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。     

220Rn子体源箱的数值模拟与性能优化

²²⁰Rn子体源箱是²²⁰Rn室可靠调控的重要组成部分,对其进行优化设计是建立高水平²²⁰Rn室的关键技术之一。本文在南华大学现有²²⁰Rn子体源箱和前期研究的基础上,采用计算流体力学方法建立了²²⁰Rn子体源箱数值模型,分析了入口流率、箱体轴向长度和换气率等对²²⁰Rn子体源箱性能的影响,进行了性能模拟结果与实验对比,最后开展了源箱的优化分析。结果表明：模拟和实验所获得的规律一致,模拟结果与实验结果相对误差保持在11%以内;增大入口流率能有效改善源箱²²⁰Rn子体的均匀性和稳定性,并增大源箱子体气溶胶的输出能力;当轴向长度一定时,入口流率均从1 L/min增加至10 L/min后,²²⁰Rn子体气溶胶浓度达稳定状态的时间最大可缩短66.41%,²²⁰Rn子体气溶胶活度输出率最大可增加20.25%,²²⁰Rn子体源箱的均匀性先变差后变好,且在入口流率为4 L/min时均匀性最差;增加源箱轴向长度对²²⁰Rn子体的均匀性和稳定性影响不明显,但能有效提高²²⁰Rn子体气溶胶活度输出率;当入口空气流率设置为1~10 L/min且保持不变时,轴向长度从100 cm增至140 cm,²²⁰Rn子体气溶胶浓度达稳定状态的时间变化不明显,²²⁰Rn子体气溶胶活度输出率最大可增加48.51%,²²⁰Rn子体源箱的均匀性先变差后变好。     

高效过滤器现场试验荧光素钠法中采样滤膜的性能研究

根据荧光素钠法的采样要求,建立了以荧光素钠为气溶胶介质的采样滤膜性能测试装置和方法,实测了7种玻璃纤维滤膜的阻力、本底荧光值及流速0.92~2.75 m/s下的过滤效率,并分析了各种滤膜性能对过滤器净化系数检测结果的影响。结果显示,滤膜本身过滤效率对高效过滤器系统净化系数的影响较小,其中的CF-A、FP5211、GC90滤膜的相对误差分别为0.014%、0.063%、0.082%;浸泡液浓度较低时,本底荧光值对系统净化系数的影响比较明显;而阻力过大限制了滤膜上荧光素钠的收集量,进而相对增加了本底荧光值的干扰。研究结果可以为采样滤膜的评价、选择、使用提供指导。     

旋风组钠气溶胶去除系统性能验证

钠气溶胶是钠冷快堆发生钠火时产生的特征性产物,需通过除尘净化系统对钠气溶胶进行去除净化,以减少排放到环境的放射性剂量和钠气溶胶浓度。采用干式气固分离路线,设计了一套旋风组钠气溶胶去除系统,通过开展真实钠火环境下的钠气溶胶去除试验,考察了金属钠燃烧过程中钠气溶胶浓度变化、粒径分布、压降、去除效率等主要参数,最终认为该系统对钠气溶胶具有很高的去除效率。     

废水组分对离子交换树脂处理含铀废水的影响

采用静态吸附和动态柱式实验相结合的方法,研究含铀废水中其它组分对201×7强碱性阴离子交换树脂处理含铀废水工艺过程除铀性能的影响。实验结果表明：溶液中存在的常量阴离子、三乙醇胺和机油等不同程度影响树脂的交换效率或降低树脂的工作交换容量。当溶液中c(CO^2－₃)≥0.24mol/L、c(HCO^－₃)≥0.28mol/L、c(SO^2－₃)≥0.23mol/L、c(Cl^－)＞0.09mol/L时,出水铀质量浓度大于20μg/L;树脂可允许通过的最大三乙醇胺浓度不应超过250mg/L;树脂中机油含量大于1%时,树脂的工作交换容量下降16%;树脂中机油含量大于11%时,树脂几乎完全失效。     

气溶胶中钋-210的分析

采用α能谱示踪法进行了大气气溶胶中的210Po分析方法研究。气溶胶滤膜样品经剪碎后加入209Po示踪剂,在硝酸-硫酸-高氯酸体系中湿式消化,用0.5 mol/L盐酸反复浸取,在高温高速搅拌的水浴中置入银片自沉积,样品源银片在α能谱仪上测量。建立的分析测量方法,对于采样体积大于500m3的气溶胶样品,探测下限可达0.01 m Bq/m3,回收率接近95%。本方法经多项质量控制措施验证,现已在国家辐射监控点大气气溶胶测量和铀矿污染源监测项目中得到应用。     

