Neutron Activation Cross Section of Molybdenum Isotopes at 14.8 MeV

The neutron activation cross sections of Mo isotopes have been measured for the 14.8 MeV neutron. The cross sections have been determined with reference to the known ²⁷A1 (n, α)²⁴Na and the ²⁷Al(n, p)²⁷Mg reactions. The cyclic activation method was employed for the γ-ray measurement of short-lived nuclei. A 55 cm³ Ge(Li) detector was used for the measurement of γ-ray spectra. Cross section data are presented for (n, 2n), (n, p) and (n, a) reactions on Mo isotopes. The cross sections of (n, np) reactions on ⁹⁸Mo are also presented. The exponential dependence on (N-Z)/A of the (n, p) reaction cross sections are discussed.     

Measurement of Thermal Neutron Cross Section of ^135Cs

350keV高压倍加器辐照装置的真空系统自2005年1月安装完成后，到目前已运行12个月，其运行状况正常。     

Measurement of Neutron Inelastic Scattering Cross Section for (56)~Fe from 1 MeV to 3 MeV

正Iron is a widely used material in nuclear reactor.Neutron inelastic scattering is an important energy loss mechanism.Its precision affects reactor calculations and radiation shielding design.1.2 MeV and 2.5 MeV neutrons were produced     

8.17 MeV中子与天然铁作用的次级中子双微分截面测量

测量了8.17 MeV中子与天然铁作用的次级中子双微分截面,测量角度为30°～150°,共11个角度,采用n-p散射作为标准截面进行归一.测量数据用Monte-Carlo方法进行了模拟,以进行中子注量衰减、多次散射和有限几何修正.将测量结果与评价数据及其它测量数据进行了比较与分析.实验测量结果对数据评价、理论模型检验及实际应用等具有重要的意义.     

Measurement of Gamma-Ray Production Cross Sections of Iron for Incident Neutron Energies between 6 and 33 MeV

Measurement of differential γ-ray production cross sections, i.e. (n, x γ) cross sections, of Fe was made for neutron energies from 6 to 33 MeV. Neutrons used in the experiment were white neutrons produced with (p, n) reactions by 35 MeV protons using a thick Be target. The neutron energy was analyzed by the time-of-flight method and bunched into 3 MeV wide energy bins, for each of which the spectrum of secondary γ-rays produced in an Fe sample was measured by a BGO scintillator at an angle of 144° to the neutron beam direction.

The obtained (n, xγ) cross sections agreed well with other data and the evaluated data file of ENDF/B-IV at neutron energies below 15 MeV where data were existing. The JENDL-3 file overestimated the γ-ray spectra at γ-ray energies of 3 to 7 MeV. The present work newly provided the data in the neutron energy range above 20 MeV. The GNASH calculation made by Young reproduced the measured data fairly well even at these higher energies.     

Discussion of Data Difference Among Measured Thermal Neutron Cross Section of ^135Cs

“天光一号”系统采用诱导空间非相干（FEISI）和像传递技术实现了对靶平面的均匀辐照，但该技术并不能确保光束在激光传输路径上的近场分布均匀。虽然MOPA系统中大多数光学元件表面平均光通量不大于 1J／cm^2，     

235U快中子核反应截面协方差评价

本文基于最小二乘不确定度传递方法,建立²³⁵U中子裂变核反应截面模型依赖型与非模型依赖型协方差评价体系。通过针对实验测量较丰富的中子反应总截面、辐射俘获、(n,2n)等核反应实验数据不确定度源项分析,为协方差评价提供实验基础,并给出对应核反应截面的非模型依赖型协方差评价数据。通过开展快中子能区²³⁵U核反应理论模型参数灵敏度计算与分析,导出实验测量缺乏的核反应截面模型依赖型协方差评价数据。经上述系统评价,所得协方差数据与核反应截面中心值研究过程自洽、物理合理,并按国际标准ENDF-6格式输出,便于核工程用户使用。     

Double-Differential Neutron Emission Cross Sections of 6Li and 7Li at Incident Neutron Energies of 4.2, 5.4, 6.0 and 14.2 MeV

Energy-angle double-differential neutron emission cross sections of lithium isotopes were measured at incident neutron energies of 4.2, 5.4 and 14.2 MeV for ⁶Li and of 5.4, 6.0 and 14.2 MeV for ⁷Li using a time-of-flight spectrometer. Care was taken in background subtraction and in data correction for sample-size effects. Detailed comparison of the present results was made with the evaluated data in JENDL-3PR1. A spectrum fitting method was used to extract the ^6,7Li(n, n'x)α and (n, 2n) reaction cross sections. Neutrons emitted from the (n, 2n) reactions were well described by the conventional evaporation model. A simple calculation with a final-state Coulomb interaction was effectively applied for the ^6,7Li(n, n'x)α reactions. Angle-integrated cross sections of the ⁷Li(n, n't)α reaction were in good agreement with the JENDL-3PR1 data except the data measured at 6.0MeV. The angular distributions of elastically and inelastically scattered neutrons were successfully analyzed with the coupled-channel method at the incident neutron energy of 14.2 MeV.     

