氡气运移系数的定向测量与计算

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。     

管内向下气液两相流动界面参数分布特性

借助双探头光纤探针测量方法,对管内竖直向下空气-水两相流动的界面参数局部分布特性进行了实验研究。实验段采用内径50 mm、长度2 000 mm的圆管,气液两相表观速度范围分别为0.004～0.077 m/s和0.43～0.71 m/s。实验结果表明,不同于竖直向上两相流动中局部界面参数径向分布呈现的“壁峰”或“核峰”型分布,向下流动中局部界面参数径向分布呈“壁峰”或“宽峰”型分布;向下流动时空泡份额截面平均值均比向上流动时大119.6%～145.0%,界面面积浓度截面平均值比向上流动时大18.8%～82.5%;向下流动时界面参数分布表现出明显的均匀化趋势。     

~(237)Np在膨润土中表观扩散系数的测定

在大气和低氧条件下使用静态背对背扩散法测定了237Np在红泉膨润土中表观扩散系数Da值。实验结果如下:大气条件下237Np在混合型、Ca 型、Mg 型膨润土中的Da值分别为3 9×10-13,5 6×10-13,8 4×10-13m2/s;低氧条件下相应的Da值分别为3 4×10-13,4 7×10-13,3 1×10-13m2/s。在大气条件下以混合型膨润土为例,使用扩散池方法测得237Np的表观扩散系数Da值为8 2×10-12m2/s。     

倾斜管内上升泡状流界面参数分布特性实验研究

采用双头光纤探针对倾斜圆管内空气-水两相泡状流界面参数分布特性进行了实验研究,包括局部空泡份额、气泡通过频率、界面面积浓度及气泡当量直径径向分布特性。实验段内径为50 mm,液相表观速度为0.144 m/s,气相表观速度为0~0.054 m/s。结果表明倾斜管内向上泡状流气泡明显向上壁面聚集。局部界面浓度、空泡份额及气泡通过频率径向分布相似。倾斜条件下局部界面参数分布下壁面附近峰值相对于竖直状态被削弱甚至消失,上壁面附近峰值被加强,中间区域从下壁面往上逐渐增大,且随倾斜角度的增加变化更加剧烈。气泡等价直径随径向位置、气相速度及倾斜角度的不同无明显变化,气泡聚合和破碎现象较少发生。通过气泡受力分析解释了倾斜对泡状流局部界面参数分布的影响机理。     

氡及其子体水平扩散系数测量研究

氡气运移的研究成果表明,氡气的运移具有方向性。本文从实验入手,采用静态、累积、高灵敏度的测氡方法,对氡累积水平扩散分布进行了测量。采用最小二乘法拟合方法对不同温度条件下氡及其子体的水平扩散系数进行了计算。实验研究结果表明,氡及其子体的水平扩散系数与温度的相关系数为0.92,两者呈线性正相关关系;在恒温(30℃)条件下的实测水平扩散系数为0.049cm2·s-1;要使氡在空气中的水平扩散系数达到经典值0.1cm2·s-1,其环境温度应达到40℃以上。     

矩形通道内泡状流-弹状流转变判定准则研究

以空气和去离子水为工质,对竖直矩形通道内两相流流型特性进行实验研究;矩形通道的横截面为1.41mm×40 mm和10 mm×40 mm,实验压力为常压,气、液相表观速度分别为0.015⁰.59 m/s和0.0250.59 m/s和0.025³.74 m/s。利用获得的实验数据及文献数据,对4种典型泡状流-弹状流转变判定准则进行评价,结果表明4种准则都存在一定局限性。从实验数据及文献数据可以看出,泡状流-弹状流转变临界空泡份额为通道窄边与宽边比(宽高比s/w)的函数。为此,以当量直径10 mm为界,分别提出临界空泡份额计算关系式,从而得到修正转变判定准则。与本文及文献中实验数据的比较,修正准则较4种典型准则精度和适用性有一定提高。     

