“华龙一号”核电厂烟囱气态流出物取样系统验证的试验与分析

目的 通过试验验证以确保中国自主研发的第三代压水堆核电站"华龙一号"堆型烟囱气态流出物取样系统（采用单嘴取样头设计）充分满足取样代表性要求。方法 本文基于美国国家标准ANSI/HPS N13.1-1999要求,建造了"华龙一号"反应堆烟囱1：5的比例模型,在比例模型上完成了3个不同标高取样截面的平均气旋角、气体流速分布、示踪气体分布、示踪气溶胶分布验证试验,并在福清核电站1、2号机组的烟囱上开展了气旋角、气体流速、示踪气体浓度分布的验证试验。结果 在"华龙一号"比例模型烟囱三个预选取样截面（Q1、Q2、Q3）中心2/3区域内,在两种设计通风工况下,气体流速分布变异系数（COV）≤ 1.1%,所有测点最大气旋角为11.38°,示踪气体分布浓度分布COV ≤ 4.4%,示踪气溶胶浓度分布COV ≤ 4.7%;在实际烟囱预选取样截面中心2/3面积内气体流速分布COV ≤ 8.4%,所有测点气旋角平均绝对值为11.3°（且最大值<20°）,并且由DVN碘排风、DVN正常排风系统注入示踪气体时,测量截面上示踪气体浓度分布COV分别为2.2%、1.3%。结论 "华龙一号"模型烟囱和实际烟囱的所有测试指标,全部符合ANSI/HPS N13.1-1999标准对于取样截面上污染物混合均匀性的要求,即可以采用单点取样方式来设计"华龙一号"烟囱气态流出物取样系统。     

祛毒止痒汤

我身痒起红斑几天,极其难受,上医院检查,诊前因咽痛、咳嗽服磺胺。医院体检结果为:背、双手腕、指背见数片直径为1～4cm之圆形水肿性红斑。诊断:同定性红斑型药物性皮炎。医生于是给我开予处方:银花     

双源CT在肺栓塞与下肢深静脉血栓形成联合成像中的应用价值

目的：探讨第二代双源CT一次性造影在肺栓塞（PE）与髂股深静脉血栓形成（DVT）联合成像中的应用价值。方法共185例临床疑诊PE的患者进行了双源CT肺动脉造影和深静脉造影联合成像检查。肺动脉扫描采用单能量大螺距采集模式,髂股静脉扫描采用双能量技术。结果185例中28例（15.14%）患者同时患有PE及DVT,8例（4.32%）患者仅有PE而没有DVT,7例（3.78%）患者仅有DVT而没有PE。PE的直接征象表现为肺动脉管腔内大小不等、形态多样的充盈缺损和管腔完全阻塞影像。DVT表现为管腔中央类圆形、长条形不均匀低密度性充盈缺损。结论双源CT一次性联合成像在肺栓塞与髂股深静脉血栓形成中具有较高价值,适用于伴有下肢静脉循环障碍的可疑肺栓塞患者。     

巨大淋巴结增生症的CT诊断

目的探讨巨大淋巴结增生症(CD)的CT诊断价值。方法对经手术及病理证实的24例巨大CD的CT表现进行研究、分析。24例中,局限型透明血管型CD 23例、弥漫型CD 1例。结果24例CD,病变表现为圆形、类圆形或分叶状较大的单发软组织密度肿块影,边界多清楚锐利,直径3~15 cm。结论 CT平扫加增强扫描有助于对CD明确诊断和鉴别诊断,CD肿块以动脉期显著强化和延迟期的持续强化为特征性表现;胸、腹部局限型CD以较大孤立性无坏死、出血肿物、均匀性明显强化、或中央伴有分支状钙化为特征。     

