CAP1400双乏燃料贮存格架地震条件下流固耦合试验研究

CAP1400是中国自主研发的新型反应堆，其乏燃料贮存格架自由地放置在乏燃料水池内，水可在格架内部通道中流通，同时水也存在于格架与格架、格架与池壁之间的间隙中。在地震情况下，格架与流体之间的流固耦合特性非线性度非常高，很难用软件准确地模拟计算。为准确地探究CAP1400乏燃料贮存格架的流固耦合特性，建立了乏燃料贮存格架和水箱缩比试验模型，开展了振动台试验。在扫频试验中，测量了格架支脚与水箱底板间的摩擦系数；同时研究了正弦波、地震波工况下，格架与格架间的间隙对格架滑移现象、流体压力的影响。通过分析试验结果，得到了格架支脚与水池间的摩擦系数；且格架间隙越大，流体压力越小，但格架间隙对滑移现象影响不明显。本试验的结果可为CAP1400乏燃料贮存格架的流固耦合参数选取提供依据。     

乏燃料水池贮存格架水下安装工艺研究

通过拆除乏燃料水池内原有的乏燃料贮存格架,安装更密集的乏燃料贮存格架,可提升乏燃料水池的贮存能力。以国内某商用核电站乏燃料水池扩容改造为研究对象,分析了乏燃料贮存格架在水下安装的难点,提出了根据测量池底的不平整度调平乏燃料贮存格架的垂直度,然后在水下进行定位安装施工,并制定了乏燃料贮存格架水下安装精度检验方法。在水下安装的乏燃料贮存格架达到了使用规定的位置、高度和垂直度,保证了燃料组件的安全装载。该工艺可为国内各大核电站进行乏燃料水池扩容改造提供经验参考。     

新型乏燃料贮存格架自主研制

自主研发一种新型乏燃料贮存格架。基于该乏燃料贮存格架的结构,从临界安全、热工水力和力学抗震等方面论证新型乏燃料贮存格架的安全性、可靠性。为了验证新型乏燃料贮存格架的设计合理性和制造工艺可行性,制造1台工程样机,并进行支腿调节试验和模拟组件插拔试验。通过样机的制造和试验表明,新型乏燃料贮存格架设计合理、制造可行,可以批量化生产。     

核电厂乏燃料贮存格架水下去污装置研制

针对核反应堆乏燃料贮存格架去污的必要性与功能要求，研制了一种二代核电厂乏燃料贮存格架水下冲洗去污装置。详细介绍了该装置的结构组成、功能原理及控制系统设计。经某核电厂现场使用验证，该装置操作简便，具有良好的冲洗去污能力，可大幅降低乏燃料贮存格架的辐射剂量水平。      

海洋核动力平台乏燃料贮存格架设计及安全分析研究

针对海洋核动力平台乏燃料组件海上长期贮存所面临的安全保证问题,通过改进燃料组件与贮存小室之间固定形式、优化贮存小室与贮存格架本体之间连接形式以及增加贮存格架与乏燃料水池池壁之间的缓冲结构,设计了一种满足设计基准以及适应海洋环境的乏燃料贮存格架,并采用蒙特卡罗程序MCNP-5、计算流体力学软件Fluent 14.0、有限元分析软件ANSYS 17.0对该贮存格架进行临界、热工、结构仿真计算。结果表明,该贮存格架设计合理、安全性高,可为海上浮动式核电站乏燃料贮存提供解决方案。      

秦山核电二期工程乏燃料贮存格架的设计

在秦山核电二期工程的设计中，乏燃料的贮存采用了中子毒物镉的密集型贮存格架，与疏松型贮存格架相比，大大提高了乏燃料贮存水池单位面积的贮存能力。镉密集贮存格架的设计在国内尚属首次．本文介绍了该型贮存格架的方案选择以及设计中考虑的主要原则和要求。     

乏燃料贮存格架的试制

简要介绍了乏燃料贮存格架实体模型试制过程中的生产准备、材料要求、关键零部件的加工、组焊、检验以及抽插试验的过程，为乏燃料贮存格架产品的制造和国产化提供了经验。     

乏燃料贮存格架时程分析方法

乏燃料贮存格架是用于贮存换料后的乏燃料组件的重要设备,其自由放置在核电厂乏燃料水池中,在地震载荷下的响应属于非线性响应,包含了各种复杂的运动:滑移、碰撞、扭转、倾覆等。为了准确描述上述非线性响应,本文建立了乏燃料贮存格架整池有限元模型并进行非线性时程分析,考虑了滑移、碰撞、摩擦等影响因素,同时还考虑了乏燃料贮存格架在水池中的流固耦合效应。通过时程分析得到了乏燃料贮存格架在地震载荷下的位移、载荷等计算结果。该方法可用于乏燃料贮存格架的抗震分析。     

