玻璃纤维介质中气溶胶粒子过滤效率研究

利用蒸汽冷凝法产生的不同粒径DOP（邻苯二甲酸二正辛脂）单分散气溶胶粒子及多分散气溶胶粒子，在滤材测试平台上对三种型号玻璃纤维滤材的过滤效率进行了研究。结果表明，滤材的过滤效率η与气溶胶粒子的粒径d密切相关，其中对d为0.1-0.3μm之间的气溶胶粒子过滤效率明显偏低；过滤阻力随比速v和串联的级数n增加而增大；相同滤材串联后，对单分散气溶胶粒子，各级过滤效率仍然相同，对多分散气溶胶粒子，各级过滤效率逐级下降，但级数越多，则总的过滤效率越高。     

玻璃纤维膜过滤特性研究

为将过滤器更好地应用于放射性气溶胶的清除,本工作利用邻苯二甲酸二辛酯（DOP）气溶胶团粒,对常用于制造过滤器的玻璃纤维膜进行了过滤特性研究。研究结果表明用玻璃纤维膜过滤清除气溶胶团粒时,对粒径在0.15～0.20μm之间的团粒较难清除;透过率随流速的增加而增加;单分散气溶胶团粒浓度变化对过滤效率的影响可忽略不计;多级过滤时,各单级过滤效率差异受多分散气溶胶的影响较大。     

微流体惯性撞击器气溶胶过滤行为研究

微流体惯性撞击器可作为安全壳过滤排放系统的第一级过滤装置，实现严重事故后安全壳快速泄压并对壳内放射性气溶胶进行初效过滤。为了探究惯性撞击器内气溶胶的过滤行为，开展可视化实验对气溶胶在惯性撞击器内的沉积分布进行研究。研究表明，可视化实验能反映撞击器内气流流向及气溶胶运动轨迹。气溶胶在过滤单元处的沉积位置主要集中在过滤单元的上表面及微流道的内壁面，过滤效率可达60%以上。同时，由于撞击器通道表面特性随气溶胶的沉积而改变，容尘条件下的气溶胶过滤效率逐渐增加。而当惯性撞击器内载气流速大于临界值时，过滤效率会因气溶胶的再悬浮而降低。     

用正反面计数率之比测定包括自吸收校正的滤材过滤效率因子 F

放射性工作场所放射性气溶胶监测是辐射防护工作中的一项极其重要的内容,目前大多采用滤材取样的相对测量法。要通过滤材取样测量空气中的气溶胶浓度,就必须定出包括自吸收校正在内的滤材过滤效率因子F。F与多种因素有关,且随测量条件而变化。下面介绍用正反面计数率之比测定F的方法。此法较为简便,而又不失现有方法的准确度。     

玻璃纤维滤料在氦气气氛中过滤效率和阻力的理论分析

针对空气和氦气介质,基于最易穿透粒径( MPPS)法和钠焰法,理论计算和分析了3种等级高效过滤材料的过滤效率及其阻力.研究结果表明:相对于空气介质,在同样滤速下,氦气介质中滤料的阻力降低,过滤效率大幅度提高；在同样滤速或颗粒直径下,随着温度升高,滤料阻力增大,过滤效率提高.     

国产滤材在气溶胶取样中的过滤特性研究

本文叙述利用天然氡、氢子体气溶胶测定滤材过滤特性的实验及其结果,给出国产滤材的过滤效率、阻力、自吸收系数、表面收集特性和大气灰尘堵塞速率等参数;分析比较了各类滤材的性能,提出选择使用滤材的建议,其中玻璃纤维型滤材具有较多的优点,更适合用于气载放射性物质取样。     

辐射监测气溶胶滤材过滤效率测试

采用双层滤膜采样法采集大气环境中的气溶胶,通过重量测量法、放射性核素测量法和特征元素测量法测量气溶胶采样滤膜对不同粒径颗粒物的过滤效率,利用这三种方法分别测试了两种常用滤膜的过滤效率。结果表明,不同类型滤膜的过滤效率存在明显差异;同一种滤膜对不同粒径颗粒物的过滤效率也有差别。     

鼓泡过滤可溶性气溶胶特性实验研究

池式鼓泡过滤是核电厂严重事故条件下一种重要的放射性气溶胶滞留过程。本文针对可溶性气溶胶在鼓泡过滤条件下的去除特性开展实验研究。结果表明,可溶性气溶胶会在鼓泡过滤过程中吸湿增长,尺寸增大,因此在评价可溶性气溶胶的去除效率时,必须保证上下游气溶胶处于干燥状态;另外,可溶性气溶胶的吸湿增长使得气溶胶的沉降特性发生改变,主要表现为原处于布朗扩散主导区的小粒径气溶胶会进入最易穿透区,效率降低,而原处于最易穿透区的气溶胶会进入惯性主导区,效率增加;气体流量的变化对气溶胶去除效率的影响不是单调的,与气-液两相流型以及气泡行为密切相关。实验结果可为验证和完善池式过滤气溶胶模型提供数据支撑。     

