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治理铀废石堆的主要手段为砌拦渣墙、土壤覆盖并植树等,但是对于不同性质土壤、季节(温度、湿度)变化条件下的防护效果没有进行系统的研究。本文对铀废石堆覆盖不同物理性质(颗粒密度、孔隙比、含水率等)土壤,在不同环境条件下,测量其表面的氡析出率。结果发现,氡在土壤中的扩散系数随着土壤粒径增大而增大,随着含水率的增加而减小。 相似文献
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基于气体透过滤膜的扩散原理,对应用于固体核径迹探测器累积测氡的三种滤膜在四种不同湿度下的氡扩散能力进行研究。实验结果表明:醋酸纤维滤膜和普通滤纸的扩散能力明显强于PE滤膜,更适用于固体核径迹测氡,且湿度对三种滤膜氡扩散能力的影响不明显。通过本次实验得到,醋酸纤维滤膜的扩散系数为1.46×10~(-9)m~2/s~2.59×10~(-9)m~2/s,普通滤纸的扩散系数为1.01×10~(-9)m~2/s~1.45×10~(-9)m~2/s。 相似文献
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本文通过氡浓度和氡子体α潜能积累方程,从理论上研究了铀矿井中氡子体浓度与氡浓度和矿井通风的关系。指出了回风流中氡子体浓度与氡浓度比值的大小,主要取决于通风换气的时间和入风流污染的程度。 相似文献
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通风降氡是铀矿辐射防护的主要内容之一。根据我国铀矿通风技术的发展,以及通风与氡析出规律研究的不断深入,将我国铀矿通风技术发展划分为5个阶段:1958—1965年期间通风降氡技术学习建立阶段,主要为学习引进前苏联的压入式通风方式;1966—1977年期间技术发展平台阶段,体现在以抽出式通风代替压入式通风的应用验证与经验积累;1978—1989年期间理论与技术发展阶段,提出了氡析出渗流-扩散规律与通风方式的相互作用理论,推动了铀矿通风防护技术的发展;1990—2002年期间停滞阶段,以减少通风防护投入来降低生产成本为目的,使铀矿通风防护技术研究处于停滞;2003—2016年期间强化发展阶段,以氡析出渗流-扩散规律指导不同采矿方法下的通风防护技术研究与应用。目前,中国铀矿通风正在向形成具有中国特色的通风降氡技术体系发展。 相似文献
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氡气运移系数的定向测量与计算 总被引:1,自引:0,他引:1
设计了一套在理想条件下的氡气定向运移实验装置,采用定向测量的方法,对氡气在垂直方向和水平方向的运移进行了测量与计算。结果表明,在水平方向上的运移系数为0.024cm2·s–1,远小于文献给出的氡气在空气中的扩散系数0.1cm2·s–1;垂直向下方向的运移系数为0.182cm2·s–1,明显大于文献给出的氡气在空气中的扩散系数。 相似文献
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LE Ren-Chang WANG Xiao-Oin 《核技术(英文版)》2006,17(2):92-96
Under laboratory conditions (i.e. a sealed system in which the temperature may vary according to air temperature), the migration of radon in upward, downward and horizontal directions has been investigated. After a period of accumulation, the spatial distribution profile of radon was drawn on the basis of the experimental data. The profile showed whorl-shape with bigger ends. The longer the accumulation time, the bigger the whorl end, and the higher the radon concentration is. By fitting the experimental data by least-square statistical method, we find that the distributions of radon follow negative exponential functions in the upward, downward and horizontal directions. However, exponents for the three directions are not exactly identical. The upward migration is more effective than the downward one and both upward and downward migrations are more effective than the horizontal one. 相似文献
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B. J. Thamer 《Journal of Nuclear Materials》1984,120(2-3):166-173
A means of measuring the diffusion coefficient of radon in a porous medium has been developed and demonstrated. It is applicable whether or not the medium has a distributed radon source. Radon exhalation is measured from a pair of parallel, planar surfaces as a function of time after the sample has been externally impregnated with radon and, if a distributed source is present, after the sample has developed its own radon. The exhalation has been measured by means of grab samples taken with small, flow-through scintillation cells. The method is free of approximations within the limits of the model. The model includes the porosity of the medium, the adsorption of radon on the solid matrix, and the radon absorption on any pore moisture. 相似文献