硬塑料管道对气溶胶取样结果的影响

本文报告硬塑料长取样管道对气溶胶取样结果的影响。实验用气溶胶的质量中位空气动力学直径为7.1μm,几何标准偏差为1.9。气溶胶分别经φ30mm 和φ50mm 的15m 长管道(均包括5个弯头)后,其质量浓度发生了变化,层流时(30L/min)分别降至原来的14.5%和6.4%,紊流时(100L/min)分别降至原来的21.3%和15.4%;气流中粒谱也发生变化,使小于4μm 的粒子的质量份额增加4倍左右。文中还简单介绍了测定壁沉积份额和粒谱变化的方法,并对取样管道的选择和应用中的有关问题进行讨论。     

水浴除尘器对钠气溶胶除尘效率试验研究

本文介绍了中国实验快堆钠工艺间事故通风系统使用的水浴除尘器的结构、除尘原理,试验流程的设计等。通过试验研究测量了不同风量条件下水浴除尘器的除尘效率,分析了影响水浴除尘器除尘效率的因素。试验结果表明,水浴除尘器在特定条件下,对钠气溶胶除尘效率效果较好。该试验研究结果对快堆核电站除尘设备选择及除尘系统的设计有参考价值。     

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。     

高效过滤器钠焰效率试验中NaCl浓度对测量精度的影响

在核级高效过滤器钠焰效率试验中,使用自制的稀释装置和研制的钠焰光度计,试验测量了NaCl浓度在4 ng/m³～13 mg/m³范围内,气溶胶燃烧光强与浓度之间的关系,然后用最小二乘法对测量值进行曲线拟合。研究结果表明：低浓度区,光电流与NaCl浓度间为线性关系,光谱的自吸收系数为1;中、高浓度区,光电流与NaCl浓度间不再符合线性关系,光谱的自吸收系数随浓度的增加而减小。研究结果要求：在高效过滤器效率测量时,如果使用国标的效率计算公式,须保证NaCl的原始浓度低于0.05 mg/m³;如果原始浓度高于0.05 mg/m³,则需使用实际标定的光电流与NaCl浓度间的关系曲线来代替国标的效率计算公式。     

自吸式文丘里水洗器结构设计程序开发

开发了1套自吸式文丘里水洗器结构设计程序,该程序给出了完善的热工参数计算和喉部结构设计逻辑。在实验研究的基础上,提出了阻力计算修正关系式,修正后的计算结果与实验值的相对误差在8.6%以内。     

自吸式文丘里水洗器阻力特性实验研究

以空气、水为工作介质,对自吸模式运行的有机玻璃文丘里水洗器阻力特性进行了实验研究。研究结果表明,经验公式计算值与实验结果的趋势较为一致,但相对偏差较大,高达±50%以上。在实验的基础上,给出了阻力计算实验关联式,计算值与实验结果符合很好,相对偏差在±15%以内。     

Numerical analysis of thermal plasma scrubber for CF4 decomposition

CF₄ gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse gas. It must be removed or converted safely due to its extreme toxicity. Although a CF₄ decomposition system using a thermal plasma scrubber was commercialized, its removal efficiency is limited. In this work, a numerical analysis of CF₄ decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition environment. The decomposition and recombination temperatures of CF₄ were analyzed using thermodynamic equilibrium calculations. The chemical reaction of CF₄ decomposition into carbon and fluorine gas was considered in this numerical analysis. The injection position and angle of the CF₄ were controlled in order to enhance the decomposition rate. The vertical injection of CF₄ near the torch exit improved the mixing of the CF₄ with the thermal plasma flame. In addition, it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped reactor. As a result, it is revealed that the CF₄ injection location and the reactor configuration are the most important factors in improving the decomposition rate.     

Experimental research on aerosols collection performance of self-priming venturi scrubber in FCVS

The self-priming venturi scrubber is the key component of filtered containment venting system to removal radioactive products during severe accident in nuclear power plant. In this paper, the collection performance of aerosols in the venturi scrubber is researched with experiment. The results indicate that the retention performance is closely related to the operating conditions and structures, and this relation is more closely for the removal of particle size under 0.5 μm. The retention efficiency in a venturi scrubber increase with improving of both gas velocity and injection flow rate, and the influence of gas velocity on efficiency is more effective at low injection flow rate. The venturi scrubber with a long throat length or small diffuser angle performs excellent retention performance for small size aerosols. In condition of gas velocity higher as U_avg = 200 m/s and the sufficient injection flow rate, the retention efficiency maintains upon 99% for the aerosol that size range from 0.1 μm to 10 μm. The pressure loss of the venturi scrubber increase slightly with extending the length of throat, and also with reducing diffuser angles. The removal efficiency is usually at the expense of the energy loss, while the higher aerosol retention efficiency corresponds to bigger pressure loss.     

