Modified "DMC" technique for stretching DNA molecules

A modified “dynamic molecular combing”(DMC) technique used for stretching double-stranded DNA is reported.DNA molecules were stretched on the silanized mica surface by this technhique,its speed being precisely controlled with a computer,This approach combined the precise DNA stretching method with high resolution AFM imaging at nanometer scale,thus making it useful for DNA alignment manipulation and subsequent gene research.     

起草《辐射防护规定》中的某些考虑

本文介绍在结合我国具体情况尽量采用ICRP和IAEA等国际权威组织的有关建议及先进国家的标准的原则下,制定我国《辐射防护规定》中考虑和研究的一些问题。其中主要是:辐射防护最优化原则在辐射防护规定中如何具体化;加强和明确对可能造成天然辐射水平增高的实践的限制的必要性;确定公众成员年有效剂量当量限值和婴儿、儿童的ALI的依据;明确和强调流出物监测的意义;对流出物排放的控制,要将过去单纯的浓度控制改变为既控制浓度又控制总量;明确辐射防护评价的基本要求、主要内容和上报评价报告规定的必要性;对辐射工作人员的医学监督必须根据一般职业医学原则进行等。还介绍了与这些问题有关的近期的一些研究进展。     

先进压水堆"C"形环研究

"C"形环是一种用于压力容器法兰密封的密封环,目前国内使用的为进口"C"形环.为了研制出性能良好的国产"C"形环,本课题对试制的"C"形环密封性能进行了深入研究,并在"C"形环的制造工艺上取得了突破.研制的样环通过了冷热态综合性能试验,结果表明其研制的工艺合理,试制的"C"形环密封性能良好.此项研究结果为研制工程用"C"形环打下了基础.     

用于ADS启明星1#中子涨落特性测量的微电流放大器研制

通过对次临界反应堆中子噪声特性的分析,设计了一种能反映ADS系统启明星1#实验装置中子涨落特性的微电流放大器。通过设计和调试,该放大器能够实现10^-9－10^-11A的电流－电压通频带转换放大,达到了设计的要求。     

点击化学在18F标记PET药物中的应用

“点击化学”是一种模块化的合成方法,在生物偶联、药物筛选、材料科学等领域得到了广泛的应用,而其中的Cu（I）催化的叠氮与炔的1,3-偶极环加成（CuAAC）反应,由于其在温和条件下高效快速的反应特点,几乎成了“点击化学”的代名词。它一经引入到PET氟［¹⁸F］药物标记中就获得了极大的成功,受到了越来越多的放射性药物工作者的关注。本文重点根据Click合成子的分类综述了点击化学在¹⁸F标记分子探针中的应用,也对近两年应用到¹⁸F标记中的环张力促进的点击标记进行了介绍,并简要展望了这些应用的发展前景。     

Waveguide ultrasonic liquid level transducer for nuclear power plant steam generator

This paper deals with the development and utilization of a new acoustic method to control the level of the coolant in industrial power-generating equipment. The development research was carried out on the basis of the method of acoustic impedance, based on measuring attenuation of a longitudinal ultrasonic wave in a waveguide sensing element. Ultrasonic attenuation is determined by the degree of submergence of the sensing element in liquid. For this purpose waveguide ultrasonic transducers are used, made with specially designed technology (waveguide acoustic transducers—WAT-technology). The transducers are adapted for operation under extreme conditions in the water coolant with temperatures up to 350°C and pressure up to 20 MPa. The paper tackles: principle of operation of transducers, methods of testing under laboratory conditions, design and results of calibration in a thermophysical test facility, results of the operational trial of the level transducer at the nuclear power plant in Zaporozhye.     

分析设计应力分类方法的"一次最小结构"法研究

提出了一种有效的应力分类方法——“一次最小结构”法。该方法基于应力线性化技术及弹性有限元应力计算方法。在评定过程中,一次总体薄膜应力和一次弯曲应力在“一次最小结构”中加以校核,其它应力都在原结构中加以评定。通过解除原结构中“不利约束”的影响,该方法得到了更为接近极限载荷的一次应力评定结果。本文给出了应用“一次最小结构”法进行应力分类与评定的实例,并将计算结果与不采用应力线性化方法以及目前标准中给出的分析方法的计算结果进行了比较。结果表明,应用该方法能得到更大的许用载荷计算值,从而获得更为接近于极限载荷的应力评定结果。     

“Chen”型沸腾传热计算方法用于小通道传热计算的适应性

目前,计算沸腾传热最为常用的Chen公式和基于Chen公式的计算方法在用于小通道时计算误差较大。运用Yan和Lin等人的实验结果,建立了一个包含11种工质,当量直径在0.21～6.05mm区间,由2505个实验数据组成的数据库,对Chen公式和"Chen"型计算方法用于小通道传热计算的适用性进行了评价。对比分析结果表明:Chen方法和"Chen"型计算方法误差较大,Chen公式中核态沸腾传热系数的计算方法在高含气率区已经不再适用。     