腮腺混合瘤超声误诊分析

目的回顾总结腮腺混合瘤声像图特点及其误诊原因,提高诊断准确性。方法回顾性观察70例腮腺肿块的声像图表现,与术后病理对比分析。结果 70个病灶均为腮腺浅叶的边界清楚、后方回声增强的低回声肿块,其中圆形或椭圆形66个,分叶状4个;实质均匀性28个,实质非均匀36个,混合性6个;周边型血供33个,门型血供9个,乏血供型5个,17个血供无特殊;病理提示混合瘤42个,其它良恶性肿块28个。结论超声以二维声像图及血供特点做综合分析,对腮腺混合瘤有一定的诊断价值,但有些病例的声像图与混合瘤具有共性特点而易误诊,应予注意鉴别及定期随访复查。     

CT在胃肠道间质瘤诊断中的价值分析

目的分析螺旋CT对于胃肠道间质瘤的CT表现特征,探讨CT对胃肠道间质瘤的临床应用价值。方法回顾性分析2 0 0 8年3月—2 013年3月来我院就诊经手术和病理证实的胃肠道间质瘤患者共计31例,术前经螺旋C T平扫和增强扫描,分析其CT扫描所表现出来的临床特征。结果 31例患者中,食道1例,胃21例,小肠6例,结直肠2例,肠系膜1例。CT表现为腹腔或盆腔内圆形、类圆形或浅分叶软组织肿块,直径2.8~18.7 cm,良性7例,交界性6例,其余均为恶性,其中肝转移4例,平扫密度均匀或不均匀,增强扫描肿块部分均匀或不均匀轻、中度强化,其中2例显示形态不规整。CT针对31例患者病灶能精确定位或粗略定位。结论通过CT检查,针对胃肠道间质瘤的良恶性判定以及病灶区域定位、有效的观察肿瘤与其周围组织结构关系,螺旋CT有着较高的使用价值,可有效对临床治疗方案的确立以及患者预后的评估提供科学依据。     

肺炎性假瘤的CT、X线表现分析

目的探讨肺炎性假瘤的X线、CT表现及其特征。方法搜集61例经手术病理证实的肺炎性假瘤的CT、X线资料进行了分析研究。结果主要影像表现:①类圆形大都边缘光整的肿块,多为单发,直径在3.0cm左右,密度均匀。②局限性胸膜肥厚粘连,无胸水及钙化征象,肿块与增厚的胸壁之间有条状低密度影。③病变中间层面一侧边缘垂直于胸膜呈刀切样改变。④病灶边缘粗短毛刺。⑤肿块内空洞坏死。结论全面分析假瘤的影像学特征,重视病人肺内感染病史,对提高诊断准确率很有必要。     

切除一侧卵巢会影响怀孕吗

27岁的婉茹体检发现右侧卵巢畸胎瘤6个月,医生要求其手术住院治疗。婉茹已婚,无生育史,平素月经规律,经量中等,轻微痛经。通过查体发现右侧附件区可触摸到直径5厘米大小囊实性、边界清楚、活动正常的肿物,无压痛。盆腔B超提示子宫前位,大小正常,肌层回声均匀,子宫内膜5毫米,右侧卵巢内5.6×5.5厘米大小的混合回声,考虑是畸胎瘤。     

支气管囊肿的CT诊断及鉴别诊断

目的 :探讨CT在支气管囊肿鉴别诊断中的价值。方法 :选取我院经手术及病理证实的支气管囊肿18例患者的CT资料进行回顾性分析。结果:18例患者中,5例为纵膈型支气管囊肿,其中2例为囊性,3例为软组织密度,CT值12-56HU,增强后未见强化。13例为肺内型支气管囊肿,直径0.5~5.5CM,平均3.5CM。13例中含气囊肿3例,1例呈薄壁圆形空腔,2例呈分叶状偏心空腔;含液囊肿4例,2例呈卵圆形,1例呈多房分隔状薄囊,增强后囊壁及囊内分隔均有强化,囊内容物未见强化;1例呈边缘模糊的厚壁球形病灶,囊内密度不均匀。软组织密度肿块6例,2例位于左肺下叶,1例肿块呈小结节状伴边缘环形钙化,3例为边缘模糊的不规则肿块。结论:CT扫描对于含气、含液支气管囊肿具有较高的诊断价值,对于软组织密度支气管囊肿的鉴别诊断较困难。     

