Lifetime and ageing management of nuclear power plants: A brief overview of some light water reactor component ageing degradation problems and ways of mitigation

The susceptibility and tendency for nuclear power plant (NPP) components to undergo changes in their mechanical and physical properties in the course of the NPP lifetime is generally termed as “ageing”. The light water reactor (LWR) nuclear environment is not a begnign one; it is characterized not only by fast neutrons, which can degrade metallic structures, but also relatively high temperatures of coolant water (around 300°C) which may contain impurities (e.g. sulphate, chloride, peroxides) which can cause corrosion. The hydrodynamical conditions of the coolant in steam generators, for example, can cause thermal fatigue, erosion and corrosion; suspended particulate matter can accelerate erosion processes which can lead to wall thinning and lowering of safety margins. Ageing is, therefore, a very complex mixture of factors concerned with materials, temperatures, times of exposure to environments which vary with time and with respect to chemical composition and flow charactertistics.

The paper describes a few ageing phenomena which can be considered important due to their impact on nuclear safety issues; their influence on economic aspects (availability) of NPP is outlined. Mitigation measures for NPP component ageing problems are given together with recommendations for addressing such issues in NPP now and in the future.     

Rapid synthesis of La0.7Sr0.3MnO3+λ catalysts by microwave irradiation process

Microwave irradiation processing (MIP) was considered as a potential method to synthesize perovskite-type oxides rapidly, cleanly and energy-efficiently. In this paper, La_0.7Sr_0.3MnO_3+λ, a kind of promising catalyst for automobile exhaust purification, was successfully prepared by MIP in not more than 5 min. The sol–gel method was also used for comparison. All the samples were evaluated by catalytic activity tests in the simulated exhaust and characterized by XRD, BET, TEM and XRF analyses. The results showed that the integrated perovskite-type phase and uniform particle size were obtained in the microwave-treated samples. And those ones exhibited a better oxidation activity under slightly oxygen-rich condition than that by sol–gel method, which may be related to more A-site cation vacancies and larger bulk oxygen content generated in MIP. Possible formation mechanism of perovskites in MIP was also discussed.     

Coupling of reaction and separation at the microscopic level: esterification processes in a H-ZSM-5 membrane reactor

A catalytically active zeolite membrane has been used to displace equilibrium by selective water permeation during ethanol esterification. Unlike previous works in which water separation was carried out by zeolitic membranes that did not take part in the reaction, the H-ZSM-5 membrane used in this work had sufficient catalytic activity to carry out the esterification of ethanol with acetic acid, and at the same time was selective for water permeation. As a consequence, the reaction and separation functions could be coupled very efficiently, and the conversion obtained at the same feed rate and catalyst loading was greater than in conventional fixed bed reactors, or in reactors where the zeolite membrane was kept separated from the catalyst.     

Synthesis, characterization and catalytic application for wet oxidation of phenol of iron-containing clays

High-surface-area pillared clays (PILC) were prepared from naturally occurring montmorillonites by exchanging interlayer ions to polyoxocations containing (i) aluminum (Al₁₃-PILC), (ii) iron adsorpted onto Al₁₃-PILC, and (iii) iron and aluminum located within the same complex (Fe_0.8Al_12.2-PILC). The obtained Fe_0.8Al_12.2-PILCs were characterized by DR–UV–vis and IR spectroscopy, XRD, ESR, scanning electron microscopy and low temperature N₂ adsorption measurements. Important factors affecting catalyst activity and phenol removal efficiencies have been studied, i.e. the effect of pH, temperature, catalyst concentration and stability of the catalyst.     

VNS反应合成LLM-116

以1,3-二硝基吡唑为原料,经热重排、氨气中和得到3,5-二硝基吡唑铵盐,然后酸化得到3,5-二硝基吡唑。以三甲基肼碘化物（TMHI）作为异常亲核取代氢（VNS）反应试剂,与3,5-二硝基吡唑在叔丁醇钾为催化剂,利用VNS反应合成4-氨基-3,5-二硝基吡唑（LLM-116）。采用红外分析、核磁共振、元素分析等仪器鉴定了其结构,讨论了VNS反应机理及影响因素。通过实验,得出最佳VNS反应试剂为TMHI,反应时间为4h,反应温度为25℃,收率达到60%。     

LiMn2O4纳米粉的湿化学合成与表征

采用湿化学方法，通过水溶液中的化学反应直接合成纳米级LiMn2O4化合物，其结构基本上为无定型，但XRD图谱中已出现LiMn2O4特征峰，说明在水溶液中已初步形成尖晶石结构，运用XRD，SEM，TG－DTA等现代检测手段对样品的性能进行进行了表征，XRD及SEM等分析结果表明，合成样品经简单热处理后，晶型结构完善，形貌规整，均匀，比表面积积显著减小，粒度明显变粗。TG－DTA热分析证明，样品在低于900℃的温度下进行热处理时，仅发生LiMn2O4的晶化过程，产物的化学组成稳定，该法合成锂离子电池正极材料LiMn2O4，具有工艺流程简单，产物的成分，结构及粒度均匀等特点。     

国有化工流通企业的现状分析与发展对策

通过对国有化工流通企业现状的分析。了解其在计划经济与市场经济中的不同表现，并试图找到阻碍其生存与发展的症结所在，提出国有化工企业生存与发展的对策。     

缺陷交互作用对陶瓷半导体导电性能的影响

本文借助于缺陷化学反应过程，分析了陶瓷半导体内缺陷间的交互作用，得到了陶瓷半导体实验研究的三个重要启示：（1）强还原（或氧化）或施主（或受主）掺杂对同一样品不能同时起到最佳效果；（2）本征原子空位对施主或受主的补偿导致电导率的非线性增长；（3）缺陷的缔合降低了半导化杂质的有效浓度，从而使电导性能发生异常变化。