The effect of ageing temperature and time on the mechanical properties of Fe-NiCrMo alloys with different contents of δ ferrite

Laboratory cast alloys with 2–27% of δ ferrite were aged for up to 17,520 h in the temperature range 290–350 °C. Tensile and Charpy tests were performed at 22 and 290 °C on specimens aged for different times, and the microhardnesses of both constituents of the microstructure were determined for the alloy with 27% of δ ferrite. The effects of the content of δ ferrite, the ageing and testing temperature, and the ageing time on mechanical properties and notch toughness are presented and discussed.     

Comparison of microstructural properties and Charpy impact behaviour between different plates of the Eurofer97 steel and effect of isothermal ageing

The microstructure and fracture properties of the Eurofer97 steel plates of thickness 14 mm and 25 mm were investigated in as-received state and in state after long-term thermal ageing (550 °C/5000 h). Detailed microstructure studies were carried out by means of optical light, electron and quantitative electron microscopy. Mechanical properties were evaluated by means of Charpy impact testing and hardness testing and fracture surfaces were fractographically analysed in macro and microscales. The microstructure of the Eurofer97 consisted of tempered martensite with M₂₃C₆ and MX precipitates. Microstructure of 14 mm plate was more homogenous and fine grained than 25 mm plate. Due to different microstructure the t_DBTT of thicker plate was on +10 °C higher than for 14 mm plate for which reached −60 °C. Slight microstructural changes on the level of subgrain consisting of their partial recrystallization and slight carbide coarsening were observed after applied ageing. The isothermal ageing caused evident shift in t_DBTT about +5 °C, which was most likely caused by recrystallization of subgrains.     

联用紫外线辐射改性的羊毛织物茶色素同浴媒染工艺

以茶色素/金属媒染剂同浴媒染法为基础,对分别应用不同金属媒染剂的羊毛织物茶色素同浴媒染工艺进行筛选,对比经紫外线辐射改性前后的羊毛织物染色性能。结果表明,茶色素/铜媒同浴媒染的改性前后羊毛织物K/S值与固色率均较其余工艺高,并通过对比实验数据证实紫外线辐射有利于提升羊毛织物染色性能,故将其与茶色素/铜媒同浴媒染工艺联用进而增强茶色素染色效果。通过单因素分析对联用紫外线辐射改性的羊毛织物茶色素/铜媒同浴媒染工艺进行讨论并选择紫外线辐射改性时间、铜媒用量及染色时间等因子的优化范围,进而利用3因子二次通用旋转组合设计进行优化,从而确定优化工艺为(用量/对织物重(o.w.f)):紫外线辐射改性9 min,茶色素5.0%,铜媒1.7%,HCOOH 2.0%,pH=3.5~4.0,浴比1:50,95℃条件下染色60 min。与常规茶色素后铬媒染工艺相比,该优化工艺具有更好的染色效果和较低的金属媒染剂用量。     

Canadian regulatory approach to ensuring the implementation of effective ageing management programs for nuclear power plants

Effective ageing management is a key element of the strategy for maintaining long-term safety and reliability of nuclear power plants (NPP). This paper presents the Canadian regulatory perspective on managing the ageing of CANDU NPP. This paper looks introspectively at the current level of ageing management effort at Canadian reactor sites, and discusses the need to increase efforts in order to account for the increasing effects of degradation mechanisms. It examines accepted international practice for ageing management, making reference to International Atomic Energy Agency (IAEA) suggested practice, and goes on to describe the overall Canadian regulatory approach to ageing management, including the development of regulatory requirements for ageing management programs. In conclusion, the paper indicates a path forward involving a proactive ageing management approach.     