局灶性脂肪肝的超声诊断

目的探讨局灶性脂肪肝的声像图特点。方法对39例确诊为局灶性脂肪肝患者的声像图表现进行回顾性分析。结果根据声像图表现分为三种类型:(1)弥漫性非均匀浸润型 23例,占58．97％,肝实质回声弥漫性增高,其内出现一个或多个低-弱回声区,边界尚清晰,形态呈楔形、长条形或类圆形。(2)叶段性浸润型12例,占30．77％,以肝叶段为界,呈大片不规则状的高回声区。(3)局灶性浸润型4例,占10．26％,表现为肝内小片状高回声光团,单发或多发,边界清晰,外形不规则。结论超声能够根据声像图表现,作出局灶性脂肪肝的诊断,但必须注意与肝内良、恶性肿瘤相鉴别。     

Mixing in a square and a rectangular duct regarding selection of locations for extractive sampling of gaseous contaminants

Tests were conducted to characterize the uniformity of velocity and tracer gas profiles in a square and a rectangular duct with respect to defining the suitability of locations for single point sampling of gaseous contaminants. Several configurations, such as a straight duct with unidirectional flow at the entrance section and straight ducts preceded by mixing elements (a 90 degrees mitered bend and double 90 degrees bends in S- and U-type configurations) were tested. Results are compared with those from circular ducts. For a straight duct of square cross section, which is not preceded by a mixing element, the coefficients of variation (COV) of tracer gas concentration at 19 duct diameters downstream of the gas release location is 143% (center release of tracer gas). COVs of velocity and tracer gas concentration in a straight square duct 9.5 duct diameters downstream of a 90 degrees mitered bend are 6% and 24.3% (top inside release), respectively, which does not meet the ANSI N13.1 limit of 20% for the tracer gas COV. In case of the rectangular duct with a 3:1 (width to height) aspect ratio, COVs of velocity and tracer gas concentration at 9 duct diameters downstream of a 90 degrees mitered bend are 29% and 62% (bottom inside release), respectively. A mixing element in a square duct comprised of two 90 degrees mitered bends in a U-configuration produces results similar to those obtained with a single 90 degrees bend. However, COVs of velocity and tracer gas concentration in a square duct 6 duct diameters downstream of an S-type double bend are 10.6% and 8.3% (top inside release), respectively, which comply with the ANSI tracer gas and velocity criteria for single point representative sampling. When mixing elements were employed in square ducts, the COV results were comparable with those of other researchers for circular ducts.     

Evaluation of mixing downstream of tees in duct systems with respect to single point representative air sampling

Air duct systems in nuclear facilities must be monitored with continuous sampling in case of an accidental release of airborne radionuclides. The purpose of this work is to identify the air sampling locations where the velocity and contaminant concentrations fall below the 20% coefficient of variation required by the American National Standards Institute/Health Physics Society N13.1-1999. Experiments of velocity and tracer gas concentration were conducted on a generic "T" mixing system which included combinations of three sub ducts, one main duct, and air velocities from 0.5 to 2 m s (100 to 400 fpm). The experimental results suggest that turbulent mixing provides the accepted velocity coefficients of variation after 6 hydraulic diameters downstream of the T-junction. About 95% of the cases achieved coefficients of variation below 10% by 6 hydraulic diameters. However, above a velocity ratio (velocity in the sub duct/velocity in the main duct) of 2, velocity profiles were uniform in a shorter distance downstream of the T-junction as the velocity ratio went up. For the tracer gas concentration, the distance needed for the coefficients of variation to drop 20% decreased with increasing velocity ratio due to the sub duct airflow momentum. The results may apply to other duct systems with similar geometries and, ultimately, be a basis for selecting a proper sampling location under the requirements of single point representative sampling.     

