Droplets behaviors of flashing jet in accidental release of superheated liquid

Structural failure of an industrial superheated liquid tank or pipe usually results in the flashing jet consisting of a mixture of massive droplets and vapor due to the violent phase transition. In this work, experiments on small-scale releases were carried out with a 20 L storage tank to investigate the droplets behaviors of flashing jets after accidental releases of superheated liquid. Distribution of droplets axial, radial and vertical velocities, as well as droplets diameter along the centreline of flashing jet, were acquired employing a Phase Doppler Anemometry (PDA). The influence of storage pressure, superheat, and nozzle diameter was also studied. Results show that the distribution of actual droplets with different velocities and diameters follows the normal distribution. Droplets mean three-dimensional velocities on the central axis of flashing jet decrease exponentially with the increase of axial distance. The droplets mean diameter first decreases exponentially and finally keeps sable at about 10 μm. Among three-dimensional velocities, the axial velocity is the highest and the vertical velocity is the lowest. Droplets mean three-dimensional velocities increase with the increase of storage pressure, superheat, and nozzle diameter. The droplets mean diameter decreases with the increase of superheat and nozzle diameter but increases with the increase of storage pressure.     

Hazard analysis on LPG fireball of road tanker BLEVE based on CFD simulation

In order to research the hydrocarbon fireball characteristic of LPG tanker Boiled Liquid Evaporate Vapor Explosion (BLEVE) under different conditions, computational fluid dynamics (CFD) simulations of the hydrocarbon fireballs from the LPG tanker BLEVE accidents were carried out. Several new different factors, such as the mass of fuel, inlet velocity and airflow velocity, were considered to analyze the influence on the evolution of the characteristics of the fireball and the development of the LPG tanker BLEVE accidents. Results indicate that the fireball with a greater mass of fuel radiates more heat but slower. The large longitudinal diameter of the fireball and high radiation heat flux are observed in case of a faster inlet velocity used for the same mass. The airflow was found to shorten the initial phase of the fireball effectively. Some suggestions were proposed to prevent the LPG BLEVE accidents. Analysis performed show that various parameters like fireball diameter, radiative heat flux and lifting speed of fireball can be predicted well using FDS code.     

A study of the atmospheric dispersion of a high release of krypton-85 above a complex coastal terrain, comparison with the predictions of Gaussian models (Briggs, Doury, ADMS4)

Atmospheric releases of krypton-85, from the nuclear fuel reprocessing plant at the AREVA NC facility at La Hague (France), were used to test Gaussian models of dispersion. In 2001-2002, the French Institute for Radiological Protection and Nuclear Safety (IRSN) studied the atmospheric dispersion of 15 releases, using krypton-85 as a tracer for plumes emitted from two 100-m-high stacks. Krypton-85 is a chemically inert radionuclide. Krypton-85 air concentration measurements were performed on the ground in the downwind direction, at distances between 0.36 and 3.3 km from the release, by neutral or slightly unstable atmospheric conditions. The standard deviation for the horizontal dispersion of the plume and the Atmospheric Transfer Coefficient (ATC) were determined from these measurements. The experimental results were compared with calculations using first generation (Doury, Briggs) and second generation (ADMS 4.0) Gaussian models. The ADMS 4.0 model was used in two configurations; one takes account of the effect of the built-up area, and the other the effect of the roughness of the surface on the plume dispersion. Only the Briggs model correctly reproduced the measured values for the width of the plume, whereas the ADMS 4.0 model overestimated it and the Doury model underestimated it. The agreement of the models with measured values of the ATC varied according to distance from the release point. For distances less than 2 km from the release point, the ADMS 4.0 model achieved the best agreement between model and measurement; beyond this distance, the best agreement was achieved by the Briggs and Doury models.     