竖直圆管内泡状流界面参数分布特性

采用双头光纤探针对内径为50 mm竖直圆管内空气-水两相泡状流界面参数径向分布特性进行了实验研究。气液两相表观速度变化范围分别为0.004～0.05 m/s和0.071～0.283 m/s。结果表明,竖直管内向上泡状流局部界面面积浓度（IAC）、空泡份额及气泡频率径向分布相类似,即气相流速较低时管道中间很大范围内以上3个局部界面参数几乎恒定,近壁区迅速下降到较低值;随气相流速的增加,局部界面参数在管道中心出现峰值。本实验中气泡聚合与破碎现象较少发生,索特平均直径沿径向近似均匀分布,且随气液两相流速变化很小。通过气泡横向受力解释了局部界面参数分布的影响机理。     

腐殖酸对Re(Ⅶ)在高庙子膨润土中扩散的影响研究

腐殖酸是环境中普遍存在的一种有机物,它能通过络合作用和氧化还原反应影响放射性核素的迁移。本文通过贯穿扩散实验,在不同膨润土密度和不同腐殖酸接触时间下,研究了Re(Ⅶ)在高庙子膨润土中的扩散,得到了有效扩散系数De和容量因子α。结果显示,随着膨润土密度从1 600kg/m3增加至1 800kg/m3,De从1.8×10-11 m2/s减小至0.59×10-11 m2/s。随着腐殖酸接触时间由0d增加到60d,De由0.59×10-11 m2/s增大至0.83×10-11 m2/s。实验得到的α值均小于总孔隙率,说明在腐殖酸存在的条件下,Re(Ⅶ)可能仍以阴离子的形态在膨润土中扩散。     

氡运移实验研究与氡团簇运移机理

设计了一套可以在理想条件下观测氡气运移的装置 ,通过多次实验发现 :在理想条件下 ,虽然氡及其子体的比重比空气大 ,却具有明显向上运移能力 ,存在一种比扩散和重力沉降大得多的“上浮”运移机制。本文提出了氡团簇运移模型对这一现象进行解释 ,该模型认为 :He核及He可以与氡及其子体结合成团簇 ,由于He很轻 ,当这一团簇的重量小于空气对它的浮力时 ,导致团簇自行上升     

Zr-2.5Nb压力管材料氢致延迟开裂行为研究

研究了含氢60μg/g的Zr-2.5Nb压力管材料的氢致延迟开裂(DHC)行为,采用"力值波动监测法"来监测试样DHC裂纹扩展情况,计算了不同试验条件下试样的应力强度因子门槛值(KIH)和氢致延迟开裂速率(DHCR),同时研究了温度和轧制方向对DHC行为的影响规律。结果表明:实验温度为250℃时,Zr-2.5Nb合金DHCR范围为5.15×10~(-8)~15.14×10~(-8) m/s,KIH值范围为16.55~18.49 MPam~(1/2);实验温度为200℃时,DHCR范围为2.11×10~(-8)~2.36×10~(-8) m/s,KIH值范围为26.22~30.89 MPam~(1/2)。随着温度的降低,DHCR减小,KIH值升高。预制裂纹方向垂直于轧制方向时,DHC开裂现象不明显。     

Calculation and measurement of migration coefficient of radon under laboratory conditions

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.     

氡通过不同滤膜的扩散系数测量研究

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。     

氡及其子体运移规律与机理研究

应用高灵敏度、高精度、静态、累积、易于重复观测的CD－1α标测氡技术,在室内较理想条件下,进行了氡及其了体“自身”固有的运移规律与机理研究。实验发现：（1）氡及其子体在理想条件下的空气中,其纵向运移能力远大于横向运移能力,前者＞90％,后者＜10％;（2）氡及其子体比重很大,但其向上运移的贡献＞45％,向下运移的贡献＜45％;（3）氡及其子体和母体衰变放出的α粒子减速后之^He可与它们形成团簇,当其比重小于空气时,能自行上升。     

Characteristics of gas-liquid two-phase flow in a capillary tube

Gas-liquid two-phase phenomena in capillary tubes were investigated with special attention on the flow patterns, the time varying void fraction and pressure loss. The directions of flow were vertical upward, horizontal and vertical downward. Pipe inner diameters used were 1 mm, 2.4 mm and 4.9 mm. As a result it is made clear that due to the strong effects of surface tension the flow pattern is not severely affected by the direction of flow, the smaller the pipe inner diameter, the easier the formation of liquid slug and the pressure loss in a unit length takes much larger than the estimated value by the Chisholm equation.     

