500A MeV 56Fe诱发乳胶核反应慢粒子产生

本文对500A MeV ⁵⁶Fe诱发乳胶核反应慢粒子产生进行研究。实验结果表明,黑径迹粒子、灰径迹粒子和重电离粒子平均多重数随靶核增大而增加;黑径迹粒子平均多重数与入射能量无关,灰径迹粒子平均多重数随入射能量增加而增加;灰径迹粒子和重电离粒子平均多重数随黑径迹粒子数的增加而增加;重电离粒子平均多重数随灰径迹粒子数的增加而增加,而黑径迹粒子平均多重数随灰径迹粒子数的增加先增加后趋于饱和;灰径迹粒子平均多重数随重电离粒子数的增加而增加,而黑径迹粒子平均多重数随重电离粒子数的增加先增加后趋于饱和。     

4.5 AGeV/c ~(16)O-Em作用末态产生粒子前后关联研究

介绍了 4 5AGeV/c16O Em作用末态产生粒子的多重数分布 ;讨论了簇射粒子、灰径迹粒子和黑径迹粒子向前后半球内发射的关联。实验结果表明 :簇射粒子、灰径迹粒子在前后半球内的分布明显不同 ,而黑径迹粒子多重数在前后半球内的分布并无显著差别 ;在前半球内 ,簇射粒子及灰粒子数随后半球内的簇射粒子及灰粒子数的增加明显增加 ,且增加幅度随束流质量的增加而提高 ;后半球内的簇射粒子及灰粒子平均多重数随前半球内的簇射粒子及灰粒子数的增加而增加 ,但增加的幅度随射弹质量的增加而减弱。     

4.5AGeV/c 16O-Em 作用末态产生粒子前后关联研究

介绍了4．5AGeV/c ^16O-Em作用未态产生粒子的多重数分布；讨论了簇射粒子、灰径迹粒子和黑径迹粒子向前后半球内发射的关联。实验结果表明：簇射粒子、灰径迹粒子在前后半球内的分布明显不同，而黑径迹粒子多重数在前后半球内的分布并无显著差别；在前半球内，簇射粒子及灰粒子数随后半球内的簇射粒子及灰粒子数的增加明显增加，且增加幅度随束流质量的增加而提高；后半球内的簇射粒子及灰粒子平均多重数随前球内的簇射粒子及灰粒子数的增加而增加，但增加的幅度随射弹质量的增加而减弱。     

高能重离子诱发核反应中灰粒子产生

采用ＥＭＵ０１国际合作组的原子核乳胶为探测器,系统地研究了能量为１４．６,６０,２００ＧｅＶ／ｕ的＾１６Ｏ核,２００ＧｅＶ／ｕ的＾３２Ｓ诱发核反应产生的灰粒子平均多重数及角分布,以描写相对论性核－核碰撞的ＬＵＣＩＡＥ模型为基础,进行ＭｏｎｔｅＣａｒｌｏ模拟的结果与实验数据一致。     

Ar射频放电特性随时间演化的PIC/MCC模拟

采用等离子体粒子模拟方法(PIC/MCC)方法对一维模型模拟了容性耦合等离子体(CCP)源放电过程中等离子体的动力学行为。在模拟氩气放电的过程中,综合考虑了电子与Ar之间的弹性碰撞、激发、电离以及Ar与Ar+之间的弹性碰撞和电荷交换过程。由模拟结果可知,射频极板附近鞘层区域在极短时间内形成,其厚度随着时间的增加而增厚;而射频极板处的粒子通量随着时间的增加逐渐减小。经过一段时间后,射频极板处平均粒子通量、平均电流以及鞘层平均厚度逐渐趋于平衡。在鞘层区域电流主要由位移电流构成,在等离子体区域电流主要由传导电流贡献。最后讨论了达到平衡态后等离子体密度、电势、电场强度和能量的空间分布情况。     

用宇宙线重核测试CR-39径迹探测器性能

本文介绍用宇宙线重核测定CR-39径迹探测器性能的方法。根据穿透探测器重核粒子径迹的蚀刻速率比V=Vr/V_g,测试了国产CR-39的探测灵敏度、一致性和均匀性。     

α粒子微束定点照射--细胞的放射生物学效应及精确性分析

进行微束试验的关键是能够精确地控制照射的粒子数和将粒子准确地射入受照射位点.该研究通过对哥伦比亚大学单粒子微束装置在精确性、准确性以及各项指标的分析发现该装置可精确地控制照射粒子数,精确率为98.4%.同时,它可将α粒子准确地射入受照射位点,束半径为34,达到设计4的标准.在对细胞特定位点如细胞质照射上,粒子击中细胞质至少一个位点的概率为90%,在这一过程中的偶然核击中率,对大多数照射剂量(8个粒子)均小于0.8%.应用该微束装置的放射生物学研究发现单个α粒子仅导致大约20%的致死率,其存活率曲线类似于用常规照射获得的平均粒子存活曲线.诱变试验首次证实单个α粒子在AL细胞的CD59基因位点可诱导出比对照高出3倍数量的诱变子,诱变率随粒子数的增加而增加.这一结果不同于常规照射中,诱变率在高剂量照射后下降的结论.     