安全壳过滤排放系统实验用气溶胶的确定及相关参数的选取

为了满足安全壳过滤排放系统的气溶胶过滤性能测试实验的要求,进行实验用气溶胶选取的方案研究。对安全壳内气溶胶实际特性进行计算评估,得出严重事故后安全壳内气溶胶的特性随时间的变化规律。综合考虑分析结果和国外的研究成果,确定实验用气溶胶为BaSO4、TiO2。实验用气溶胶的配送压力为0.1~0.65 MPa;主管道浓度为50~900 mg/m3,气溶胶质量中值直径为1μm,粒径分布的几何标准偏差为1~2。     

固态气溶胶吸湿生长对过滤器检测效率的影响

本文使用加湿串联差分迁移分析仪（HTDMA）系统,研究了荧光素钠气溶胶在不同相对湿度（RH）环境中粒径的变化规律及对现场过滤效率的影响,且与NaCl气溶胶进行了对比。研究结果表明,荧光素钠气溶胶无潮解点,其粒径随相对湿度的增大而增大;NaCl有明显的潮解点,在小于75%相对湿度时,其粒径基本不变。随相对湿度的增加,直径为100 nm的荧光素钠测得的效率逐渐降低,而直径为100 nm的NaCl测得的效率在75%相对湿度以下时基本保持不变,但在大于75%相对湿度环境中大幅下降。因此,从气溶胶吸湿性能的角度来说,作为现场检测用的固态气溶胶,若保证环境相对湿度小于75%,NaCl和荧光素钠均可用于过滤器现场检测,且前者性能优于后者,但当相对湿度大于75%时,NaCl气溶胶已不能用于现场检测用途。     

Numerical simulation of a high velocity impact on fiber reinforced materials

Whereas the calculation of a high velocity impact on isotropical materials can be done on a routine basis, the simulation of the impact and penetration process into nonisotropical materials such as reinforced concrete or fiber reinforced materials still is a research task.

We present the calculation of an impact of a metallic fragment on a modern protective wall structure. Such lightweight protective walls typically consist of two layers, a first outer layer made out of a material with high hardness and a backing layer. The materials for the backing layer are preferably fiber reinforced materials. Such types of walls offer a protection against fragments in a wide velocity range.

For our calculations we used a non-linear finite element Lagrange code with explicit time integration. To be able to simulate the high velocity penetration process with a continuous erosion of the impacting metallic fragment, we used our newly developed contact algorithm with eroding surfaces. This contact algorithm is vectorized to a high degree and especially robust as it was developed to work for a wide range of contact-impact problems. To model the behavior of the fiber reinforced material under the highly dynamic loads, we present a material model which initially was developed to calculate the crash behavior (automotive applications) of modern high strength fiber-matrix systems. The model can describe the failure and the postfailure behavior up to complete material crushing.

A detailed simulation shows the impact of a metallic fragment with a velocity of 750 m s⁻¹ on a protective wall with two layers, the deformation and erosion of fragment and wall material and the failure of the fiber reinforced material.     

Dynamic heating and thermal destruction conditions of quartz particles in polydisperse plasma flow of RF-ICP torch system

Numerical simulation of turbulent mixing process of polydisperse quartz particle (particle size distribution in the range of 0.1–0.4 mm) flow with Ar and Ar-H₂ plasma generated by radio frequency inductively coupled plasma (RF-ICP) torch has been made. An approximate two-stage approach has been proposed to calculate the spatial–temporal distributions of temperature and resulting thermal stress in quartz particles during dynamic heating in polydisperse plasma flow. The influence of working gas compositions, particle size distributions, injection angle and flow rate of carrier gas on the thermal destruction conditions of quartz particles has been determined under different particle feed rates. It is found that all the solid quartz particles (0.1–0.4 mm) could be thermal destructed without overheating in RF-ICP torch system, when the hydrogen volume fraction in working gases is more than 1.5%–2% and particle feed rate is in a certain range. The values of the maximum and minimum feed rates have been determined under different hydrogen volume fractions. An optimal particle injection angle and flow rate of carrier gas is found around 50°–60° and 160–220 slpm, under which the value of maximum equivalent thermal stress in quartz particles is highest.     