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针对目前氡室测控系统存在的问题,本文提出了基于CMOSense技术的SHT75数字式温湿度传感器和LaWindows/CVI虚拟仪器开发环境的设计思想。运用虚拟仪器本身提供的库函数、数据库技术和模块化的设计思想开发了氡室测控系统。该系统很好地完成了氡室里重要参数的实时全程控制,并且具有显示直观、反应迅速,性价比高等特点,因此具有一定的使用价值。 相似文献
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介绍了氧室数据采集系统的结构组成框图,数据采集系统的USB通信接口的设计方法,包括USB件电路设计、固件设计及驱动程序设计。采用USB通信具有传输速度快、开发较简单的特点。 相似文献
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Sooyoung Choi Kord S. Smith Hanjoo Kim Taewoo Tak 《Journal of Nuclear Science and Technology》2017,54(6):705-715
This paper presents consistent and rigorous accuracy assessments of various methods for calculating the diffusion coefficients in a two-step reactor core analysis of light water reactors (LWRs). The diffusion coefficients are significantly affected by the transport correction and critical spectrum calculations. There are various methods for the transport corrections (inflow/outflow/hybrid corrections) and critical spectrum calculations (B1/P1/CASMO-4E methods) so that it is necessary to decide the best combination to achieve a high accuracy in the transport/diffusion two-step analysis. Numerical tests are performed step-by-step to search for the best combination of the methods by comparing each other the transport one-step results, transport/diffusion two-step results, and Monte Carlo results. Numerical test results with a large and a small LWR core show that the combination of inflow transport correction and CASMO-4E critical spectrum calculation is most accurate than the other combinations in terms of eigenvalues and assembly power distributions. 相似文献
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《Fusion Engineering and Design》2014,89(7-8):1392-1396
Deuterium diffusion coefficient measurements of CVD-SiC were carried out using a solubility and diffusivity measurement apparatus to investigate the permeation mechanism of the hydrogen isotope through CVD-SiC. Experiments were conducted with thin-sheet-type samples with thicknesses of 0.1 mm, 1 mm, and 2 mm at 1073–1183 K. Total amount of occluded gas into or released gas from different thickness but same weight sample were expected to be the same, but unexpectedly differed by more than 50%. As the release rates after sufficient time had passed were almost the same, and the 1-mm-thick sample had twice the surface area of the 2-mm-thick sample, the measurements were probably affected by adsorbed gas on the surface. The value of D/L2 (the diffusion coefficient divided by the square of the thickness), obtained by fitting to the theoretical formula but ignoring the early phase of discharge, was in good agreement for samples of different thickness at the same temperature, and was more than 5 orders of magnitude smaller than that obtained from the permeability measurement experiments. Therefore, we believe that the deuterium permeation through CVD-SiC is primarily dependent on the permeation rate through the grain boundaries. 相似文献
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基于ICRP 66号报告中的呼吸道生物动力学模型,采用MATLAB软件中的Simulink仿真工具,建立了人体呼吸道的廓清模型,利用建立的廓清模型计算了不同参数条件下肺部有效剂量转换系数(mSv/WLM)的变化规律。结果显示吸入氡子体粒径对肺部有效剂量转换系数的影响最大,当粒径在0.7~10 000 nm之间变化时,肺部有效剂量转换系数的变化能达到10倍以上;其次是呼吸率,呼吸率直接决定了吸入氡子体粒子的数量,当成年男性重度工作状态时肺部有效剂量转换系数是睡眠状态下的4.2倍;未结合态份额对剂量转换系数的影响会随着吸入氡子体粒径值不同而发生改变,当未结合态份额从0变化到0.08时,肺部有效剂量转换系数最多能增大79%;相比而言吸收入血速率对肺部有效剂量转换系数的影响只有不到4%。 相似文献