核径迹电化学蚀刻过程中某些基本参数的研究

本文采用聚碳酸酯膜(Makrofol)和~(241)Am 标准面源,实验观测了核径迹电化学蚀刻坑的平均直径和径迹密度与聚碳酸酯膜受照后存放时间、α粒子注量等的关系,为这种核径迹探测方法的应用提供实验数据。     

CR—39探测器的α粒子径迹研究

研究了以KOH作蚀刻液、恒温60℃蚀刻时CR-39探测器的α粒子径迹情况。实验表明,α能量越低则径迹显现时间越短;能量低至70keV时,CR-39就不能显出径迹。径迹直径随蚀刻时间延长而增大。能量1—4MeV时径迹随能量变化较快;超过4MeV时,这一变化逐渐减小。当α粒子的入射角大于40°时,实际角度和根据径迹参数而求得的角度非常一致;而小于此角时,两者相差较大。     

固体核径迹的平均直径与密度随蚀刻温度和蚀刻剂浓度的变化

实验观察了固体核径迹的平均直径和径迹密度随蚀刻剂浓度、蚀刻温度的变化关系。实验采用聚碳酸酯膜(Makrofol)为探测器,化学预蚀刻与电化学蚀刻相结合,蚀刻剂浓度分别为5、6和6.85mol/L 的 KOH 溶液,蚀刻温度分别为30、40、50和60℃,实验结果表明,在本实验条件下,核径迹的平均直径和径迹密度均随蚀刻温度和蚀刻剂浓度的升高而明显增大。     

起伏振动下倾斜管内单相流流动阻力特性分析

起伏振动状态下单相流流动阻力的正确计算对漂浮核电站的安全性有显著影响。实验研究了不同起伏振动工况和流动工况对倾斜圆管通道内单相水摩擦压降的影响，提出了方便计算的振动摩擦阻力系数。结果表明，振动摩擦压降大于稳定状态的，并呈周期性波动，波动周期与振动频率一致。振动摩擦阻力系数平均值随雷诺数和倾角的增大而减小，随管径和振动频率的增大先增大后减小，随振幅的增大而增大。通过实验数据拟合得到起伏振动下倾斜管内单相水振动摩擦阻力系数计算经验关系式，计算结果与实验结果吻合较好，为起伏振动单相水流动阻力的计算提供了新思路。     

自然循环系统摇摆条件下棒束通道内传热特性研究

棒束燃料元件子通道间流体存在搅混与横向二次流,流动及阻力特性相较矩形通道、圆管等简单通道更为复杂。核动力舰船、船舶、小型浮动核电站等会受到海浪影响,经常处于倾斜、摇摆、垂荡等瞬变运动下。目前的相关研究多集中在低压工况的研究领域,高温高压自然循环运动条件下的研究较少。本文采用实验研究方法,对自然循环系统摇摆条件下棒束通道内流动传热特性进行了研究,获得了过冷沸腾和饱和沸腾两种条件下摇摆角度和摇摆周期对棒束壁面温度变化和传热系数的影响,并获得了摇摆周期内棒束通道内的传热系数计算关系式。结果表明,饱和沸腾传热系数变化比过冷沸腾的剧烈;在本文实验工况范围内,棒表面传热系数波动幅值随着摇摆幅度的增大而增大;摇摆条件下棒束通道过冷沸腾和饱和沸腾工况时均传热系数基本不变。     

气冷微堆燃料设计的中子学特性影响研究

为分析气冷微堆燃料设计的中子学特性影响,基于方形燃料组件模型,利用蒙特卡罗程序RMC研究了TRISO颗粒、燃料芯块在燃料设计中的主要参量对组件中子学特性的影响。研究结果表明,燃料颗粒体积占比和包覆层厚度不变时,组件寿期随燃料核芯直径的增大先显著增大,而后趋于平稳;燃料颗粒体积占比和燃料核芯直径不变时,组件寿期随包覆层厚度的增大而减小;燃料装载量不变时,芯块直径增大,组件寿期显著增大,而芯块高度影响较小;无燃料区厚度的增加对组件中子学特性有明显的负面影响,基体材料密度、基体杂质硼当量对组件中子学特性的影响较小。研究结果将为后续气冷微堆包覆颗粒弥散燃料的设计优化提供指导。     

