工业用铱-192γ照相源的制备

一、铱-192γ照相源的制备在工业无损探伤工作中,γ射线探伤设备具有体积小、重量轻、携带方便、不依赖于外部能源、工作效率高等优点,适合于施工现场作业。近年来,γ射线探伤技术在高压容器和管路焊接,喷气式发动机维修保养等工作中获得越来越广泛的应用。放射性核素铱-192的γ射线能量适中,可用于厚度为6—100 mm范围内的钢铁材料无损探伤。铱-192是由铱-191在原子反应堆经中子照射而生成的。自然界的铱元素中含     

用放射性示踪技术研究海洋沉积物中铱的吸附和解吸行为及其富集机制

利用放射性示踪技术,结合静态吸附、解吸实验及可见分光光度分析,研究了海洋沉积物－海水体系中铱的吸附及解吸行为。结果表明,在极低的铱浓度范围内,铱的吸附－解吸等温线呈线性,咀吸附－解吸不可逆。IrCl6%2-形态的铱极易被沉积物所吸附,一旦吸附后又难解吸焉。沉积物沉积过程中不断地吸附海水中的IrCl6^2-,可能致使铱累积于沉积物中,从而引起铱富集,丹麦鱼粘土对铱的吸附能力弱于近海洋沉积物,说明丹麦鱼粘土高含量铱来源于其它成因控制,如火山或地外成因。     

铱-192工业探伤源对典型居民区的剂量计算

根据中国原子能科学研究院铱- 192工业探伤源物理参数,采用蒙特卡罗方法程序(MCNP)计算了铱-192源在典型居民区的空间剂量分布和居民的吸收剂量率.结果表明:水平方向1200 cm处在“有”和“无”混凝土墙防护情况下的吸收剂量率分别为12.2000和2090.0000μGy/h,垂直方向吸收剂量率随位置呈指数衰减;铱-192源所存放2#居民楼3楼层以上住户的吸收剂量率低于USNRC限值.计算结果将为铱- 192放射源事故的评估和受照人群的医学治疗提供参考.     

阴离子交换预浓集-中子活化法测定近岸海水样品中的超痕量铱

利用放射性192 Ir示踪技术及近紫外 -可见吸收光谱分析 ,研究了阴离子交换树脂对海水中铱的吸附行为 ,建立了天然海水样品中铱的阴离子交换预浓集流程 ,回收率达 90 %。在超净条件下 ,采用此流程结合中子活化分析测得黄海近岸海水样品中的铱浓度为 2 .6× 10 - 14 g/mL。     

西藏仲巴地区白垩系-第三系(C-T)界线的中子活化研究

用中子活化法研究了取自西藏仲巴地区白垩系-第三系界线的一套岩石样品,初步实验结果表明,界线粘土层显示有高浓度的铱,本文从铱的浓度分布、在界面附近碳酸钙的含量变化以及稀土元素的丰度模式等方面,探讨了界线事件的原因,其中地外物质撞击是有吸引力的一个机制。     

白令海和北冰洋海水中铱的阴离子交换预富集-中子活化分析

研究了用阴离子交换预富集 中子活化法测定海水中铱的分析方法。192Ir示踪实验结果表明,在0 05～1 2mol/LHCl介质中,酸度越低越有利于树脂对Ir的吸附;阴离子交换法对pH=1 5的酸化海水中痕量Ir的回收率为89%;聚乙烯瓶和pH=1 5的酸化条件可以长期保存海水中的Ir。在超净实验条件下,用阴离子交换预富集 中子活化法测定了白令海和北冰洋垂直剖面样品中Ir的浓度,结果分别为(0 85～3 58)×10-12g/L(白令海,采集深度为0～3504m)和(1 26～1 97)×10-12g/L(北冰洋,采集深度为25～1900m),试剂空白值为(0 18～0 20)×10-12g/L。     

利用AG1-X8树脂放射化学中子活化法测定若干地质标准参考物中的Ir

利用192Ir放射性示踪研究了铱在AG1－X8阴离子树脂上的吸附解吸行为。首先用氯气对样品溶液中铱的化学种态进行调整，然后对吸附在树脂上的铱用抗坏血酸还原，最后用HClO4与HCl混合液洗脱，实验结果表明，全流程对铱的回收率高于92％，利用建立的流程测定了丹麦地质标准参考物FC－1，结果与推荐值吻合，测定了3个日本地质标准参考物JSd-1,JLk-1和JMn-1，铱的含量分别为0．10，0．03，1．70ng.g^-1。     

通古斯卡爆炸现场泥炭样品的中子活化研究

用中子活化法研究了取自１９０８年通古斯卡爆炸现场一个钻孔泥炭样品中的铱和其它有关元素的丰度变化,发现在１９０８年爆炸层及其上覆层位处的铱有明显的异常,最大铱丰度约为背景值的５倍以上。     

微堆中子活化法测定硒鸡蛋中硒含量

利用核反应７６＾Ｓｅ（ｎ，γ）＾７７Ｓｅ＾ｍ，热中子活化法，在微型反应堆上测定不同浓度硒饲料喂养的鸡所生蛋的蛋黄、蛋清和蛋皮中硒含量。结果表明：饲料中加入硒越多则鸡蛋中硒浓度越高，硒鸡蛋各组份中蛋黄含硒量最高，蛋清最低。     