乏燃料贮存格架流固耦合参数的数值模拟

乏燃料贮存格架是储存乏燃料组件的重要设备。在地震载荷下，其响应是非线性的，可能产生滑移、颠覆等。发生地震时，存在于格架间隙内的流体耗散了结构的能量，保证了格架的完整性。本文使用3/10缩比模型，利用CFD软件Fluent进行了乏燃料贮存格架2D瞬态分析。计算过程中利用动网格方法模拟格架强迫振动，并进行了参数不确定性分析。利用CFD瞬态流体力分别获得了双Ⅱ区、双Ⅰ区格架附加质量矩阵。利用同轴圆柱体附加质量的计算解与解析解进行对比验证，证明了本文计算方法的准确性。本文计算所得的附加质量矩阵可为乏燃料贮存格架结构动态软件提供流固耦合参数。     

秦山核电二期工程乏燃料贮存格架的抗震分析及结构优化设计的探讨

本文描述了乏燃料贮存格架的结构及独特的抗震设计,介绍 乏燃料贮存格架抗震分析的方法和结论,并针对结构的特殊性,提出了对计算内容的补充,使得分析内容更为科学严谨和完整,通过研究影响贮存格架抗震性能的主要因素,总结了乏燃料贮存格架在抗震设计上的一些参考依据和优化设计观点。     

基于机器视觉技术的乏燃料贮存格架自动定位试验方法研究与应用

The positioning test of spent fuel racks is a key test in the commissioning of nuclear fuel handling and storage system. It directly affects the safety and efficiency of the receiving and storage of nuclear fuel assemblies. In this paper, the traditional manual positioning test method is studied, and an automatic positioning test method based on the machine vision technology is proposed. Engineering application shows that this method can greatly improve the efficiency of positioning test and reduce the need of manpower. Furthermore, it is also effective in the exclusion of foreign material and the protection of finished products. Therefore, it has considerable benefits in economic, safety and quality.     

基于离散动态事件树的风险指引的安全裕度分析方法研究

风险指引的安全裕度是近十年来核工业界提出的新的安全理念。本文阐述了基于离散动态事件树的风险指引的安全裕度分析方法,给出该方法下核燃料包壳失效概率均值和标准差的数学表达式。针对简化压水堆模型下的全厂断电事故,提出了基于离散动态事件树的风险指引的安全裕度计算流程,计算了两种离散动态事件树分支规则下燃料包壳失效的风险指引的安全裕度及其不确定性。计算结果表明,不同的分支规则、模型参数分布、系统程序最大时间步长对核燃料包壳失效概率均值和标准差均有显著影响。提出了一种改进的可变概率阈值的分支方法,以更好地平衡风险指引的安全裕度分析过程中计算精度与计算资源的匹配问题。     

Nuclear safety of spent fuel pool storage at nuclear power plants with VVER-1000: physical principles and structural solutions

The physical principles and structural solutions concerning nuclear safety in handling nuclear fuel at nuclear power plants with VVER-1000 are examined. It is shown that a structure of storage racks in the holding pools based on the spacing of hexahedral boron steel pipes, the structure acting as a combined neutron trap, will increase the pool capacity as compared with the loosely packed pools and will make the handling of nuclear fuel nuclear safe under normal operating conditions and during accidents. In the future, this construction will make it possible to use fuel assemblies with high uranium content and fuel enrichment above 5%.     

美国放射性废物最终处置政策及技术路线

反应堆安全和核废物安全处置被认为是影响今后核能事业发展的两大障碍。自１９８０年以来，美国颁布了３个关于核废物处置的政策法令，对放射性废物的安全处置的要求及责任做出了明确规定。文章介绍了美国放射性废物处置的政策、技术路线及现状。对乏燃料及高放废物的处置，美国采取了比较慎重的态度，进行了各种方案的比较，虽然已有基本轮廓，但仍在探索之中。文章还介绍了高放废物处置中存在的一些有争议的重大问题和倾向性意见。     