Improvements in the description of the multiplicities of the prompt neutrons emitted in fission

Various parameterizations of the multiplicity distribution of prompt neutrons from nuclear fission are investigated. The currently accepted formalism is found to fail for those fission processes which release on average a low number of neutrons. Based on realistic assumptions regarding binary fission, an improved multiplicity distribution formula gives much better agreement with the experimental data. Explicit details of the practical usage of the new formalism are presented. Finally, it is shown that for spontaneously fissioning isotopes, it is possible to calculate the variance of the neutron multiplicity distribution from a knowledge of the mass yield and the variances of the neutron multiplicity distributions of the individual fission fragments.     

Experimental measurement of effective thermal conductivity of packed lithium-titanate pebble bed

Lithium titanate is a promising solid breeder material for the fusion reactor blanket. Packed lithium titanate pebble bed is considered for the blanket. The thermal energy; that will be produced in the bed during breeding and the radiated heat from the reactor core absorbed must be removed. So, the experimental thermal property data are important for the blanket design. In past, a significant amount of works were conducted to determine the effective thermal conductivity of packed solid breeder pebble bed, in helium atmosphere, but no flow of gas was considered. With increase in gas flow rate, effective thermal conductivity of pebble bed increases. Particle size and void fraction also affect the thermal properties of the bed significantly. An experimental facility with external heat source was designed and installed. Experiments were carried out with lithium-titanate pebbles of different sizes at variable gas flow rates and at different bed wall temperature. It was observed that effective thermal conductivity of pebble bed is a function of particle Reynolds number and temperature. From the experimental data two correlations have been developed to estimate the effective thermal conductivity of packed lithium-titanate pebble bed for different particle Reynolds number and at different temperatures. The experimental details and results are discussed in this paper.     

Improved Los Alamos model applied to the neutron induced fission of 235U and 237Np

The Los Alamos model, with multiple fission chances, was upgraded to include the linear relation between the average prompt gamma ray energy and the average prompt neutron multiplicity. A global, model-free parameterization of this relation versus the charge and mass number of fissioning nuclei is obtained. The average fission fragment kinetic energy dependence on the incident neutron energy is also taken into account. Employing this model for the n+²³⁵U and n+²³⁷Np reactions, the prompt fission neutron spectra, the average prompt neutron multiplicity and the average prompt gamma ray energy are obtained in very good agreement with the experimental data, proving a better predictive power.     

Formation and evolution of oxygen vacancies in ZnO white paint during proton exposure

The formation and evolution of oxygen vacancies in ZnO white paint during <200 keV protons exposure was investigated using photoluminescence spectroscopy. After irradiation, the shape of photoluminescence spectra changes little, but the peak height decreases. With increasing fluence, the amount of doubly ionized oxygen vacancies decreases, while that for the singly ionized oxygen vacancies increases. The former can trap electrons in the conduction bands to become the singly ionized oxygen vacancies, leading to that the latter gradually becoming the major defects induced by irradiation. The increase in content of singly ionized oxygen vacancies due to the irradiation can also promote an increase in the amount of absorbed oxygen in the paint, enhancing the quenching effect of photoluminescence and thus decreasing the photoluminescence peak.     

具有导热的竖环形封闭腔内自然对流数值研究

以中国实验快堆堆坑为计算原型,采用有限容积法对具有导热的竖环形封闭腔内自然对流进行了二维层流稳态数值研究。数值计算结果表明：在相同Ra条件下,平均Nu随曲率的增加而增加,随纵横比的增加而降低,但在低Ra区,平均Nu几乎不随纵横比变化;在低Ra区,竖环形封闭腔内换热方式主要是导热,当Ra大于某一临界值后,腔内对流换热的作用显著增强,并随Ra的增大逐渐占据主导。     

多气泡对燃料颗粒应力分布的影响研究

利用有限元模拟方法建立了UO2弥散型燃料颗粒受内部多个气泡内压作用的模型,计算得到了燃料颗粒内部存在多个气泡时的应力分布结果。结果表明,当气泡沿x轴均匀排列时,y方向的最大正应力随气泡数量的增多而增大,且增大幅度逐渐减小,气泡对燃料颗粒内部最大正应力的影响存在极限;当存在多行气泡时,燃料颗粒内部x方向的最大正应力随气泡行数的增加而增大,y方向的最大正应力随气泡行数的增加而减小;气泡造成的燃料颗粒内部的应力集中效应随距径比的增大而减小。