A statistically-engineered approach for assessing ageing effects on thermal-hydraulic elements for CANDU reactors

The purpose of this study was to develop a valid method to assess ageing effects on thermal-hydraulic elements for CANDU reactors. This method consisted of six steps. The ageing elements used in this method allowed for the immediate consideration of the code input without adjusting preexisting NPP simulation codes, and it also comprehensively considered the change in NPP’s thermal-hydraulic elements due to ageing effects. Each ageing element was selected from among the many thermal-hydraulic factors in which each element would have the greatest effect on the thermal-hydraulic conditions determined by the analysis of the ageing effect on the reactor. In this process, sensitivity analysis for each ageing element was done to understand the effects of each ageing element on the thermal-hydraulic conditions and peak cladding temperature. In addition, a degradation model capable of anticipating the values of the ageing elements over time was developed based on statistical interpretation methods and measured data, and the results’ conservativeness was guaranteed by conservatively selecting optimized combinations of ageing elements and their effects. The inherent uncertainty found in the complex nature of ageing for thermal-hydraulic elements can be reduced by being very conservative. Thus, the concept of the safety margin was introduced to propose a criterion for the assessment of ageing effects on thermal-hydraulic elements in NPPs. In addition, a preliminary analysis of Wolsong Unit 2 has been done. The results show that the 3rd highest value of PCT during LBLOCA was higher than that of the baseline with a value of 21.4 K. Thus, the ageing effect which is not taken into consideration in existing accident analysis evaluation methods was evaluated in this study. Moreover, it was found that meaningful differences may occur from the consideration of the safety analysis of NPP accidents. Accordingly, this method could synthetically assess the ageing effects on thermal-hydraulic elements in CANDU reactors, and this is expected to make considerable contributions to secure reliable safety margins for NPPs.     

Thermo-mechanical characteristics of UV-irradiated polyurethane elastomers extended with α, ω-alkane diols

A series of polyurethane elastomers were prepared by the reaction of poly ε-caprolactone and 4,4′-diphenylmethane diisocyanate. The prepolymer was extended using α, ω-alkane diols as chain extenders having 2-10 methylene units in their structure. The synthesized samples were irradiated for 50, 100 and 200 h in an ultra violet (UV) exposure unit. Modifications in the chemical structure before and after irradiation were characterized using Fourier Transform Infrared spectroscopy. The thermal and mechanical properties were affected by the ultra violet irradiation time and the number of methylene units in the chain extenders. The experimental results indicated that the morphological structure changed during irradiation as a consequence of hard segment and soft segment degradation.     

Displacement damage effects induced by fast neutron in backside-illuminated CMOS image sensors

ABSTRACT

BackSide-Illuminated (BSI) CMOS Image Sensors (CISs), with developed performance on quantum efficiency and sensitivity, have been applied for aerospace missions and gradually replaced FrontSide-Illuminated (FSI) CISs. Two types of BSI CISs with different epitaxial layer thicknesses were irradiated by 14-MeV neutron up to 3.40 × 10¹¹ n/cm² to analyze the degradation induced by neutron irradiation. Dark current, dark current distribution, full well capacity, and spectral response were tested before and after the neutron irradiation and at different annealing time points with various temperatures. The results were analyzed to characterize the degradation introduced by the unique backside passivation layer, and the converse illuminated direction. The interface states induced by displacement damage effects at the backside passivation layer were considered as a novel origin of dark current which was not involved in FSI CISs.     

Achievements and further plans for the OECD Halden reactor project materials programme

The materials programme at Halden, in addition to cladding corrosion studies, is aimed also at addressing the effects of operating conditions and water chemistry variables on core materials behaviour, particularly as related to reactor pressure vessel integrity and irradiation assisted stress corrosion cracking (IASCC), the materials degradation phenomenon which affects the structural integrity of stainless steel and nickel based components. The aim of the experimental work is to improve the understanding of materials ageing processes, to demonstrate the benefits of mitigation measures and to evaluate properties of materials, which have been subjected to long in-reactor service. While a number of the studies are performed in loops, which simulate light water reactor environments in terms of thermal-hydraulic, radiation and water chemistry conditions, dry irradiation facilities are also utilised, particularly in relation to studies aimed at determining the effects of fluence on material integrity.     

