利用CE1-GRS数据分析月表钍元素分布特征

为了从嫦娥一号伽玛射线谱仪(CE1-GRS)探测数据获取月表元素的分布特征,提出并实现了一种对CE1-GRS 2C级数据进行处理的方法。采用该方法对CE1-GRS第一正飞期2C级数据产品进行分析处理,得到了Th元素计数率的全月分布图。与月球勘探者伽玛射线谱仪(LP-GRS)数据的Th全月分布图进行比较分析,结果表明,两者体现出的月表Th分布主要特征基本一致,但分布细节特征存在一些差异。     

嫦娥一号宇生伽马射线能谱分析

介绍了一种通过宇生伽马射线分析月表部分元素含量的方法。我国嫦娥一号卫星携带的伽马射线能谱仪(CE1-GRS)探测的伽马射线能谱中,既包含月表天然放射性元素(K、U、Th等)放出的伽马射线,也包含银河宇宙射线(GCR)与月表物质(Fe、Si、O等)发生簇射反应过程中产生的伽马射线。根据已知GCR的强度和能量分布,使用蒙特卡罗方法模拟,计算出GCR与月表物质反应产生的伽马射线特征峰及面积,并与CE1-GRS测量谱线相比较,建立了几种元素测量谱线与其月表含量的关系,该方法将可用于月表非天然放射性元素平均含量的计算。     

嫦娥一号和嫦娥二号月球γ能谱解析

为了从嫦娥系列绕月γ能谱测量实验获取月表γ能谱特征,应用CE1-GRS和CE2-GRSγ能谱2C级科学数据,首先从散射本底扣除后的谱线中提取出弱特征峰信息,然后对嫦娥系列仪器谱进行定性分析,推定月表存在的可能元素种类。结果表明:(1)从CE1-GRSγ能谱能识别U、Th、K、Fe、Mg、Si、Al和O等8种月表可能元素,从CE2-GRSγ能谱能识别U、Th、K、Fe、Mg、Si、Al、O、Ti和Ca等10种月表可能元素;(2)卫星绕行轨道距月表距离越近、探测器的能量分辨率越高,得到的月球轨道γ能谱将更精细,从而能获取更准确的月表元素种类及其分布特征。     

基于奇异值分解方法的嫦娥一号γ射线谱仪谱线定性分析

针对嫦娥一号γ射线谱仪(CE1-GRS)探测数据难以从谱形特征直接进行定性分析的问题,提出采用噪声调整的奇异值分解(NASVD)方法提取CE1-GRS数据中相互正交的谱线主成分,然后分别分析月表各区域对应谱线的低序层谱线中的峰信号,通过鉴别各峰信号对应的能量值是否等于特定元素的特征γ射线能量来确定月表各区域的元素种类。结果表明,该方法能够识别出的月表可能元素包括U、Th、K、Fe、Ti、Si、O、Al、Mg、Ca和Na等11种元素。     

NASVD方法在CE1-GRS谱线分析中的应用研究

直接从谱形特征上对嫦娥一号伽玛射线谱仪(CE1-GRS)的3级谱线数据进行分析,难以确定月表元素的种类。提出采用噪声调整的奇异值分解(NASVD)方法对CE1-GRS谱线进行定性分析。分析结果表明,该方法能够识别出的月表可能元素包括U、Th、K、Fe、Ti、Si、O、Al、Mg和Ca等10种元素,也能够通过各观测谱线对应于第一主成分的幅度绝对值大小反映对应月表区域的总放射性活度强弱。     