Suitability of air sampling locations downstream of bends and static mixing elements

The revised standard for sampling effluent air from stacks and ducts of the nuclear industry places limits on the non-uniformity of velocity and contaminant profiles at the sampling location; namely, the coefficients of variation must not exceed 20% over an area that encompasses at least the center 2/3 of the cross sectional area. Tests were conducted to characterize the degree of mixing at downstream locations as affected by several types of flow disturbances, including 90 degree elbows and commercial static mixing devices. Flow straighteners were incorporated into the ducting upstream of the mixer to be tested to simulate the dampening of flow turbulence that might occur because of upstream HEPA filters. The coefficients of variation of velocity and tracer gas concentration measured in a straight tube at a distance of 3 diameters downstream from a 90 degree elbow were 17% and 69%, respectively. The mixing is impacted by the upstream flow turbulence. Without a flow straightener, the tracer gas concentration coefficient of variation was reduced to 33% at the 3-diameter location. The use of static mixing elements can greatly enhance the mixing process. A ring placed just downstream of a 90 degree elbow, which blocks the outer 56% of the cross sectional area, results in a coefficient of variation of 19% for tracer gas concentration at the 3-diameter location. Pressure loss across the elbow with the ring is about nine times that of the basic elbow. One of the commercially available static mixers provides coefficients of variation that are less than 10% for both velocity and tracer gas concentration at 4 diameters downstream from the mixer with a pressure loss that is only about 3.5 times as large as that of a 90 degree elbow.     

核电厂应急行动水平中“气载流出物异常”类EAL制定的探讨

目的 对制定核电厂应急初始条件和应急行动水平（ICs/EALs）中的"气载流出物异常"类应急行动水平的相关问题进行探讨。方法 针对制定核电厂气载流出物类应急行动水平中必须注意的关键问题逐一进行了分析、讨论。结果 分析表明,延迟释放时间、核素释放份额、导出EAL单位变换等问题均会影响“气载流出物异常”类应急行动水平的导出结果。结论 气载流出物异常类应急行动水平的优先级较低而不适合作为决策的唯一判据,但其作为体现EAL多样性的一种指标,能够反映某些潜在事件的征兆。     

Use of tracer gas technique for industrial exhaust hood efficiency evaluation--where to sample?

A tracer gas technique using sulfur hexafluoride (SF6) was developed for the evaluation of industrial exhaust hood efficiency. In addition to other parameters, accuracy of this method depends on proper location of the sampling probe. The sampling probe should be located in the duct at a minimum distance from the investigated hood where the SF6 is dispersed uniformly across the duct cross section. To determine the minimum sampling distance, the SF6 dispersion in the duct in fully developed turbulent flow was studied at four duct configurations frequently found in industry: straight duct, straight duct-side branch, straight duct-one elbow, and straight duct-two elbows combinations. Based on the established SF6 dispersion factor, the minimum sampling distances were determined as follows: for straight duct, at least 50 duct diameters; for straight duct-side branch combination, at least 25 duct diameters; for straight duct-one elbow combination, 7 duct diameters; and for straight duct-two elbow combination, 4 duct diameters. Sampling at (or beyond) these distances minimizes the error caused by the non-homogeneous dispersion of SF6 in the duct and contributes to the accuracy of the tracer gas technique.     

Effect of conveyance pipe dimension and orientation on mosquito oviposition in a simulated stormwater management device

Simulated stormwater management devices baited with alfalfa infusion were constructed to test conveyance pipe dimension and orientation as a potential deterrent to mosquito oviposition. Various configurations of pipe diameter, length, and orientation were evaluated based on egg raft counts. Field trials tested pipes of 1.3-, 5-, and 10-cm diam and 0-, 90-, or 270-cm lengths, in both horizontal and vertical orientations. Additional trials of 10-cm-diam horizontal pipe evaluated the effects of a 90 degrees bend, single or dual entry points, and lengths greater than 270 cm. Significantly fewer egg rafts were collected in pipes of smaller diameter and longer length in both horizontal and vertical orientations. A 90 degrees bend or removal of an entry point to pipes of fixed length had no significant effect on oviposition. A maximum tested length of 24.4 m did not preclude oviposition. The results of this study suggest that manipulating diameter and length of conveyance pipe in stormwater management devices may not be an effective strategy to deter oviposition. The need for integrating improved, novel, nonchemical mosquito control measures into designing and operating stormwater management structures is discussed.     