Assessing deposition levels of 55Fe, 60Co and 63Ni in the Ignalina NPP environment

Two RBMK-1500 reactor units operated in Lithuania in the 1987-2004 period (one of them was stopped for decommissioning in 2004). This study presents a preliminary investigation of surface deposition density levels of ⁵⁵Fe and ⁶³Ni in moss samples collected in the close vicinity of the Ignalina NPP. Non-destructive analysis by the HPGe gamma-spectrometry was followed by radiochemical separation. Radiochemical analysis was based on anion-exchange and extraction chromatography. ⁵⁵Fe and ⁶³Ni activities were measured by liquid scintillation counting (LSC). The results indicate that the deposition values of ⁵⁵Fe are generally higher than those of ⁶⁰Co and ⁶³Ni.     

高压管道天然气泄漏扩散过程的数值模拟

采用CFD模型的方法对高压管道内的天然气泄漏和扩散过程进行了数值模拟。其结果表明,从高压管道泄出的天然气在大气中主要表现为高速射流的泄漏过程和随后的扩散过程。在泄漏过程中,天然气在泄漏口附近为欠膨胀射流,整个泄漏过程具有一定的高度;在扩散过程中,天然气在浮力作用下以向上扩散的形式发展。研究了不同环境风速对扩散过程的影响,较大的风速可以使天然气向下风方向更远的距离扩散,从而增大了天然气爆炸危险浓度的范围。研究结果可     

液液萃取-高效液相色谱法同时测定水中甲萘威和阿特拉津

用二氯甲烷萃取水中的甲萘威和阿特拉津,经旋转蒸发和氮吹富集浓缩后,采用高效液相色谱二极管阵列检测器在222 nm波长下测定。甲萘威和阿特拉津在0.100 mg/L～5.00 mg/L范围内线性良好,检出限分别为0.031 μg/L和0.027 μg/L,空白水样加标平均回收率为78.5%～91.7%,平行测定3次的RSD＜5%。     

液液萃取-气相色谱法测定饮用水中硝基苯类化合物

采用液液萃取－气相色谱法测定饮用水中10种硝基苯类化合物,通过萃取条件优化试验,选择正己烷为萃取剂,使目标物在0μg／L～38.5μg／L之间线性良好,检出限为0.002μg／L ～0．005μg／L。实际饮用水样的加标回收率为80.8％～104％,RSD＜3％。用该方法测定桂林市4个水厂饮用水,结果硝基苯、间－二硝基苯、2,4－二硝基氯苯未检出,其余7种硝基苯类化合物虽有检出,但检出值均低于标准规定的限值。     

液液萃取-气相色谱-质谱法同时测定饮用水中的酞酸酯、百菌清和联苯胺

建立了液液萃取-气相色谱-质谱（LLE -GC/MS）同时测定饮用水中的6种酞酸酯类化合物、百菌清和联苯胺的方法。选用3种有机溶剂进行萃取,筛选出回收率高、操作简单的前处理方法,萃取后经气相色谱-质谱分析。方法表明：8种物质线性良好,相关系数为0．9978～0．9995,用二氯甲烷萃取回收率最佳,回收率在90．1％～118％之间,相对标准偏差在0．24％～7．21％之间。     

加速溶剂萃取-液相色谱测定土壤中酞酸酯类化合物

建立了加速溶剂萃取-液相色谱法测定土壤中14种酞酸酯类化合物的方法。结果表明,该方法对14种酞酸酯分离度较好,加标回收率为67.1%~128%,精密度RSD(n=6)为5.2%~15.0%,方法检出限为0.021~0.034 mg/kg。该方法操作简便、准确,具有较好的实用性。     

固相萃取-液相色谱/质谱法测定水中硝基苯酚类化合物

建立了固相萃取-液相色谱/质谱测定水中硝基苯酚类化合物的方法。在最优条件下,7种硝基苯酚类化合物的分离度较好,目标物在0.02~3.00 mg/L范围内线性良好,相关系数均0.998,检出限为0.007~0.026μg/L,加标回收率为71.1%~95.9%,精密度为7.36%~18.6%。该方法操作简便、准确,具有较好的实用性。