4～400 MeV宇宙线质子对近月空间轨道γ能谱中湮灭辐射的贡献

为进一步明确月球表面湮灭辐射的主要来源和影响机理，构建了轨道γ能谱仪中湮灭辐射特征峰定量分析模型，采用GEANT4模拟不同能量质子轰击月岩诱发γ射线微分能谱，并以“嫦娥一号”高能粒子探测器(Chang’e-1 High-energy Particle Detector,CE1-HPD)数据作为输入项，计算了宇宙射线中4～400 MeV质子在月表5种典型岩石中诱发湮灭辐射的特征峰信息。在对“嫦娥一号”γ能谱仪(Chang’e-1 Gamma-ray Spectrometer,CE1-GRS)获取的0.511 MeV特征峰进行本底扣除和天然放射性核素影响剥离后，与4～400 MeV质子诱发湮灭辐射结果进行比较。研究结果表明：级联簇射产生湮灭辐射的概率与入射质子能量呈正相关，在4～400 MeV能量范围内，典型月岩的成分差异对诱发湮灭辐射的影响不明显。虽然该能量段质子的注量率较高，但由于其能量较低，无法有效地通过级联簇射形成正电子，最终导致湮灭辐射贡献率较低，仅为(1.97±0.66)×10^-4。     

绕月探测中伽玛能谱分析初步进展

探测月表元素的含量与分布对于月球科学的探索与研究具有深远的意义,通过"嫦娥一号"绕月探测卫星数据,我们绘制了铀、钍、钾等元素相对计数的全月分布图,间接反映了元素的含量及分布。对比分析阿波罗和月球勘测者绕月卫星数据,发现了结果中一些相同和差异点。     

月表岩石诱发γ辐射场原始谱特征模拟

玄武岩、克里普岩、橄榄岩在月球表面广泛分布,并具有一定的代表性,并且岩石密度差异较大,高能粒子(Galactic Cosmic Rays,GCR;Solar Particle Event,SPE)与岩石相互作用后激发γ射线。利用蒙特卡罗软件FLUKA开展了月表高能质子诱发γ射线的研究,获取了月表多种成岩主元素的特征γ射线能量峰、正电子湮灭峰和γ辐射平衡峰等原始谱特征信息。通过数据分析表明特征峰强度与月表岩石密度呈正相关。原始谱特征的研究不仅可以为不同系列绕月γ数据的对比研究提供参考,也可为在全月表面进行基于核辐射方法的岩石密度填图研究提供理论支撑。     

面向行星表面元素测量的小型化伽马谱仪原理样机设计

对行星表面物质受宇宙射线激发或天然衰变而产生的伽马射线进行探测,是一种测量行星表面主要元素成分及其空间分布的可靠技术手段,已被多个行星探测任务采用。提出了将CZT探测器与SiPM读出闪烁晶体相结合的行星元素伽马谱仪方案,该方案兼具低能段的高能量分辨率和高能段的高探测效率,同时可以减小来自非探测方向伽马背景的影响,且具有较小的体积、重量和功耗。为进行初步的技术路线验证,设计了一个将CZT阵列(单个灵敏尺寸1 cm×1 cm×0.5 cm)与BGO探测器(晶体的主体尺寸8.4 cm×8.4 cm×4 cm)相结合的小型化伽马谱仪原理样机,并开展了物理模拟。完成了前端探测器模块、数据处理模块和FPGA控制逻辑的设计实现,以及原理样机的组装。使用放射源、上海光源激光伽马光束线和中子激发伽马对谱仪进行了测试,CZT探测器对¹³⁷Cs@662 keV伽马射线的能量分辨率(FWHM)为2.1%,可以较好地分辨低能伽马射线,BGO晶体能够较好地探测和分辨高能伽马射线。该方案为未来小型化行星伽马谱仪的工程设计提供了参考。     

微计算机在我国多道谱仪系统中的应用

多道谱仪主要指γ能谱分析系统,X射线谱仪和穆斯堡尔谱仪等,这些系统已在许多领域中得到广泛的应用。它们的共同特点是:(1)实验数据自动获取;(2)实时显示或准实时显示;(3)实验数据在线处理或联线处理;(4)自动打印或描图,并能直接得到实验报告。     

Effects of water chemistry and potential distribution on electrochemical corrosion potential measurements in 553 K pure water

