10^6量级^252Cf自发裂变中子源用屏蔽操作柜设计

描述了106量级252Cf自发裂变中子源用屏蔽操作柜的研制情况.介绍了该屏蔽操作柜的设计原则、设计考虑、屏蔽计算和屏蔽材料的选择.并用小强度源实际测量屏蔽操作柜性能.研制的屏蔽操作柜材料从外到内为不锈钢外壳(2mm)、聚乙烯(150mm)、不锈钢内壁(20mm).在操作者操作位置处中子屏蔽达到9倍,γ屏蔽达到近3倍.结果表明该屏蔽操作柜能满足操作人员实际操作需要和所受剂量限值要求.     

60Co辐照装置剂量场均匀性的优化设计

采用蒙特卡罗方法和MATLAB(Matrix Laboratory)程序对由576根钴源构成的辐照装置中剂量场均匀性进行优化设计.首先将程序计算结果与实验测量进行比较,接着对程序设置3200个计算点计算了辐照装置的剂量场分布;剂量场均匀性计算中,不断地改变钴源棒位置并不断计算空间平面剂量场.计算结果发现,程序计算值与实验测量值较为一致,经调整后装置的空间剂量均匀度显著提高,使得辐照装置的能量使用率大大提高.     

用蒙特卡罗方法确定81-02型198Au短程治疗源剂量计算参数

针对81-02型¹⁹⁸Au短程治疗源的临床应用，用蒙特卡罗方法计算了在一半径为30cm的理论球体模型中，AAPMTG43U1所推荐剂量计算参数的数值，包括剂量率常数、径向剂量函数和各向异性函数。所得单个81-02型¹⁹⁸Au短程治疗源的剂量率常数为1.113 cGy·h^-1·U^-1，与Dauffy等的理论计算值和TLD实测值分别相差0.18%和1.62％。在源中垂轴0.1～10.0cm距离范围内计算径向剂量函数的数值，在角度0°～90°（10°间隔）、距离0.5～9.0cm（1cm间隔）范围内计算各向异性函数的数值，最后对径向剂量函数和各向异性函数进行拟合，得到实用性较强的经验公式。     

复合型种子源~(125)I-~(103)Pd剂量场分布的蒙特卡罗模拟与实验测定

在相同参数条件下,使用MCNP5、EGSnrc两种蒙特卡罗方法模拟和实验测定~(125)Ⅰ-~(103)Pd复合种子源剂量场分布情况,实验中采用LiF热释光剂量片(GR-200)记录吸收剂量,有机玻璃为组织等效材料。通过与实验结果比较,两种程序在模拟粒子输运方法、几何描述、材料截面数据等方面结果不同,但是两种程序计算结果与实验符合较好。结果表明,MCNP5和EGSnrc可准确计算种子源剂量场分布。EGSnrc得到的剂量数据更加准确。     

点通量计算方法在人体内放射治疗剂量场计算中的应用

TPS(治疗计划系统)是内放射治疗的一个关键环节,通过精确的剂量场计算来优化种子源的数目和种植位置,使得靶区(病灶区域)获得尽可能均匀的有效剂量分布,同时最大限度减少正常组织和要害器官的受量。TPS中剂量场计算通常是将特定的包含靶区的计算区域分成若干微小的几何单元(离散化),然后利用蒙特卡罗方法计算每个单元中的沉积能量,进而最终转化成吸收剂量。但是当考虑计算靶区内某个点的吸收剂量时,直接计算该点的沉积能量非常困难,我们采用了蒙特卡罗方法计算该点的点通量,进一步求得该点的吸收剂量。我们计算了125I种子源在水中的剂量…     

国产改进型不锈钢的辐照损伤随辐照温度变化研究

不锈钢常用作散裂中子源的靶结构材料。散裂中子源系统是ADS系统中的重要组成部分之一，为驱动次临界装置提供源中子。在ADS散裂中子源系统中，不锈钢(S．S．)用于束窗及靶材料，材料将受到高能、高强度的质子或／与中子辐照，年积累位移损伤剂量可达几百dpa。不锈钢的辐照损伤与辐照温度及剂量有关。     

大动物模型内的中子剂量分布

计算了在圆柱形狗模型中的中子剂量分布;假定模型主要由 H、C、N 和 O 四种元素组成,单能中子平行束是沿与柱轴垂直方向入射在模型表面上。计算中考虑了弹性散射、非弹性散射、俘获反应和非散射过程。以随机步长跟踪每个入射中子,直至中子的能量小于0.3eV 或者中子跑出该系统为止。低能中子的 N(n,p)C 和 H(n,γ)D 反应的剂量贡献是根据扩散理论处理的。本文给出了单能中子和感生γ射线的剂量-深度分布。计算是用 NPDC 程序——中子在生物组织中的输运程序完成的。     

油砂地层井眼水源距对中子-伽玛能谱影响的模拟

介绍了中子-伽玛能谱测井中研究中子-伽玛射线随空间、能量、时间分布的蒙特卡罗(Monte Carlo)模拟软件包.在裸眼井、井眼里无下井仪器、油饱和砂岩地层、井眼注淡水等条件下,用该软件包计算了井轴和井壁的不同源距(和垂距)地层中子-伽玛射线随能量、时间的分布,以及井轴和井壁在各种源距下的中子-伽玛射线能谱,亦即研究了源距变化对中子-伽玛射线随能量、时间分布以及井轴与井壁中子-伽玛射线能谱的影响.     