亚化学计量UO2-x燃料芯块的制备机理

亚化学计量UO_2-x芯块是一种设计新颖的特殊核反应堆用核燃料,很难采用传统压水堆超化学计量UO_2+x+U芯块工艺进行制造。本工作采用UO_2+x+U混合粉末为原料制备了UO_2-x芯块,研究了铀粉表面包覆处理方法、铀粉含量、成型压力、烧结气氛等工艺参数对芯块O/U比、烧结密度和微观结构的影响,探讨了UO_2-x环形芯块的亚化学计量形成机理。研究表明,当铀粉加入量（质量分数）分别为0、3%、6%时,芯块O/U比分别为2.010、1.991、1.982,平均晶粒尺寸分别为10、15、20μm;当铀粉加入量为50%时,O/U比为1.943,样品发生熔化。亚化学计量UO_2-x芯块必须在干燥惰性气氛中密封保存。     

金属铱多孔材料过滤性能分析

金属多孔材料因其良好的过滤和理化性能，在气-固分离方面得到广泛的应用。采用氦质谱检漏仪、扫描电子显微镜及比表面积测试仪等对金属铱多孔材料的孔隙率、微观结构、孔隙特征及孔隙分布等方面进行了研究。研究表明，该金属铱多孔材料由粉体颗粒和孔隙组成，其内部孔隙相互连通构成复杂的三维结构；孔隙率约为16.93%，有98.7%的孔隙孔径为0.002~0.05 μm，1.3%的孔径为0.05~0.46 μm；根据多孔材料微过滤理论及气体中微粒捕集理论（不考虑多孔材料厚度），该金属铱多孔材料对粒径不小于0.46 μm粉体颗粒过滤效率达100%，且不受气体流速的影响；对粒径小于0.46 μm的粉体颗粒，当气体流速不大于5.28 m/s时，过滤效率同样达100%，而当气体流速大于5.28 m/s时，则会有部分粉体颗粒通过。多孔材料微过滤理论及气体中微粒捕集理论可为多孔材料过滤性能评价提供参考，该金属铱多孔材料也可用于放射性同位素材料的气-固分离。     

Analysis of the operating parameters of a vortex electrostatic precipitator

A vortex electrostatic precipitator(VEP) forms a vortex flow field within a precipitator by means of the vertical staggered layout of the double-vortex collecting plate facing the direction of the gas flow.The ion concentrations within the precipitator can be significantly increased.Correspondingly,the charging and coagulation rates of fine particles and particle migration velocity are significantly improved within the VEP.Since it can effectively collect fine particles and reduce precipitator size,VEPs represent a new type of electrostatic precipitator with great application potential.In this work the change curve of the external voltage,gas velocity,row spacing and effective collecting area influencing the precipitation efficiency were acquired through a single-factor experiment.Using an orthogonal regression design,attempts were made to analyze the major operating parameters influencing the collecting efficiency of fine particles,establish a multiple linear regression model and analyze the weights of factors and then acquire quantitative rules relating experimental indicators and factors.The regression model was optimized by MATLAB programming,and we then obtained the optimal factor combination which can enhance the efficiency of fine particle collection.The final optimized result is that:when gas velocity is 3.4 ms~(-1),the external voltage is 18 kV,row spacing is 100 mm and the effective collecting area is 1.13 m~2,the rate of fine particle collection is 89.8867%.After determining and analyzing the state of the internal flow field within the VEP by particle image velocimetry(PIV),the results show that,for a particular gas velocity,a vortex zone and laminar zone are distinctly formed within the VEP,which increases the ion transport ratio as well as the charging,coagulation and collection rates of fine particles within the precipitator,thus making further improvements in the efficiency of fine particle collection.     

Experimental investigation of solid–liquid mixtures freezing behavior in flow channels

The penetration and freezing of hot-core material mixtures through flow channels during core disruptive accidents (CDAs) within a sodium-cooled fast reactor is one of the major concerns confronting safety designers of the next-generation reactors. The main objective of this study is to investigate those fundamental characteristics of penetration and solidification involved in channeling molten metal and solid particle mixtures over cold structures. In this study, a low-melting-point alloy (viz., Bi–Sn–In alloy) and mixtures with solid particles (of copper and bronze) were used as a simulant melt, while L-shape metal (of stainless steel and brass) and stainless steel fuel pin bundle were used as cooling structures. Two series of basic experiments were performed to study the effect solid particles have on penetration and cooling behavior under various thermal conditions of melt by varying solid particle volume fraction, structure temperature and structural geometry. Melt flows and distributions were recorded using a digital video camera and subsequently analyzed. The melt penetration length into the flow channel and the proportion of melt adhesion on structural surfaces were measured. Results indicate that penetration length becomes shorter for molten-metal/solid particle mixtures (mixed melts) compared with pure molten metal (pure melt) as well as decreases with increasing solid particles volume fraction of the melt. The present study will contribute to a better understanding of the basic thermal-hydraulic phenomena of melt freezing in the presence of solid particles and to provide an experimental database for validation and improvement of the models of fast reactor safety analysis codes.     