“一带一路”沿线国家铀资源合作开发展望

按照世界核协会预测,2025年之后,全球对天然铀需求将保持较快增长,但天然铀产量却无法保持同步增长,从而导致缺口出现。按照我国核电建设规划来看,2030年将达到1.5亿~2.0亿kW,每年大约需要2.2万t天然铀。如何在做好国内铀矿勘查,提高天然铀产能的同时,加快海外国家尤其是"一带一路"沿线国家的铀资源开发力度,实现"两个市场,两种资源"并举,对保证我国核电发展和实现核工业"走出去"战略都具有重要意义。在对"一带一路"国家铀资源分布状况和开发条件研究基础上,提出了开展海外铀资源开发工作建议。     

半球形CdZnTe伽马谱仪在放射性"热点"测量中的应用

核设施退役过程中,对退役场所进行"热点"调查(包括"热点"定位,活度测量等)是非常重要的.为了配合伽马相机在热点调查后对"热点"进行更为精确的测量,建立了一套配有铅屏蔽准直器的CdZnTe伽马能谱系统,用Visual c#语言编写了便于现场操作的谱分析软件MiniAnalysis,对现场用CdZnTe谱仪测得的能谱进行...     

Determination of more realistic Ke,r-factors for simplified elastic–plastic analysis

According to the relevant KTA-Rules, e.g. KTA 3201.2 (KTA, 1994), strain correction factors—K_e-factors—have to be used in the fatigue analysis of pressurised components if the strain intensity ranges are determined by elastic analyses, and if in this case the range of primary plus secondary stress intensity exceeds a certain limit. This limit is three times the design stress intensity value, S_m, and thus approximately corresponds to twice the value of the 0.2% strain limit. The relations given in the above-mentioned rules to determine the K_e-factors for considering plastification have proved to be very conservative in many cases compared with the strain intensity ranges that were determined by complete elastic–plastic analyses. In order to improve the validity of the fatigue analysis, the topic of `Performance of fundamental work to prepare concrete proposals for realistic K_e,r-factors (strain correction factors) to consider plastification at large strain amplitudes' was one of the subjects of the BMU project SR 2063. Work on this topic was jointly performed by GRS and Siemens. In summary, the result was that the proposed realistic K_e,r-factors present a real alternative to the K_e-factors of the regulations; the latter serve a mostly conservative registration of the observed elastic–plastic strain but cannot be explained in terms of physics and are not formulated in a manner adequately specific of any material. The exemplary verification calculations that have been performed so far show, furthermore, that the proposed realistic K_e,r-factors can be easily determined and also deliver sufficiently conservative results. This new method therefore has great potential which, however, still has to continue to be verified by further calculations before it can be included in the KTA-Rules.     

简析《AP1000核电厂严重事故管理导则》的框架结构

在严重事故下,核电厂状态千变万化,如何缓解事故是对核电厂人员的极大挑战.《AP1000核电厂严重事故管理导则》指导技术支持中心评估事故状态,分析缓解措施的正反两面影响,确定最佳缓解策略,由主控室操纵员进行实施并监视其有效性.本文对《AP1000核电厂严重事故管理导则》的框架结构进行了梳理,以便核电厂工作人员更好地理解和使用这一导则.     

The design of “multiple energies from one source” in D-T neutron tube

To obtain multiple monoenergetic neutron sources and realize the on-site calibration of radiation monitoring equipment for nuclear-involved places,the structural characteristics and neutron source features of D-T neutron tube were analyzed;Monte Carlo method was adopted to simulate the effect of interaction between typical materials and different energy neutrons;multilayered shielding materials were combined and optimized to acquire the optimal scheme to shield the neutron sources from the neutron tube.On the base,a tapered alignment filtration construction was designed and Monte Carlo method was employed to simulate the effect of alignment construction.The result showed that the tapered alignment filtration construction can create monoenergetic neutrons including14.1 MeV,0.18 MeV and thermal neutrons and demonstrated good monochrome performance which provides multiple monoenergetic sources for the on-site calibration.     