Effect of insulator environment on thermal ageing estimations for ethylene propylene rubber insulated nuclear power plant cables

Thermal ageing estimations merely focus on the degradation of cable insulator materials without considering their arrangement within the cable structure, by surrounding jacket or colorant pigments. This study reconsidered thermal ageing estimations based on the insulator elongation at break (EAB) degradation progress for flame retardant ethylene propylene rubber (FR-EPR) insulators within the whole cable structure. FR-EPR insulators were aged using two methods. In the first method, the insulators were heated, including jacket material at 125?°C, 150?°C, and 160?°C for 2208, 336, and 264 h, respectively. In the second method, the insulators were heated without jacket at 125?°C for 3480 h, and at 160?°C for 264 h. It was expected that the EAB degradation progress would be more severe when the FR-EPR insulators were aged without jacket. However, the results contradicted previous expectations, and the special heat-resistant polyvinyl chloride jacket accelerated the EAB degradation. In addition, the black FR-EPR insulators showed values that deviated from the predictions for the activation energy (E_a) and equivalent times compared to the white and red insulators due to the use of carbon black as a pigment. The reduced equivalent times for thermally aged FR-EPR insulators with jacket in this study were evident compared with the current degradation database for FR-EPR insulators degraded without jacket.     

PHEBUS FPT0~FPT2实验堆芯降级过程数值模拟

严重事故下,由于堆芯冷却剂丧失引起的堆芯裸露、过热和熔化过程对后期安全壳完整性、裂变产物行为等具有重要影响。法国辐射防护与核安全研究所主导的PHEBUS-FP研究项目旨在研究轻水堆严重事故下堆芯降级过程以及裂变产物行为。本文使用ATHLET-CD程序对PHEBUS-FP中的FPT0、FPT1和FPT2进行建模计算,主要分析堆芯过热,包壳氧化,堆内材料熔化、迁移及再定位过程。计算结果表明：不同蒸汽流量、不同加热功率将导致不同堆芯降级进程,在趋势上计算值与实验值吻合;模型的限制导致了部分计算值的偏差,本文讨论了包壳氧化与燃料再定位现象中的模型参数。     

Deposition Mitigation of the First Mirrors Exposed in EAST with Metal and Carbon Mixed Wall Materials

In order to investigate the effect of aperture geometry on deposition mitigation, stainless steel （SS） first mirrors （FMs） were fixed on the holders of protective aperture geometry with different depth-diameter ratios （DDRs） and exposed in the deposition dominated environment of EAST. A baffle was used during the wall conditioning. The surface properties and reflectivity of the FMs were characterized before and after exposure. It is shown that using aperture geometry and a baffle can effectively mitigate the impurities deposition. The degradation of the surface and specular reflectivity of the FMs is reduced with the increase of DDRs in the range of 0 to 2. The main contaminated elements in a low-Z and high-Z mixed wall materials environment were still carbon and oxygen.     

Influence of ageing heat treatment on alloy A-286 microstructure and stress corrosion cracking behaviour in PWR primary water

The influence of ageing heat treatment on alloy A-286 microstructure and stress corrosion cracking behaviour in simulated Pressurized Water Reactor (PWR) primary water has been investigated. A-286 microstructure was characterized by transmission electron microscopy for ageing heat treatments at 670 °C and 720 °C for durations ranging from 5 h to 100 h. Spherical γ′ phase with mean diameters ranging from 4.6 to 9.6 nm and densities ranging from 8.5 × 10²² m⁻³ to 2 × 10²³ m⁻³ were measured. Results suggest that both the γ′ phase mean diameter and density quickly saturate with time for ageing heat treatment at 720 °C while the γ′ mean diameter increases significantly up to 100 h for ageing heat treatment at 670 °C. Grain boundary η phase precipitates were systematically observed for ageing heat treatment at 720 °C even for short ageing periods. In contrast, no grain boundary η phase precipitates were observed for ageing heat treatments at 670 °C except after 100 h. Hardening by γ′ precipitation was well described by the dispersed barrier hardening model with a γ′ barrier strength of 0.23. Stress corrosion cracking behaviour of A-286 was investigated by means of constant elongation rate tensile tests at 1.5 × 10⁻⁷ s⁻¹ in simulated PWR primary water at 320 °C and 360 °C. In all cases, initiation was transgranular while propagation was intergranular. Grain boundary η phase precipitates were found to have no significant effect on stress corrosion cracking. In contrast, yield strength and to a lesser extent temperature were found to have significant influences on A-286 susceptibility to stress corrosion cracking.     