铀铌合金表面热氧化膜结构研究

采用X射线光电谱分析技术、结合Ar离子枪溅射,研究了大气环境、不同温度(室温、100、200和300℃)条件下铀铌合金样品表面氧化膜结构的变化情况。实验结果表明:随温度升高,氧化膜厚度增大,氧化膜结构发生明显变化。不同温度热氧化处理后,铀铌合金初始表面Nb主要以Nb2O5形式存在,在Nb2O5与金属Nb之间,总存在一定厚度的NbO及少量其他价态氧化物NbOx(0x1,1x2)的混合层。室温～200℃热氧化合金样品表面铀均以含间隙氧的UO2+x(P型)存在,其U4f7/2结合能较UO2低约0.7eV。室温条件下,氧化膜成分主要为UO2;100、200℃热氧化后,氧化膜中除UO2外,还含有少量P型UO2+x,其U4f5/2卫星峰的结合能为396.6eV。300℃热氧化后的合金样品表面为铀的高价氧化物(U3O8或UOx,2x3),U4f特征峰的结合能分别为381.8和392.2eV;氧化层为UO2和金属铀的混合物。热氧化过程中,温度对铀氧化的影响较对Nb的明显得多。     

射频磁控溅射法制备氧化铝涂层绝缘性能及吸氢特性

氧化铝具有优良的绝缘和阻氚性能,是ITER候选功能材料之一。本工作采用射频磁控溅射法在中国低活化马氏体（CLAM）钢基底上制备了氧化铝涂层。分别采用掠入射X射线衍射、Raman激光光谱和原子力显微镜对氧化铝涂层的结构和表面形貌进行了表征;测量了氧化铝涂层体电阻率;研究了氧化铝涂层样品的吸氢特性。结果表明：氧氩比为0.1和0.5下制备的氧化铝涂层为非晶结构,氧氩比为0.4下制备的涂层中出现了结晶程度较差的氧化铝δ相结构;氧氩比为0.1和0.4下制备的涂层粗糙度和粒径均小于氧氩比为0.5下制备的涂层;不同氧氩比下制备的氧化铝涂层体电阻率均超过2.7×10¹⁴Ω•cm,氧氩比为0.4下制备的涂层电阻率最高,达到2.1×10¹⁵Ω•cm;氧氩比为0.5下制备的涂层样品具有最低的吸氢量。氧氩比对涂层的电绝缘特性和吸氢特性有显著影响。     

高燃耗陶瓷燃料颗粒的参数化建模及强度分析

弥散燃料芯体中的陶瓷燃料颗粒在辐照条件下会形成裂变气孔,燃料颗粒内部气孔间的相互干涉作用及气孔内压的增长致使局部拉应力超过材料强度极限,进而导致燃料颗粒开裂。本文考虑高燃耗燃料颗粒内气孔尺寸和位置分布的非均匀性,实现了颗粒内部的细观结构参数化建模。运用有限元方法计算并分析了气孔尺寸、基体约束压应力、温度和气孔分布方式对颗粒内部最大拉应力的影响,研究了颗粒内开裂危险区的分布规律。结果表明,陶瓷燃料颗粒最大拉应力随气孔尺寸和温度的增加而增大,随基体约束压应力的增加而减小;燃料相的断裂强度减小,开裂危险区面积增大;燃料颗粒从内部多处开裂破坏,而表层处开裂的概率更大。本文为弥散燃料失效研究及优化设计提供了分析方法及数值参考。     

化学气相沉积法制备ZrC涂层的热力学分析

ZrC涂层可能在新一代TRISO包覆颗粒上被用作阻挡裂变产物和承受主要载荷的关键层，是先进高温气冷堆燃料元件研究的一个重要方向。文章利用HSC-CHEMISTRY4.1软件分析化学气相沉积工艺参数对所制备的ZrC涂层的影响。分析结果表明，在载气中加入足够的氢气对制备单一ZrC涂层很有必要。ZrCl₄的转化率随着沉积温度的升高而增加，当温度过高时，其影响不明显；较佳的沉积温度范围为1400~1600℃。随着反应物浓度的增加，获得单一ZrC涂层对应的最低ZrCl₄与CH₄的摩尔分数比增加；反应物摩尔分数的最佳范围可选为：甲烷，1.0%～2.0%；ZrCl₄，为甲烷的1.5倍。