洞庭湖水系铀的水环境背景值研究

区域水环境背景值研究是水环境质量评价的基础,也是研究元素分布、分配和迁移转化规律的基础性工作。水中铀背景值研究不仅可了解放射性水平而且具有水法普查铀矿的实际意义。本工作采用裂变径迹分析技术对247000km~2的洞庭湖水系一百余处断面的河水、水库水 和泉水等原水和过滤水中的含铀量进行了测定,对数据做了计算机统计处理,得出了洞庭湖水系和湘资远澧各流域的区域铀水环境背景值,并与国内外情况做了比较。此外,还讨论了水中铀的季节性变化,流域内水库、泉和自然保护区的铀水平。     

洞庭湖水系铀的水环境背景值研究

区域水环境背景值研究是水环境质量评价的基础,也是研究元素分布、分配和迁移转化规律的基础性工作。水中铀背景值研究不仅可了解放射性水平而且具有水法普查铀矿的实际意义。本工作采用裂变径迹分析技术对247000km~2的洞庭湖水系一百余处断面的河水、水库水和泉水等原水和过滤水中的含铀量进行了测定,对数据做了计算机统计处理,得出了洞庭湖水系和湘资沅澧各流域的区域铀水环境背景值,并与国内外情况做了比较。此外,还讨论了水中铀的季节性变化,流域内水库、泉和自然保护区的铀水平。     

湘江流域大气降水中痕量铀的裂变径迹法测定

大气降水是地表水和地下水的重要来源,因此与人类生活有着密切的关系。近些年来人们对大气降水的酸度引起了普遍关注,并对其形成和危害等方面做了探讨。对降水中一些阴、阳离子浓度及其变化进行了观测,但对降水中天然放射性铀的测定尚不多见。本文利用裂变径迹法测定了湘江流域部分地区以及北京市中关村某些降水中的含铀量.初步探讨了大气降水中铀的可能来源及其差异的原因。     

湘江衡阳段天然放射性核素水平调查

为了掌握湘江衡阳段天然放射性核素水平及来源,分别于枯水期(11—12月)、丰水期(4—6月),对湘江衡阳段和该段4条主要支流(舂陵水、蒸水、耒水、洣水)水中的U、Th、²²⁶Ra、⁴⁰K、²¹⁰Po、²¹⁰Pb 6种天然放射性元素/核素进行了调查。测量结果表明:与长江水系及洞庭湖水系历年放射性水平均值相比,湘江衡阳段6种天然放射性核素中²²⁶Ra、²¹⁰Po、²¹⁰Pb明显偏高,说明湘江衡阳段的确受到了放射性污染。4条支流中,舂陵水及蒸水放射性核素浓度异常,明显高于汇入前后的湘江水体的放射性活度浓度。因此,这两条支流区域可能存在放射性污染源头,应对这两条支流区域进行更深入的取样调查,找出其污染源。     

湖南省水体中天然放射性核素浓度调查研究

本文报道了湖南省江河、湖泊、水库、泉、井和自来水中的天然放射性核素浓度的调查结果。全省共设采样点165个,共采集平、枯水期水样330个。调查结果表明,湖南省水体中天然放射性核素浓度属正常本底水平;四大水系中湘江水系的天然放射性水平最高,沅江和澧水水系最低;湖泊和水库水中天然放射性水平与江河水相近。     

某铀矿山和水冶厂生活区辐射剂量的初步估算

前言我们所观测的某铀厂矿是已投产十年的铀矿山和水冶厂的联合企业。对矿井下和水冶厂各车间的放射性水平已经积累了不少数据,但对附近生活区人员的辐射剂量水平情况仍不够清楚。为了了解这方面的情况,自1977年起在过去历年常规监测的基础上,扩大了监测项目和范围,先后对厂矿附近生活区的地表γ照射量率、表面放射性沾染、空气中放射性气溶胶、氡浓度及其子体α潜能值,以及土壤、水和食品中放射性水平进行了调查研究,并对生     

中国铀矿床同位素地球化学特征(英文)

中国铀矿床大多产于地槽褶皱带和活化区地质背景中,以热液铀矿床占主导地位。铀矿床的成矿时代集中于中生代末、新生代初,即白垩-第三纪时期,在时间和空间分布上具有相对集中的特点。根据铀-铅同位素体系演化原理论证了铀的活化成矿观点;根据地质体中铀的丢失和异常初始铅判别铀源及评价成矿远景。轻稳定同位素地球化学研究,表明成矿溶液中硫、碳同位素组成与含矿岩石的性质有关,“就地取材”特征表现非常明显;氢、氧同位素地球化学表明中国热液脉型铀矿的成矿溶液来源有三种情况,即岩浆热液和大气降水相混合,主要来源于大气降水及变质水和大气水相混合。     

广西北部摩天岭地区铀成矿特征浅析

摩天岭地区铀成矿与岩体风化剥蚀、大气降水、储矿构造闭合性及特定的还原环境密切相关;岩体表层风化剥蚀物和变质岩残留体为铀成矿提供铀源,表层浸取作用使铀从铀源体中浸出,并随大气降水沿构造进入地下,硅质热液活动将成矿流体加热并上升到近地表成矿.从铀源、水源、热源、储矿构造及还原环境等方面对其成矿特征进行了简单叙述,并建立了铀成矿模式.     

飞来峡水库坝区环境放射性水平调查

对飞来峡水利枢纽工程前后(1997～2000年)飞来峡水库库区水环境和坝区环境放射性水平进行了调查,测量了水环境介质(包括水、沉积物、水草、鱼、虾等)的放射性水平、大坝及周围居民区环境氡和土壤的放射性水平、飞来峡水利枢纽建设管理局辖区内的两个采石场的7辐射剂量率水平。调查结果表明：飞来峡水库库区水体中天然放射性核素^238U、^226Ra、^232Th浓度在水利枢纽工程前后无明显变化;水库水底沉积物主要是沙,其放射性水平低于库区土壤和岸边泥土;飞来峡水利枢纽工程坝区的环境放射性水平与未施工前比,总体保持在原来的水平;坝区属于放射性水平偏高地区,但不影响居民的居住。     

河北省水体中天然放射性核素浓度调查研究

本文报道了河北省河流、湖泊、水库、海水、泉水、农村井水以及城镇自来水中天然放射性核素浓度的调查结果。全省167个采样点的198个样品的调查结果表明,河北省各类水体中除个别点的个别核素浓度较高外,属正常本底水平。     

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。     

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)

正~~     

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.