压水堆核电厂乏燃料组件源项计算分析

核燃料贮存、运输以及后处理过程中的安全是构成核与辐射安全的重要内容,为保证安全性,提高运输经济性,减小后处理厂对环境的排放,须获得乏燃料组件的包络源项,因此,采用ORIGEN-ARP程序分析组件运行历史、初始富集度、燃耗深度等参数对源项的影响。运行历史在卸料初期对源项略有影响,可采用合适的保守因子予以包络,在冷却一定时间后,其影响可忽略不计;初始富集度、燃耗深度均不同的组件须经对比计算以获得包络源项。计算表明：在目前核电厂乏燃料组件中,²³⁵U初始富集度为4.45%、燃耗深度为55 GW•d/tU的AFA-3G型组件源项是包络的,可作为乏燃料水池、运输容器设计,以及后处理厂排放源项分析的初始源项。     

MOX燃料贮存水池核临界安全分析

利用MONK程序对MOX热室项目燃料贮存水池进行了核临界安全分析。针对给定的水池尺寸和燃料棒数量，确定燃料以分区方式贮存。选取国际公布的临界基准实验数据，验证并确定MONK程序计算分析类似物料形态时的偏倚和次临界限值，其次进行保守假设，确定贮存水池在正常及事故工况下其中子有效增殖因数，评价贮存水池的安全性。计算结果表明，贮存水池在最危险事故工况下，其最大中子增殖因数小于次临界限值，系统处于临界安全状态。     

Seismic isolation of pool-type tanks for the storage of nuclear spent fuel assemblies

Seismic isolation of pool-type nuclear spent fuel storage tanks requires careful investigation of dynamic behavior of the fluid–structure–isolator interaction system to satisfy the requirements of safety functions and the prevention of nuclear criticality. This paper presents the investigation, results and discussions on the seismic design considerations of isolated pool-type tanks for the storage of nuclear spent fuel assemblies. A three-dimensional boundary element-finite element method is presented for the analysis of the fluid–structure–isolator systems in time domain. Scaled model tests were performed to verify the numerical method and to study the dynamic behavior of isolated pool-type storage tanks. Important factors affecting the dynamic behavior of tanks with a fixed base are further investigated as is the case for isolated tanks using base isolators with different mechanical properties. The base isolators are the high damping rubber-bearing type and are modeled using a bilinear analysis model. Based on the numerical analysis and experimental results, some conclusions and discussions on the design considerations for isolated storage tanks are presented. In general, it is shown that careful selection of mechanical properties of the isolators with a certain lower limit on the effective frequency can guarantee the reduction of the dynamic responses of the storage tanks and the enhancement of the stability of stored spent fuel assemblies against earthquake excitations.     

Approach to Safety Assessment of Methods for Handling Liquid Radioactive Wastes from Nuclear Fuel Cycle Enterprises

The application of the concept of deeply layered protection, which was developed for nuclear power plants, to modern methods for handling liquid radioactive wastes is examined. It is shown that this concept can be used successfully for assessing the safety status of different types of storage sites. It is concluded that it is desirable to develop for domestic nuclear fuel cycle objects a multilevel safety concept based on the principle of deeply layered protection and later to prepare on this basis the standardization documentation.     

Meeting EU's energy needs through nuclear fission: Synergy of public and private research in an international context

The availability of an affordable and sustainable energy supply is becoming a major and growing concern for world's future. It is very likely that there is not one single solution to the problem but that it is necessary to call upon a whole set of means such as energy efficiency improvement, deployment of renewable energies, clean coal technologies including CO₂ capture and storage, nuclear development. Indeed, it is more and more recognized that nuclear energy offers a very effective way to contribute to this worldwide challenge. It can be a safe, clean, reliable and cost-effective source of energy, the price of which remaining quite stable. Although the “generations” of nuclear systems are at different degrees of maturity, the scientific, technological and industrial gaps are quite well identified and assessed so that it is possible to describe a detailed roadmap of their development, including R&D needs.A significant part of these R&D needs should be addressed through cooperation involving public and private sector. It is the case for programs relating to safety, radiation protection, PRA (probabilistic risk assessment) methodology, background knowledge about ageing, fuel and fuel cycle for future light water reactors (Gen 3), pre-normative research for the purpose of harmonizing safety demonstration methodologies, Gen 4 systems with an emphasis on sodium-cooled fast breeder, large R&D infrastructures like test reactors and more generally, all obstacles to a consensual development of nuclear energy. R&D program should also be helpful in maintaining appropriate expertise and competencies.Strong cooperation between countries and between stakeholders is necessary to face all these challenges.