薄层色谱“一条”法检测~(99)Tc~m药物的放化纯度

临床注射99Tcm-MDP后,需等待2～3 h,至本底下降时才能进行骨显像。因怀疑系99Tcm-MDP的放化纯度偏低所致,于2002年试用上行薄层色谱"一条"法测定其放化纯度。该法的固定相为硅胶条,流动相为V(10%醋酸铵)∶V(甲醇)=1∶1,展开、干燥后进行放射性自显影。2008年用免洗胶片代替传统X光胶片进行自显影,检查99Tcm-MDP、99TcmO4-、99Tcm-EC、99Tcm-DTPA、99Tcm-MIBI和99Tcm-MAA6种药物"一条"法的分离效果,由自显影图像测得99Tcm-MDP的Rf为0.7,并定性估测其放化纯度高于2002年。2009年用同法测定99Tcm-DTPA、99Tcm-MIBI和99Tcm-MDP的放化纯度,前两种的自显影图像与2008年结果相同,其Rf分别为0.78±0.02和0.39±0.03。99Tcm-MDP的检测结果与2008年的相差较大,其Rf接近于零,这可能是由于99Tcm-MDP是一种具有锝锡胶体特性的复合物,其标记用药盒在贮存有效期(52周)内氯化亚锡含量下降而导致Rf的显著变化,该变化用两条法(一条测游离锝,另一条测锝锡胶体)难以测出。因此,建议生产厂家继续研究一种可用于测定多种锝药物的TLC,如将组分分离完全后,利用放射性曲线峰面积计算放化纯度或锝标记率,实现锝药物测定方法的规范化。     

软X射线功率谱仪测量系统在"强光一号"的丝阵实验

闪烁体和光电管组成的软X射线功率谱测量系统,在西北核技术研究所的"强光一号"加速器上,测量得到了各种丝阵靶的X射线辐射功率波形,并对测量结果进行了分析.     

Development of very-high-density low-enriched-uranium fuels

Following a hiatus of several years and following its successful development and qualification of 4.8 g U cm⁻³ U₃Si₂–Al dispersion fuel for application with low-enriched uranium in research and test reactors, the US Reduced Enrichment for Research and Test Reactors program has embarked on the development of even-higher-density fuels. Our goal is to achieve uranium densities of 8–9 g cm⁻³ in aluminum-based dispersion fuels. Achieving this goal will require the use of high-density, γ-stabilized uranium alloy powders in conjunction with the most-advanced fuel fabrication techniques. Key issues being addressed are the reaction of the fuel alloys with aluminum and the irradiation behavior of the fuel alloys and any reaction products. Test irradiations of candidate fuels in very-small (micro) plates are scheduled to begin in the Advanced Test Reactor during June, 1997. Initial results are expected to be available in early 1998. We are performing out-of-reactor studies on the phase structure of the candidate alloys on diffusion of the matrix material into the aluminum. In addition, we are modifying our current dispersion fuel irradiation behavior model to accommodate the new fuels. Several international partners are participating in various phases of this work.     

Data requirements for neutron activation: Part I: Cross sections

Existing neutron cross section libraries such as EAF-2003 contain a large number of reactions. Of these only a small proportion are significant in the production of the nuclides that dominate activation quantities such as activity or γ-dose rate at various decay times. These reactions were identified in a recent extensive set of calculations on all the elements and reported in the ‘Activation Handbook’. These 1340 reactions are considered here and the set of reactions with no differential or integral data are listed and prioritised. A set of 339 reactions with very limited possibility of measurement are given; these require further study by theoretical calculations. A set of 100 reactions with either discrepant or no data, that might be measurable are listed and are recommended to be the subject of future experimental work.     

Banquet Speech "Man's Conquest of Energy, Its Ecological and Human Consequences"

The world's energy resources suitable for power production are of two classes: (1) various channels of the continuous energy flux from extraterrestrial sources, and from the earth's interior, and (2) chemical, thermal, and nuclear energy stored in the outer part of the lithosphere and in the oceans. The continuous energy influxes are from: solar radiation, 178,000 × 1012 watts; geothermal energy, 32 × 1012 watts; and tidal energy, 3 × 1012 watts. Of the solar energy influx, the only fraction suitable at present for large-scale power production is the approximately 40,000 × 1012 watts expended in evaporation of water and in atmospheric and oceanic circulation. Of this, the world's potential water power is about 2.9 × 1012 watts. A very small fraction of the solar influx, 40 × 1012 watts, is stored chemically by photosynthesis. A minute fraction of this, stored during the geologic past, is the source of the energy of the fossil fuels, coal and petroleum. Tidal power is capable of large-scale development in a small number of coastal localities with a total potential power of about 64,000 megawatts. Of the sources of stored energy, geothermal energy is the least important. Installed capacity by 1970 is about 1,125 electrical megawatts, and the ultimate potential is estimated at about 60,000 megawatts, with a lifetime of probably less than a century. The largest sources of stored energy, other than nuclear, are the fossil fuels. The initial minable world reserves of coal and lignite are estimated to have been about 7.     

Part-through cracks in pipes under cyclic bending

The propagation of a circumferential external surface crack in a metallic round pipe under cyclic bending loading is examined through a two-parameter theoretical model. A finite element analysis is carried out to determine the stress-intensity factor distribution along the front of the flaw, which is assumed to present an elliptical-arc shape with aspect ratio α=a_el/b_el (a_el, b_el=ellipse semi-axes). The relative depth ξ of the deepest point on the front is equal to the ratio between the maximum crack depth, a, and the pipe wall thickness, t. The parameter R/t, with R=internal radius of the pipe, is made to vary from 1 to 10. The fatigue growth of the surface flaw occurs according to preferred paths in the diagram of α against ξ.