Structure design on improving injection performance for venturi scrubber working in self-priming mode

The venturi scrubber working in self-priming mode is one of the most efficient gas cleaning devices to remove the radioactive particles and gases from gaseous stream during severe accident in nuclear power plant. This paper focus on improving injection performance in a split type self-priming venturi scrubber, the static pressure distributions at gas and liquid channels in the scrubber are studied emphatically, the experimental results indicate that pressure at the center of nozzle exit is lower than at the wall, and the variation laws in radial are different with increasing gas velocity. When the average gas velocity at throat U_avg = 64.3 m/s, the static pressure difference between center and wall is 2.1 KPa; with the increase of gas velocity, pressure at centre and wall reduce gradually and the pressure difference become significantly, when the average gas velocity U_avg = 225.8 m/s, pressure at the center is lower 23.2 KPa than at the wall, relative deviation is about 45.6%. However, when U_avg ≥ 230 m/s, the static pressure is not continue to decrease but reverse to recover with increasing gas velocity, and recovery rate at the wall is greater than at the center. The condition before the transition point (U_avg < 230 m/s) is defined as velocity dominate area, in this area, pressure will always decrease with increasing gas velocity; the condition after the point (U_avg ≥ 230 m/s) is defined as resistance dominate area, while pressure in this area will reverse to recover, the venturi scrubber design should be ensured in velocity dominate area. The injection performance of self-priming venturi scrubber is closely relate to pressure distribution characteristics at nozzle exit, in condition of no injection or injecting air, pressure at liquid channel is consistent with the pressure at the wall of nozzle exit, which is higher than the average static pressure; when injecting water, an additional pressure increment will generate at liquid channel duo to the momentum exchange between gas and liquid, and lead to the effective pressure difference for injection reduce further. On this occasion, the influence of liquid channel area and resistance coefficient on injection performance become important, increase liquid channel area is effective for improving injection flow rate.     

Visualized measurement of extremely high-speed droplets in Venturi scrubber

Venturi scrubbers for filtered venting have been installed in nuclear power plants worldwide. Venturi scrubbers can eliminate fission products from a polluted gas by interaction through gas–liquid interfaces. Therefore, droplet diameter is important from the viewpoint of decontamination. When Venturi scrubbers are used in severe accidents, the gas flow velocity might be extremely high. In these studies, the authors did not measure droplet diameter under extremely high gas velocity conditions. In the scenarios, experimental data pertaining to droplet diameter, under the extremely high gas flow velocity, are required. Therefore, this objective is to evaluate the diameter of extremely high-speed droplets. A visualization experiment was conducted using a Venturi scrubber. The droplet diameter distribution and the Sauter mean diameter (SMD) were determined. By comparing between the experimental value of SMDs and the one evaluated using Nukiyama–Tanasawa equation, it was confirmed that the Nukiyama–Tanasawa equation can be used to evaluate SMD with good accuracy in the gas velocity range of 82–250 m/s, except the highest gas velocity conditions. Furthermore, the droplet generation mechanism in the Venturi scrubber was considered to clarify the main reason why the Nukiyama–Tanasawa equation can be used to evaluate SMD droplet diameter.     

Approaches for Reducing Carbon-14 Stack Emissions from Korean CANDU® Nuclear Power Plant

Relatively high carbon-14 emissions, which occurred at Wolsong Nuclear Power Plant during 1998 and 1999, made the site staff to implement several operational improvements: (1) restriction of the maximum in-service time of moderator ion exchange (IX) resin columns to 80 days, (2) discontinuation of the practice of re-using ‘used’ IX resin columns for removing the gadolinium nitrate at star-up, and (3) reduction of the frequency and volume of the moderator cover gas purging through increased O₂ additions to the cover gas. In this way, the emission rates returned to normal levels during the remainder of 1999 and 2000. To optimize the use of the moderator IX resin column, the special surveillance was carried out at Wolsong Unit 3. This showed that only the ¹⁴C stack emission data were a practical indicator for exhaustion of IX resin column. From this data, a criterion was derived: IX resin column can be put in service for 100 days unless a ¹⁴C emission rate higher than about 20GBq-month^-1 (0.4Ci-month^-1) takes place for two consecutive weeks. Finally it was suggested that using a portable ¹⁴C scrubber could benefit for reducing the ¹⁴C stack emissions, especially those due to leakage of the moderator cover gas.     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.