Cross Section for Radiative Electron Capture(REC) by 20-80 MeV CL Ions Incident on C and CU Foils

Radiative electron capture (REC) cross sections for 40-80 MeV Cl ions incident on thin C foils are reported and compared with previous results using Cu targets. We find that the measured REC cross section per K vacancy scales according to the number of "free" electrons on the target atom, i. e., those bound target electrons with a velocity much less than the incident projectile velocity. Comparison is made with the free-electron theory of Bethe and Salpeter and good agreement is obtained. Experimental and theoretical results are compared with those of Lindskog et al., and consideration is given to different ways of computing the K-shell binding energy of the projectile at the time of REC which enters into the calculation of the theoretical REC cross section in an important way.     

国产Am-Be中子源能量低于1.5MeV中子所占份额的实验测定

本工作提出了测定Am Be中子源发射的能量低于1.5MeV中子所占份额的1种实用实验方法。用4.438MeVγ射线伴随的飞行时间法测量了中子源的局部中子谱（n₁群中子）。通过已准确测量的中子源发射4.438MeVγ射线与中子强度的比值(R=R_γ/S_n)和n₁群中子谱与测量的能量为1.5MeV以上中子总谱在3.2MeV能量处归一后的面积比值,求得国产Am-Be中子源能量低于1.5MeV中子的所占份额为(19.1±1.9)%。     

Measurements of the Thermal Neutron Macroscopic Absorption Cross Section for Neutron Absorbing Layers

Objective of this study is measuring the macroscopic cross section of a neutron absorbing layer for thermal neutrons. For this purpose a neutron source and BF ₃ detector have been applied. For measuring macroscopic cross section of thermal neutrons by the \( I = BI_{0} e^{{ - \sum\nolimits_{tot} t}} \) Formula, it is necessary to provide suitable geometric conditions in order to assume the production and build-up coefficient to be the unit value (=1). To fulfill required conditions for this assumption, surface of the detector is covered with a 2 mm thick layer of cadmium. Radiation window of the detector has a 3 cm diameter, situated directly in front of the source. By placing the cadmium cover over the detector, variation of \( Ln{\frac{{I_{0}^{{}} }}{I}} \) values verses thickness of absorbent layer, renders linear function behavior, making it possible to measure the macroscopic cross section. The next stage is applying the MCNP code by simulating F1 tally and cosine-cards for calculating Total Macroscopic Cross-Section. Validation of this study is achieved through comparison of simulation by the MCNP code and results rendered by experiment measurements.     

Calculation of Double Differential Cross Section for Fast Ion and Electron Impact Ionization of Atoms

The theory of the energy and angular distribution of electrons ejected in electron-atom and ion-atom collisions, within the framework of Born approximation, is discussed. Particular attention is paid to the case where the incident ion carries along its own electrons. Examples are given for e, H+, and He+ collisions with He. It is shown that for fast collisions, excellent agreement with experiment is obtained for electron impact and fairly good agreement for proton and He+ impact when both projectile and target ionization are taken into account.     

Measurements of Fast Neutron Scattering Cross Sections of Li-7 at 11.0 and 13.0 MeV

The secondary coolant of pressurized water reactors is buffered to slightly alkaline pH by ammonia or amines in order to suppress corrosion. 3-Methoxypropylamine (MPA) is one of the promising alternative amines. The thermal decomposition of MPA was studied under two conditions: (i) a dissolved oxygen (DO) concentration of less than 5 ppb at 280°C for 1.5 h and (ii) a DO concentration of 20 ppb at 70°C for 2 h. The initial MPA concentration was 10 ppm. After the tests, concentrations of MPA and carboxylic acids were measured. Approximately 9 to 15% of MPA was decomposed after the tests. Carboxylic acid concentrations were as follows: (i) formate 110 ppb, acetate 260 ppb and propionate 400 ppb at 280°C, and (ii) formate less than 2 ppb, acetate 60 ppb and propionate 1270 ppb at 70°C. The reaction mechanism of MPA decomposition was estimated from the present experimental results. At 280°C, the hydrolysis of the ether bond initiates the decomposition, and the subsequent bond cleavage of C-N and/or C-C occurs. At 70°C, hydrogen abstraction by an oxygen molecule is the initiation reaction. MPA radicals and HO₂ or C1 compounds propagate a chain reaction and result in a relatively high yield of propionate.     