Effect of Low Pressure Nitrogen–Oxygen (N<Subscript>2</Subscript>/O<Subscript>2</Subscript>) Plasma Treatment on Surface Properties of Polypropylene Films

In this paper the effect of plasma treatment by using mixed gas (N₂/O₂) on surface properties of a Polypropylene PP films were investigated as a function of O₂ content and treatment time. Results obtained by using Fourier Transform infrared spectrometer (FTIR), contact angle measurement and scanning electron microscopy (SEM). It is found that plasma treatment can change chemical structure of polymer surfaces partially. SEM images revealed distinct changes in topography of PP due to O₂/N₂ plasma treatment. Finally wettability and surface energy before and after treatment investigated in different conditions.     

甲基乙烯基硅泡沫材料在复合条件下的辐射效应研究

为考察甲基乙烯基硅泡沫材料在不同条件下的辐射效应,开展了受压状态下材料经⁶⁰Co γ射线辐照后的热老化和湿热老化实验。采用扫描电镜、傅里叶转换红外光谱仪、固体核磁共振仪、万能材料试验机和蠕变松弛试验机等手段剖析了材料微观结构和宏观性能。结果表明,不同条件下老化后甲基乙烯基硅泡沫材料的泡孔有减小的趋势。²⁹Si交叉极化的NMR分析发现材料中有机硅链段峰的强度随吸收剂量的增大而升高,¹³C交叉极化的NMR分析表明γ射线辐照后材料的结构规整性有所降低。辐射后热老化样品的拉伸强度总比辐射后湿热老化样品的低,辐射老化和湿热老化的协同作用对材料的应力松弛率影响非常明显。     

150 keV质子辐照对GaAs子电池性能的影响

低能质子辐射会使电池产生较大的非电离能量损失,导致少数载流子寿命降低从而破坏GaInP/GaAs/Ge电池的电性能,其中尤以中间的GaAs子电池的衰减最严重。本文以卫星用主流GaInP/GaAs/Ge三结电池为研究对象,制备与三结电池中GaAs子电池相同尺寸结构和工艺的单结GaAs电池,以150 keV质子辐照后对其性能进行测试。测试结果表明,150 keV质子辐照后电池的量子效率衰减,且基区衰减最严重。光致发光测试结果显示,在3×10¹⁰、1×10¹¹、5×10¹¹ cm^-2辐照注量下,非辐射复合少数载流子寿命分别为2.22、0.67、0.13 ns。基于上述结果,利用多物理场仿真软件COMSOL建立了GaAs的物理模型,对GaAs子电池衰减进行仿真,将实验结果与模拟结果进行对比,两者电学参数的最大相对偏差为7%。仿真结果表明：中国空间站中电池的辐射衰减主要源于内辐射带中的质子,空间站轨道太阳能电池运行5 a,在太阳活动极大时,最大功率衰减约为7.6%,太阳活动极小时,最大功率衰减约为13.7%。     

BESⅢ漂移室定位子研制

报道第三代北京谱仪漂移室(BESⅢ DC)定位子的结构设计、制作生产及其基本性能.定位子是漂移室的精密部件,专用性强,结构精度高.产品按国标GB2829-2003,质量水平Ⅱ级验收.性能检验中高压绝缘性分长、中和短三种周期进行;湿度响应在自然变化和人工控制两种情况下观察;抗老化能力通过模拟老化实验前后性能比较得出.     