基于三维输运方法的压水堆主冷却剂~(16)N源项计算分析

在反应堆功率运行期间,一回路冷却剂水中的~(16)O受高能中子照射,活化生成~(16)N。~(16)N衰变会释放出高能γ射线,是反应堆内冷却剂系统放射性的主要来源。对一回路冷却剂中~(16)N源项进行计算可为反应堆屏蔽设计提供依据。~(16)N活度浓度及其在一回路中的分布是安全审评中的关键参数。为了精确计算~(16)N源项,本文首先使用JSNT程序计算了堆芯及其相邻区域的高能快中子注量率分布,然后考虑冷却剂在反应堆压力容器内的流动和照射情况,以及其在一回路中的流动和衰变情况,编制了~(16)N源项计算程序,在计算过程中考虑了快中子注量率的三维分布。以某三代压水堆核电厂为例计算了~(16)N源项在一回路中的分布。计算结果表明,使用三维中子注量率分布可以得到更精细的~(16)N源项分布;上下腔室内中子注量率对一回路中~(16)N源项分布影响很小,可以不予考虑。     

0Cr18Ni10Ti不锈钢源壳TIG焊接温度场数值模拟及试验验证

针对0Cr18Ni10Ti不锈钢放射源源壳钨极氩弧焊(TIG)焊接过程,采用ANSYS有限元软件对焊接温度场进行数值模拟分析,建立了非稳态TIG焊接熔池形态的数值分析模型,分析中引入了热焓和表面分布高斯电弧热源模型,初步计算了焊接电流和焊接速度对焊接温度场分布的影响。通过比较焊缝有效熔深的测量结果和计算结果,验证了所建模型的正确性和可靠性。以计算结果为基础,对焊接工艺参数进行优化,建立了0Cr18Ni10Ti不锈钢放射源源壳的焊接工艺路线。     

Stresses and strains in the steel containment resulting from transient pressure and temperature loading during loss-of-coolant accident

Posttest calculations of stresses and strains in the steel containment of the German research reactor HDR were performed for a simulated LOCA. The results of the theoretical investigations will be presented and compared to experimental findings. The pressure and temperature loading of the shell was determined with the thermodynamic code COFLOW on the basis of a multi-compartment model. Using a three-dimensional finite element model the temporal behaviour of the containment was calculated employing the structural mechanics code ASKA. Global bending deformations and local negative straining of the steel shell is discussed. Theoretical and experimental results agree in most cases rather well. Reasons for deviations will be discussed. The specific behaviour of strains found in the vicinity of locally heated areas will be explained by means of analytical considerations.     

面向强放热室退役的高效复合去污技术研究

强放热室作为反应堆材料辐照检验的配套设施,其辐射水平高、结构复杂、去污难度较大。针对强放热室退役不锈钢壳体去污的特殊性和复杂性,开展了高压水射流去污、可剥离膜去污和机械打磨去污3个单项去污试验和去污工艺试验研究,并创新性的提出了一种强放热室不锈钢壳体高效复合去污工艺。经工程去污实践验证,去污后热室不锈钢覆面表面污染水平均低于40 Bq/cm2,去污因子最高达110以上,达到了国内先进水平。热室高效复合去污技术的研发解决了强放热室不锈钢壳体表面去污的技术难题,降低了退役阶段工作人员的受照剂量,保护了工作人员和环境的安全,具有显著的经济、社会效益。      

17-4PH不锈钢纳米析出物的磁小角中子散射研究

本文充分发挥中子对磁灵敏、穿透力强等技术优势,利用加载磁场小角中子散射实验技术研究核电站实际服役14年的阀杆17 4PH不锈钢样品。结果表明,与不加磁场时相比,加载磁场条件下二维散射图谱呈明显各向异性,在散射矢量垂直于磁场方向上散射强度显著增强。利用多分散球模型对数据进行拟合,结合原子探针实验结果分析得出,衬度的增加降低了Cu析出物周围元素分布不均匀对散射的相对贡献,从而有助于更加准确地获得Cu纳米析出物的尺寸。     

宏观-微观模型和朗之万方法在低能核裂变研究中的应用

基于三维朗之万模型对低能核裂变动力学过程和断点构型进行了研究,其中位能曲面采用基于双中心壳模型和有限程液滴模型的宏观 微观模型计算得到,质量张量和黏滞张量分别采用Werner Wheeler方法和墙加窗一体模型得到。以14 MeV中子诱发235U裂变为例,分别研究了拉长形变空间和壳衰减因子对裂变碎片质量分布、总动能分布及断点处核拉长与质量非对称度关联的影响,确定了模型计算中拉长形变空间边界至少应为35R0（R0为球形核半径）,以及壳衰减因子的合理取值为60 MeV。基于该模型,计算得到了14 MeV中子诱发233,235U裂变碎片质量分布,与ENDF/B Ⅷ0评价数据符合较好,说明该模型具有定量计算裂变碎片质量分布的能力。     