A simple and inexpensive method for determining the effective ventilation rate in a negatively pressurized room using airborne particles as a tracer

The ventilation rate within a negatively pressurized room is usually determined by measuring the exhaust air flow rate. This method does not account for air mixing factors and gives limited information on ventilation efficiency within the room. Effective ventilation rates have been determined using tracer gases such as sulfur hexafluoride (SF6). The objective of this study was to determine whether artificially generated airborne particles could be used as a tracer to directly measure ventilation efficiency. We monitored the decay of artificially generated particles within negatively pressurized rooms. Separate trials were conducted at air exhaust rates ranging from about 6 to 20 room air changes per hour. Particles were generated to a minimum of 20 times the ambient concentration using a simple ventilation smoke bottle and measured with handheld light-scattering airborne particle counters. Data were obtained for aerodynamic particle size ranges of: 0.5 micron (microM) and larger, and 1.0 microM and larger. The time rate of decay of particles was plotted after subtracting the background concentrations. Results were compared with simultaneously conducted tracer gas decay analyses (ASTM method E741-95) using SF6. Particle concentrations followed an exponential decay (R2 = 0.98-0.99+) and mirrored the decay curve of the tracer gas. The air change rates predicted by the particle count procedure differed from the tracer gas results by a mean of 4.0 percent (range 0%-12%). The particle count procedure was substantially simpler and less expensive than the SF6 tracer gas method. Additional studies are needed to further refine this procedure and to explore its range of applicability.     

The use of tracer gases to determine dust dispersion patterns and ventilation parameters in a mineral processing plant.

A study was conducted in a fluorspar milling plant to assess the effectiveness of tracer gases as a reliable supplement to conventional air-monitoring and ventilation measurements. In the course of this study, a tracer gas was used as a surrogate substance to analyze the direction and the rate of spread of contaminants from various potential dust production points in the plant. Time-weighted average and continuous mineral dust concentrations were measured in several areas of the plant; these results were compared and correlated with steady-state tracer gas concentrations in the mill. Time-weighted average dust concentrations varied between 0.18 and 0.57 mg/m3 for total dust and 0.04 and 0.20 mg/m3 for quartz respirable dust, depending on the location. Correlation of these values with steady-state tracer gas concentrations yielded linear relationships with correlation coefficients (R2) of 0.95 and 0.87, respectively, for total and quartz dust. Results from this study, therefore, indicate that tracer gases may help model the spread of airborne respirable dust from point sources. These tracer gas releases also allowed the simultaneous quantitative determination of air residence times and contaminant clearance times from the building. Hence, tracer gases will help industrial hygienists obtain useful data with respect to building ventilation.     

Predicting gaseous pollutant dispersion around a workplace

Predicting the space-time evolution of a gaseous or particulate pollutant concentration in a ventilated room where a process operation is performed is imperative in hazardous activities, such as chemical or nuclear ones. This study presents a prediction of the space-time evolution of airborne pollutant dispersion following the accidental rupture of a containment enclosure (fume cupboard, glove box, pressurized gas duct, etc.). The final model is written as correlations inspired by the free turbulent jet theory, giving the space-time evolution of a pollutant concentration c (x,y,z,t) that has been formulated as a correlated function of various parameters: leak geometry (slot or round opening), emission type (continuous or transient), emission duration and initial emission velocity. These correlations are based on gas tracing experiments and on multidimensional simulations using computational fluid dynamics (CFD) tools. An instrumented experimental facility was used to simulate pressurized gas industrial failure, and the measurements performed gave the real-time evolution of a tracer gas concentration. Transient leak simulations were run in parallel with a CFD code. Comparisons between experimental and numerical results largely agree. A semiempirical model was built using a methodical parametric study of all the simulation results. This model is easy to use in safety evaluations of radioactive material containment and radiological protection inside nuclear facilities and for evaluating toxic gaseous compounds in the chemical industry.