detailing. The developed approach is used for estimation of thermal state of ventilated containers with spent nuclear fuel of WWER‐1000 reactors of Zaporizhska nuclear power plant. The results of the thermal calculations for single‐placed container on open‐site storage platform were presented. The safety of containers usage in normal and extreme ambient temperatures was proven. Copyright © 2015 John Wiley & Sons, Ltd.