The effects of water chemistry distribution on the potential of a reference electrode and of the potential distribution on the measured potential should be known qualitatively to obtain accurate electrochemical corrosion potential (ECP) data in BWRs. First, the effects of oxygen on a platinum reference electrode were studied in 553 K pure water containing dissolved hydrogen (DH) concentration of 26–105 μg kg^?1 (ppb). The platinum electrode worked in the same way as the theoretical hydrogen electrode under the condition that the molar ratio of DH to dissolved oxygen (DO) was more than 10 and that DO was less than 100 ppb. Second, the effects of potential distribution on the measured potential were studied by using the ECP measurement part without platinum deposition on the surfaces connected to another ECP measurement part with platinum deposition on the surfaces in 553 K pure water containing 100–130 ppb of DH or 100–130 ppb of DH plus 400 ppb of hydrogen peroxide. Measured potentials for each ECP measurement part were in good agreement with literature data for each surface condition. The lead wire connecting point did not affect the measured potential. Potential should be measured at the nearest point from the reference electrode in which case it will be not affected by either the potential distribution or the connection point of the lead wire in pure water.     

ATHLET程序的钠冷快堆应用扩展及其验证

系统分析程序是对钠冷快堆的冷却剂回路系统进行全局模拟、瞬态及事故安全分析的重要工具。本工作对德国核设施与反应堆安全机构（GRS）开发的轻水堆最佳估算系统程序ATHLET进行修改,增加了钠的物性公式和传热关系式,将其适用范围扩展到钠冷快堆。为验证修改过的ATHLET程序,对法国凤凰（Phenix）反应堆系统建模,并对其自然对流实验进行模拟,将计算结果与实验数据进行比较。结果显示,ATHLET程序的钠冷快堆应用扩展具有良好的适用性。     

秦山核电厂高压安注系统可靠性分析

文章用故障树分析方法对秦山核电厂高压安注系统的可靠性进行了分析。这项工作是采用西德反应堆安全研究所(GRS)研制的RALLY程序包进行的,内容包括系统不可用度计算、不确定度分析、统计评估以及重要度分析。有关分析结果为寻找秦山厂高压安注系统的薄弱环节、改进系统设计提供了参考依据。     

Modeling of condensation in horizontal tubes

Condensation in horizontal tubes plays an important role for example in the determination of the operation mode of horizontal steam generators of VVER reactors or passive safety systems for the next generation of nuclear power plants. Two different approaches (HOTKON and KONWAR) for modeling this process have been undertaken by Forschungszentrum Jülich (FZJ) and the University for Applied Sciences Zittau/Görlitz (HTWS) and implemented into the 1D-thermohydraulic code ATHLET, which is developed by Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH for the analysis of anticipated and abnormal transients in light water reactors. Although the improvements of the condensation models are developed for different applications between generators and emergency (VVER steam generators-emergency condenser of the SWR1000) with very different operation conditions (e.g. the temperature difference over the tube wall in HORUS is up to 30 K and in NOKO up to 250 K, and the heat flux density in HORUS is up to 40 kW/m² while that in NOKO is up to 1 GW/m²) both models are now compared and assessed by Forschungszentrum Rossendorf FZR e.V. Therefore post-test calculations of four selected HORUS experiments were performed with ATHLET/KONWAR. It can be seen that the calculations with the extension KONWAR as well as HOTKON significantly improve the agreement between computational and experimental data.     

Radiation imaging using a compact Compton camera inside the Fukushima Daiichi Nuclear Power Station building

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown in the aftermath of a large tsunami caused by the Great East Japan Earthquake of 11 March 2011. The measurement of radiation distribution inside the FDNPS buildings is indispensable to execute decommissioning tasks in the reactor buildings. We conducted a radiation imaging experiment inside the turbine building of Unit 3 of the FDNPS by using a compact Compton camera and succeeded in visualizing high-dose contamination (up to 3.5 mSv/h). In addition, we drew a three-dimensional radiation distribution map inside the turbine building by integrating the radiation image resulting from the Compton camera into the point cloud data of the experimental environment acquired using a scanning LRF. The radiation distribution map shows the positions of these contaminations on a real space image of the turbine building. The radiation distribution map helps workers to easily recognize radioactive contamination and to decrease their own exposure to radiation because the contamination cannot be observed with the naked eye.