Material properties for reactor pressure vessels and containment shells under dynamic loading

The effects of high strain rate, dynamic biaxial loading and deformation mode (tension, shear) on the mechanical properties of AISI 316 austenitic stainless steel in as-received and pre-damaged (creep, LCF) conditions are reported. This research was conducted to assess the performances of the containment shell of fast breeder reactors. The results of this research have been utilized to prepare similar investigations for SA 537 Class 1 ferritic steel used for the containment shell of LWR. The first results of these investigations are reported. A programme to study the mechanical properties of plain concrete with real size aggregate at high strain rate is described.     

Material properties for reactor pressure vessels and containment shells under dynamic loading

The effects of high strain rate, dynamic biaxial loading and deformation mode (tension, shear) on the mechanical properties of AISI 316 austenitic stainless steel in as-received and pre-damaged (creep, LCF) conditions are reported. This research was conducted to assess the performances of the containment shell of fast breeder reactors. The results of this research have been utilized to prepare similar investigations for SA 537 Class 1 ferritic steel used for the containment shell of LWR. The first results of these investigations are reported. A programme to study the mechanical properties of plain concrete with real size aggregate at high strain rate is described.     

Channeling radiation from quasicrystals: methods

Recently a class of quasicrystals has been discovered experimentally which exhibit quasiperiodicity along one direction and periodicity along all others. We have numerically calculated the transverse wavefunctions and energy eigenvalue spectrum of relativistic electrons channeled by the planes perpendicular to the quasicrystal (QC) axis for a simplified model of such a one-dimensional quasicrystal. The calculations were performed by using both conventional crystal approximant techniques and, for the first time, by a direct technique which makes use of the quasicrystalline model itself. The results given by the two methods agree well with each other. These wavefunctions and eigenvalue calculational procedures are the main ingredients in the computation of the channeling radiation intensities and spectra from such channeled electrons in the considered QCs, as will be reported in a future paper.     

六面体单元中X射线能量沉积算法及其在圆柱壳体结构中应用研究

为了对三维条件下的X射线热击波传播问题进行数值模拟,需首先解决能量沉积计算的问题。本文采用计算能通量矢量在面单元上积分的方法,给出了一种六面体单元中X射线能量沉积算法,并计算了有限长圆柱壳体构形在X射线正入射及斜入射条件下的能量沉积分布。结果表明:对于正入射,沉积能量沿方位角近似呈余弦分布,与理论解吻合,在半径方向上,能量沉积由表层向内部快速递减;对于斜入射,在壳体内外侧及柱体端面均会出现能量沉积区域,整个沉积能量分布呈现出明显的边界效应。     

A model for the normal stress dependence of intergranular cracking of irradiated 316L stainless steel in supercritical water

The intergranular cracking behavior of irradiated 316L stainless steel in supercritical water (SCW) was found to be strongly dependent on the local grain boundary normal stress. Tensile specimens of 7 dpa proton irradiated 316L stainless steel were strained in 400 °C SCW to 2%, 5%, and 10% macroscopic plastic strain. The cracking behavior was characterized according to the distributions of cracked grain boundary plane surface trace inclinations to the tensile axis and the Schmid factors of the grains adjacent to the cracked boundaries. Cracks occurred preferentially along grain boundaries with trace inclinations perpendicular to the tensile axis and adjacent to grains with low Schmid factors. There was also a slight increase in cracking propensity for grain boundaries adjacent to grains with high Schmid factor mismatch. The normal stress dependence of intergranular cracking was confirmed by developing and applying the Schmid-Modified Grain Boundary Stress model which characterizes the normal stress acting on a grain boundary as a function of the inclination of the grain boundary plane to the tensile axis and the flow stress of the grain, as estimated from its Schmid factor. By applying this model, the Schmid factor dependence of intergranular cracking could be predicted from the distributions of cracked grain boundary trace inclinations to the tensile axis.     

Amorphous phase and anisotropy induced by glancing incident ion beams in Co-Nb films

Co-Nb amorphous films were prepared with the aid of glancing incident ion beams during deposition process. Influence of ion interaction to phase formation and fine microstructure was studied. Amorphous range is about 19 to 63 at.% Co fractions, which is wider than that obtained by perpendicular ion bombardment (28 to 68 at.% of Co fractions). A ripple or a bamboo raft pattern with nano-scale periodicity is observed in the TEM (transmission electron microscopy), SEM (scanning electron microscopy) and AFM (atomic force microscopy) images. The sizes of the image patterns are characterized by correlation length calculated from height-height correlation function (HHCF). The correlation length along the ion incidence is longer than that perpendicular to the ion incidence. Analysis regards that the glancing incident ion beams have high efficiency in both rapid cooling and ion mixing (IM). The main pattern feature in the images mainly comes from surface erosion. Other fine microstructure and the difference among the images result from surface diffusion or viscous flow effect.