Scientific paradigms of structural safety of aged plants—Lessons learned from Russian activities

The study of the effects behind the degradation of components and materials is becoming increasingly important for the safe operation of aged plants especially when it comes to life extension. Since the Russian nuclear community began to examine life extension issues nearly 15 years ago, there is much to learn from these pioneering studies. At the Ninth International Conference entitled ‘Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment’ held in St. Petersburg, 2006, recent data were introduced regarding the ageing effects of mechanical properties of various kinds of steel and welding joints of Russian NPP components. The meeting was organized by the Central Research Institute of Structural Materials (CRISM) “Prometey” in cooperation with the IAEA and JRC-EU.In reviewing the recent data presented at the Ninth Conference, the authors believe that the paradigms of structural integrity issues in aged plants are now reasonably well established in (1) fracture mechanics and irradiation hardening of reactor vessels and core internals and (2) thermal ageing and annealing effects. However, the first author, G. Saji, believes that the current approach of low-cycle fatigue is still unable to prevent and predict environmentally assisted cracks such as demonstrated in the IGSCC issues in the down-comer pipes of RBMK plants and various steam generator corrosion issues. This fundamental flaw stems from design codes, which do not incorporate the basic knowledge of electrochemical corrosion mechanisms as represented by the corrosion current.     

氧气饱和条件下乙酰甲胺磷的60Coγ辐射降解研究

利用60Coγ辐射降解有机磷农药乙酰甲胺磷的稀水溶液,以乙酰胆碱酯酶抑制率为指标,研究了氧气饱和不同吸收剂量条件下乙酰甲胺磷稀水溶液辐照前后的毒性变化;并采用高效液相色谱、离子色谱、气-质联用等检测手段对降解产物进行了分析。结合溶液毒性变化和降解率、生成的无机离子浓度、降解产物结构分析等,初步推导了氧气饱和条件下乙酰甲胺磷的辐射降解机理。     

微波辐射纸浆多段漂白工艺研究

采用正交试验方法对纸浆多段漂白工艺中NaOH用量、辐射功率、碱处理时间及漂白工艺组合等因素进行了优化,并用红外光谱和纤维分析法对微波辐射纸浆漂白机理进行了研究。多段漂白的最佳工艺条件是:一段H2O2漂白,微波辐射功率240W,处理时间2.5min,H2O2用量5%,NaOH用量4%;二段NaOH碱处理,微波辐射功率200W,处理时间1min,NaOH用量3.5%;三段NaClO漂白,微波辐射功率240W,处理时间2.5min,NaClO用量4.2%,NaOH用量1%。在该工艺条件下,纸浆白度达78%ISO以上。红外光谱检测发现反应后木素的结构骨架大体上不起变化。纤维分析测定结果发现纸浆纤维形态基本上没有发生变化。     

Fitness for service assessment of degraded CANDU feeder piping—Canadian regulatory expectations

Allowance for the continued operation of feeder piping at some Canadian CANDU stations, which is experiencing active degradation mechanisms, has been based primarily on augmented inspection practices and conservative fitness for service assessments. The major degradation mechanisms identified to date are: pipe wall thinning due to Flow Accelerated Corrosion (FAC) and service induced cracking due to Intergranular Cracking due to Stress Corrosion Cracking (SCC) and potentially Low Temperature Creep Cracking (LTCC) mechanisms. Given that currently available industry codes and standards do not provide sufficient guidelines/criteria for assessing the degradation of feeder pipes, the Canadian Nuclear Safety Commission (CNSC) has asked the utilities to establish feeder pipe specific procedures to provide reasonable assurance that the risk associated with the feeder degradation is maintained at an acceptably low level. In response to this requirement, the Canadian CANDU industry has developed and continued to update feeder fitness for service guidelines to provide evaluation procedures and industry standard acceptance criteria for assessing the structural integrity of the feeder pipes. The scope and frequency of inspections are determined based on the results of the fitness for service assessments taking into account the relative susceptibility of feeder pipes to each specific degradation mechanism. While industry practices for the management of degraded feeder pipes have, in general, been complied with the regulatory expectations, outstanding issues still remain. Major regulatory concerns include uncertainties associated with limitations in both the inspection techniques and the mechanistic understanding of the degradation processes, which can impede inspection planning and fitness for service assessments.This paper presents the regulator's view of the current situation with respect to degradation of feeder piping, its implications for nuclear safety and the regulatory expectations on industry's management of the critical ageing phenomena.