铱-192在运输过程中发生辐射泄漏

2001年12月27日,在将铱-192从瑞典经法国往美国的运输过程中发生辐射泄漏。这3国的主管部门表示,没有任何人受到辐射达到2 rem (20 mSv)的剂量,目前还不清楚货包是从何处开始泄漏的。但有关官员表示辐射泄漏最可能发生在铱-192运抵到达美国后。 在共分为7级的国际核事件分级表(INES)中,这次事故被暂定为3级。这是自INES于1991年开始得到应用以来,瑞典主管部门定为级别最高的一次事故。目前3国的主管部门正在对此次事故进行详细调查。 铱-192在运输过程中发生辐射泄漏     

Analysis of dinosaur samples by nuclear microscopy

Several dinosaur bone and eggshell fossil samples unearthed at different sites in China were analyzed by means of nuclear microscopy. Concentrations and distributions of elements such as Na, Mg, Al, P, S, Ca, Cr, Mn, Fe, Cu, Zn, As, Br, Sr, Y, Ce, Pb and U, etc. were obtained for each sample. The results of quantitative PIXE and RBS analyses show unusually high concentrations of U and Ce in several samples obtained from a period near the K-T boundary (between Cretaceous and Tertiary periods, 65 million years ago), suggesting that some form of environmental pollution could be the cause of dinosaur extinction.     

Distribution of Fission Products in Irradiated UO2

Inhomogeneities of fission products and plutonium distribution in irradiated UO₂ were examined. UO₂ pellets were ground so as to let them fracture along the grain boundaries, and the fragments were then dissolved successively into several fractions. The specific activities of these fractions were compared, and the distribution of fission products in the grain and grain boundaries were studied. It was found that at lower temperatures of irradiation (～1,400°C), the fission products, except Cs, were distributed fairly uniformly over the grain, while Cs had accumulated at the grain boundaries. At higher temperatures (near or above the melting point of UO₂), inhomogeneity was noticed in the Zr-Nb and Cs distribution. The concentration of these elements varied along the temperature gradient of the fuel rod than within the grains. Zr-Nb was found to be concentrated in the higher temperature areas of the fuel rod, while conversely, the concentration of Cs was smaller in the same areas. Distribution of Ce, Ru and Pu was found to be fairly uniform throughout the grains. The process of fission product migration in UO₂ is also discussed in the paper.     

用超热中子活化法测定大鼠肝脏亚细胞组分中的砷

采用差速离心分离技术与超热中子活化分析法 (ENAA) ,测定了大鼠肝脏亚细胞组分 (细胞核、线粒体、溶酶体、微粒体、胞液 )中As的质量分数 ,并对标准参考物质作对照分析。分析结果表明 :As在各亚细胞组分中并非均匀分布。As在微粒体中的质量分数最高 ,在细胞核中最低。用t检验比较了在中毒组大鼠和正常组大鼠肝脏中各亚细胞组分中As含量的差别 ,以及中毒组大鼠肝亚细胞组分之间的差异。发现上述两组肝亚细胞组分中As存在极显著性差异 (P <0 0 0 1)。在中毒组肝亚细胞组分中 ,微粒体中As的含量与胞液无显著性差异 (P >0 0 5 ) ,但与细胞核、线粒体、溶酶体存在明显的差异 (P <0 0 5 )。     

Combustion of stratified hydrogen-air mixtures in the 10.7 m combustion test facility cylinder

This paper presents preliminary results from hydrogen concentration gradient combustion experiments in a 10.7 m³ cylinder. These gradients, also referred to as stratified mixtures, were formed from dry mixtures of hydrogen and air at atmospheric temperature. Combustion pressures, burn fractions and flame speeds in concentration gradients were compared with combustion of well-mixed gases containing equivalent amounts of hydrogen. The studied variables included the quantity of hydrogen in the vessel, the steepness of the concentration gradient, the igniter location, and the initial concentration of hydrogen at the bottom of the vessel.Gradients of hydrogen and air with average concentrations of hydrogen below the downward propagation limit produced significantly greater combustion pressures when ignited at the top of the vessel than well-mixed gases with the same quantity of hydrogen. This was the result of considerably higher burn fractions in the gradients than in the well-mixed gas tests. Above the downward propagation limit, gradients of hydrogen ignited at the top of the vessel produced nearly the same combustion pressures as under well-mixed conditions; both gradients and well-mixed gases had high burn fractions. Much higher flame speeds were observed in the gradients than the well-mixed gases.Gradients and well-mixed gases containing up to 14% hydrogen ignited at the bottom of the vessel produced nearly the same combustion pressures. Above 14%, hydrogen, gradients produced lower combustion pressures than well-mixed gases having the same quantity of hydrogen. This can be attributed to lower burn fractions of fuel from the gradients compared with well-mixed gases with similar quantities of hydrogen. When ignited at the bottom of the vessel, 90%, of a gradient's gases remained unburned until several seconds after ignition. The remaining gases were then consumed at a very fast rate.     

动态膜电解制备四价铀Ⅰ.装置建立及性能测试

以钛涂钌铱网为阳极、钛网为阴极,建立了动态膜电解制备四价铀装置,测试了该装置的性能,比较了使用国产膜和进口膜时的电解性能,同时还探讨了制备过程中各参数的变化。研究结果表明:该装置能在电流密度高达120mA/cm2的情况下稳定运行;隔膜采用贝斯特Nepem-417膜或旭化成Aciplex-F4112膜,对电解结果无显著差异;对于500mL铀质量浓度为199g/L的料液,仅采用72cm2的钛涂钌铱网为阳极、钛网作为阴极,电解180min,四价铀产率可达到93.1%;电解前后阴极料液中肼浓度从0.52mol/L下降为0.30mol/L,酸浓度从2.20mol/L下降为0.70mol/L,槽压在3～3.6V内变动,阴极电解液温度低于45℃(室温28℃)。