Heat flux distribution from a volumetrically heated pool with high Rayleigh number

Experimental results are presented on the heat flux distribution at the boundaries of volumetrically heated pools at high enough Rayleigh numbers to be directly relevant to the problem of retention of a molten corium pool inside the lower head of a reactor pressure vessel. The experimental facility, named COPO, is a 2-dimensional “slice”, Joule-heated and geometrically similar in shape (torispherical at 1/2-scale) to the lower head of a VVER-440 reactor. The results show that: the heat flux on the side wall (vertical portion) is essentially uniform; the downward heat flux strongly depends on position along the curved wall; and average fluxes on the side in the downward direction are in agreement with existing correlations, but somewhat underestimated in the upward direction. For the shape considered, the heat flux along the lower curved wall seems to be independent of the presence and extent of the liquid pool (contained by the vertical sidewalls) portion above it.     

ICRP Publication 115. Lung cancer risk from radon and progeny and statement on radon

Recent epidemiological studies of the association between lung cancer and exposure to radon and its decay products are reviewed. Particular emphasis is given to pooled case-control studies of residential exposures, and to cohorts of underground miners exposed to relatively low levels of radon. The residential and miner epidemiological studies provide consistent estimates of the risk of lung cancer, with significant associations observed at average annual concentrations of approximately 200 Bq/m3 and cumulative occupational levels of approximately 50 working level months (WLM), respectively. Based on recent results from combined analyses of epidemiological studies of miners, a lifetime excess absolute risk of 5 × 10?? per WLM [14 × 10?? per (mJh/m3)] should now be used as the nominal probability coefficient for radon- and radon-progeny-induced lung cancer, replacing the previous Publication 65 (ICRP, 1993) value of 2.8 × 10?? per WLM [8 × 10?? per (mJh/m3)]. Current knowledge of radon-associated risks for organs other than the lungs does not justify the selection of a detriment coefficient different from the fatality coefficient for radon-induced lung cancer. Publication 65 (ICRP, 2003) recommended that doses from radon and its progeny should be calculated using a dose conversion convention based on epidemiological data. It is now concluded that radon and its progeny should be treated in the same way as other radionuclides within the ICRP system of protection; that is, doses from radon and its progeny should be calculated using ICRP biokinetic and dosimetric models. ICRP will provide dose coefficients per unit exposure to radon and its progeny for different reference conditions of domestic and occupational exposure, with specified equilibrium factors and aerosol characteristics.     

重庆市氡浓度水平调查

对重庆市主城区环境空气、房地产建筑工程场地、伴生放射性矿堆场和宾馆室内空气氡浓度进行了调查。调查结果表明:主城区在12个区24个测点的环境空气中氡浓度年均值为10.8Bq/m3;房地产建筑工程场地土壤中的氡浓度按6个工地统计均值为1193Bq/m3;不同伴生矿的矿堆场周围空气中氡浓度水平差异很大,其中萤石矿最大,其次是铅锌矿;堆场周围空气中氡浓度水平按10类被调查的矿种统计平均值为65.2Bq/m3,萤石矿堆场周围空气中氡浓度平均值369Bq/m3,约是全市区域环境空气中氡浓度的35倍;8家宾馆109个客房室内氡浓度年均值为32.9Bq/m3。     

Se(Ⅳ)在伊利石-蒙脱石混合物中的扩散行为

采用贯穿扩散法研究了Se(Ⅳ)(代替79Se(Ⅳ))在伊利石-蒙脱石混合物中的扩散行为。结果表明,蒙脱石的伊利石化对Se(Ⅳ)的迁移行为有明显影响,Se(Ⅳ)的有效扩散系数De从3.89×10-11 m2/s增加至18.1×10-11 m2/s。伊利石-蒙脱石混合物比例为1∶9~5∶5时,De的变化不明显,伊利石-蒙脱石混合物比例为6∶4时,De明显增大,表明矿物的优势组分对Se(Ⅳ)的扩散行为起主导作用。随着伊利石-蒙脱石混合物比例从1∶9增大至6∶4,Se(Ⅳ)的岩石容量因子由4.07降低至0.75,分配系数由22.7×10-4 m3/kg降低至1.95×10-4 m3/kg,它们均随伊利石含量的增加而降低,这表明由于伊利石对Se(Ⅳ)的吸附能力较蒙脱石弱,导致伊利石-蒙脱石混合物对Se(Ⅳ)的阻滞能力变弱,从而增大了Se(Ⅳ)的迁移能力。