Differential Cross Section Measurement for ~6Li(n,t)~4He Reaction at 3.67 and 4.42 MeV

Using a gridded ionization chamber, the differential cross sections for ~6Li(n,t)~4He reaction were measured at 3.67 and 4.42 MeV. The neutrons were produced with D(d,n)~3He reaction. Absolute neutron flux was determined through ~(238)U(n,f) and H(n,p) reaction. The result at 3.67 MeV is almost 90 degree symmetry but it is obviously forward peaked at 4.42 MeV in the center of mass system.     

氟离子碰撞引起的钽L壳层X射线产生截面测量

测量了20～55 MeVF5+离子和Ta原子碰撞中Ta产生的L壳层X射线.计算了Ta的L各支壳层产生截面的比值和总截面的比值.利用L壳层的辐射跃迁几率、CrosterKroning跃迁几率和L亚壳层的荧光产额,将平面波波恩近似（PWBA）和ECPSSR理论计算的电离截面转换为L层X射线产生截面,并与实验结果进行比较.结果表明,σ(Ll）/σ(Lα)、σ(Lγ)/σ(Lα)和σ(Ltotal)/σ(Lα)与ECPSSR理论预测结果吻合较好,σ(Lβ)/σ(Lα)较两种理论预测值均偏小.     

Measurement of Neutron Total Cross Section of Silicon at 146-and 53.5-keV Windows

The process constituting the elements of the method for treating high-level liquid waste with addition of reducing agent at temperatures above 1,873 K were examined applying thermogravimetry and X-ray diffractometry to sample mixtures of the platinum metal oxides RuO₂, Rh₂O₃, PdO and of Re₂O₇, with and without addition of TiN as reducing agent. The addition of TiN reducing agent proved to induce reduction of the platinum metal oxides at temperatures far below those of thermal decomposition occurring in the absence of reducing agent. The presence of reducing agent further proved to reduce Re₂O₇ to ReO₃ at 373K, to ReO₂ at 773 K and to Re metal at 1,073 K. At around 773 K disproportionation reconverted part of the ReO₃ formed at 373K to ReO₂ and Re₂O₇. Thus, sublimation of the Re₂O₇ in starting material which occurs at 523 K in the absence of TiN was eliminated, and occurred only at 773 K on the Re₂O₇ that was regenerated at that temperature by disproportionation of the converted ReO₃. Alloys of Ru, Rh and Pd resulting from the above treatment with TiN proved to agree with what is indicated from phase diagrams. Among the alternative compounds existing in the Rh-Ti and Rh-Ti binary systems, however, solely Ru-Ti proved to have been produced.     

Total Neutron Cross Section in Heavy Ice at 77 and 15 K for Neutron Energies between 0.3 and 100 meV

A 10MW High Temperature Gas Cooled Reactor (HTR-10) designed by the Institute ofNuclear Energy Technology (INET) of Tsinghua University is being constructed now. The steam generator (SG) of the HTR-10 is one of the most important facilities for reactor safety. In order to investigate the thermal-hydraulic performance of the SG, a full scale HTR-10 Steam Generator Two Tube Engineering Model Test Facility (SGTM-10) was installed and tested at INET. This paper describes the SGTM-10 in detail. The test assembly of the SGTM-10 simulates practical thermal and structural parameters of the HTR-10. The SGTM-10 consisted of three separated loops, primary-helium loop, secondary-water loop, and third-cooling water loop. There are two parallel tubes arranged in the test assembly. The main experimental equipment is shown in this paper. Analysis shows that for once-through steam generator simulation experiment, the electric-heated simulation method could not match practical operating condition. The results may not reflect true phenomena. The main results of experiments, for example effects of the outlet pressure, effects of the heating power, effects of the inlet sub-cooling are described. Experiments indicated, when the heat load of the HTR-10 is more than 30% the SG will be stable.     

Evaluation of Cross Sections of Photonuclear Reactions for ~(90,91,92,94,96)Zr Below 30 MeV

The study of the properties of nuclei near to the closed neutron shell at N=50 is a subject of widespread interest. The accurate photonuclear data play an important role in nuclear science and technology. In this work, the experimental data of photonuclear up to 30 MeV for ~(90,91,92,94,96)Zr were evaluated which is impotant to radiation damage, radiation safety, reactor dosimetry. The theoretical calculation were used for supplement to some energy where the measured photonuclear data are scarce. The recommended photonuclear data for ~(90,91,92,94,96)Zr were obtained based on evaluated and calculated data and compared with existing measured data.