同位素稀释质谱法测定U_3O_8中的痕量钍

报道了用同位素稀释质谱法测定U_3O_8中的痕量钍。用萃取色层法分离钍。同位素丰度质谱测定精密度为±0.1％。化学处理与质谱测定钍的流程空白值为9×10~(-9)g,方法检测限达到5×10~(-9)g,对于10~(-6)量级痕量钍的U_3O_8样品,测定结果相对标准误差为±3.5％。     

萃取色层分离—水平式ICP-AES法测定U_3O_8中25种杂质元素

本文叙述了用TBP萃取色层法分离后,用水平式ICP-AES法测定U_3O_8中25种杂质元素的分析方法。U_3O_8样品转化为硝酸铀酰后,采用以TBP萃淋树脂为固定相、5mol/LHNO_3为流动相的萃取色层法使杂质元素与铀基体分离,杂质流出液用水平式ICP为激发光源的发射光谱分析法直接测定。取样0.3g,所有元素的测定下限在0.04—5ppm之间。方法的重加回收率在82—121％之间。相对标准偏差在±13％以内。     

同位素稀释质谱法测定U_3O_8中的痕量钍

报道了用同位素稀释质谱法测定U_3O_8中的痕量钍。用萃取色层法分离钍。同位素丰度质谱测定精密度为±0.1％。化学处理与质谱测定钍的流程空白值为9×10~(-9)g,方法检测限达到5×10~(-9)g,对于10~(-6)量级痕量钍的U_3O_8样品,测定结果相对标准误差为±3.5％。     

用整体测量装置探讨胃肠道摄入难溶性浓缩铀U_3O_8时的消失动态

难溶性浓缩铀U_3O_8经口进入到胃肠道时,或经吸入在呼吸道中沉积时,大部分由于呼吸道纤毛运动而转移到胃肠道中去。虽然U_3O_8经胃肠道的吸收率极微,但浓缩铀U_3O_8进入胃肠道后,将直接引起对胃肠道的辐照和化学毒物损伤。因此,我们设计用大白鼠整体测量装置来探讨胃肠道摄入难溶性浓缩铀U_3O_8时的消失动态过程,以期为评价浓缩铀U_3O_8对机体胃肠道的危害提供依据。     

U_3O_8中微量Co的分光光度测定

本方法为分光光度法测定U_3O_8中的微量Co。Co与4—[(5—氯—2—吡啶)偶氮—1,3—二胺基苯在pH 6.1的HAc—NaAc缓冲介质中显色,所生成的络合物在2.4 N HNO_3溶液中567mμ处有最大吸收。加大显色剂用量并以酒石酸铵为掩蔽剂,可不经分离,直接用分光光度法测定U_3O_8中微量Co。当存在10mgU时,0—2.5μgCo/ml服从比耳定律。用本法分析U_3O_8标准样品,精密度为±1%,误差小于3%。     

U_3O_8氢还原制备UO_2技术研究

研制建立了卧式搅拌床系统,开展了U_3O_8氢还原制备UO_2及UO_2后续反应性研究,研究结果表明:部分来自国外的U_3O_8反应活性高;并研制建立了U_3O_8流化床试验系统,对上述条件下的U_3O_8流化质量进行了考察,结果表明U_3O_8具有良好的流态化性能。     

萃取色层分离-水平式ICP/AES法测定U_3O_8中Hf,Zr,Sc,Th,Ag

本章叙述了用萃取色层分离-水平式ICP/AES法测定U_3O_8中Hf,Zr,Sc,Th,Ag等杂质元素。U_3O_8样品用HNO_3-HF混合酸溶解,并用HCl转化成氯化铀酰后,通过以CL-TBP萃淋树脂为固定相,5mol/l HCl为流动相的萃取色层柱,将杂质元素与铀分离后,以水平式ICP为激发光源,在W-100型平面光栅摄谱仪上进行光谱测定。取样0.3g时,测定下限Hf,Zr,Th为0.23×10~(-6),Sc为0.023×10~(-6),Ag为0.04×10~(-6),重加回收率在84%～114%范围内,相对标准偏差低于10%。     

铈掺杂诱导U3O8晶型变化

铈是核反应的重要裂变元素,其氧化物CeO_2容易与UO_2燃料形成U_(1-x)Ce_xO_2固溶体。铀铈固溶体会因为U4+发生氧化而生成(U_(1-x)Ce_x)3O_(8-δ)混合氧化物。Ce在U_3O_8中的存在会改变U_3O_8母体的局域结构,影响着(U_(1-x)Ce_x)3O_(8-δ)产物的物理化学性质。研究铀铈混合氧化物的局域结构,可以帮助理解处于苛刻环境中乏燃料的性状。使用共沉淀方法制备了铈掺杂的U_3O_8混合氧化物样品,即(U_(1-y)Ce_y)3O_(8-δ)(y=0,0.05,0.20),利用粉末X射线衍射(X-ray Diffraction,XRD)获取其物相信息,借助同步辐射X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)技术来获取(U_(1-y)Ce_y)3O_(8-δ)中铀和铈的局域结构。结果表明:与掺杂前的U_3O_8具有C2mm空间群不同,掺入Ce后的(U_(1-y)Ce_y)3O_(8-δ)转变成了与U_3O_8的P62m空间群一样的晶型,Ce的存在还导致铀的平均价态升高,层内最近邻Ce-U(Ce)的原子距离减小。     

火花源质谱法定量测定UF_6中微量杂质元素

本文采用火花源质谱同时分析UF_6中Ta、Nb、Sb、W、Mo、V、Sr、Pb、Bi、Zn、Th十一个微量元素。UF_6样品水解后,加入内标Y、Lu,同位素稀释剂和浓硫酸。溶液蒸乾后,残渣在马弗炉中850℃下灼烧20 min,使转化成U_3O_8。用高纯银粉与U_3O_8混合(重量比为1:1)。压成电极后,用火花源双聚焦质谱仪进行分析。采用内标法和同位素稀释法达到了定量分析目的。内标法的相对标准偏差为±13—40%。同位素稀释法的相对标准偏差为≤±13%。分析结果与其它分析方法测定值相符。测定灵敏度除Th(5ppm)外均达1ppm以下。     

U_3O_8粉末硅藻土、硬铝、不锈钢、金属铜和镍中杂质含量的全分析

U_3O_8粉末硅藻土、硬铝、不锈钢、金属铜和镍中杂质含量的全分析@王兴尧@赵敦忠$中国建筑材料科学研究院!北京@李泽@吴杰@罗上庚@刘大鸣     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

Interaction between uranium and humic acid (Ⅰ): Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) ＞SHA (HA from the surface) ＞THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g)ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5 - 6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Information for authors

<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumen-     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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