Direct neutron spectrum measurement to validate Zr(n,2n) reaction cross-section at 14 MeV

Lithium zirconate, Li₂ZrO₃, is known as a candidate blanket material in a fusion reactor. Various neutronics benchmark experiments for zirconium have thus been carried out so far. According to the independent benchmark studies by two parties, the neutron spectrum calculations show fairly large overestimation for most evaluated nuclear data libraries. However, the reason has not yet been made clear up to now. The author's group expects it would be due to a problem of evaluation for the ^natZr(n,2n) reaction cross-section, because the cross-section measurement is basically not possible with the foil activation method for zirconium isotopes except for ⁹⁰Zr.In the present study, two neutrons emitted from ^natZr(n,2n) reaction have been measured directly to investigate the reason for the above overestimation. The measurement was done with our own special technique of detecting angle-correlated neutrons by the coincidence detection technique and the pencil-beam DT neutron source of FNS, JAEA. Angle-correlated energy differential cross-sections for ^natZr(n,2n) reaction were successfully measured. The obtained total cross-section above the emitted neutron energy of 800 keV was fairly larger than the one evaluated in JENDL-3.3. The total cross-section of ^natZr(n,2n) reaction was estimated by extrapolating the spectrum down to zero energy taking into account the nuclear temperature. The estimated cross-section value with the nuclear temperature of 1 MeV, which is larger than the one adopted in JENDL-3.3, was in acceptable agreement with JENDL-3.3. It is suggested from the result that the disagreement pointed out in the previous benchmark studies may be due to inappropriate nuclear temperature used in the evaluation. Further investigation of the nuclear temperature employed in the nuclear data evaluation should thus be carried out once again.     

Calculation of cross-sections for p+ Mo reactions up to 160 MeV

Proton-induced reactions on ^{92,94,95,96,97,98,100}Mo have been studied in the energy range from threshold to 160 MeV. All cross-sections for neutrons, protons, deuterons, tritons, helium and alpha particles emission have been calculated by using nuclear theoretical models which integrate the optical model, the intra-nuclear cascade model, direct, pre-equilibrium and equilibrium reaction theories. Theoretical calculations have been compared with existing experimental data; in most cases, the calculated results are in good agreement with the experimental data.     

Measurements and evaluation of the cross-section for helium elastic scattering from nitrogen

The cross-sections for the elastic scattering of alphas from natural nitrogen were measured at three laboratory scattering angles: 118°, 150° and 165° at non-Rutherford scattering energies from 2.5 to 4.0 MeV. Experimental data obtained in this work, together with all previously published data, were used for the cross-section evaluation. Model calculations with comparison and fitting to the experimental data were used for the evaluation of the cross-section. As a result of the work, the recommended cross-sections for scattering of alphas from nitrogen have been produced in the energy region of 1.6-4.6 MeV.     

Design of a prompt-gamma neutron activation analysis system on China Advanced Research Reactor

In this paper,computational methods are used to optimize the design of a prompt-gamma neutron activation analysis(PGNAA) system on China Advanced Research Reactor(CARR).Approaches are adopted for obtaining accurate neutron beam parameter and saving the computing time.For the radiation shielding design,the optimizing factors include the cost,weight,volume,machining convenience and background radiation at the detector position.Low background spectrum and high sensitivity are expected.The simulation results...     

截面畸变对小半径热煨弯管性能的影响

小半径热煨弯管在生产过程中会出现截面趋于椭圆、壁厚减薄或增厚等各种截面畸变,上述缺陷有可能会降低管道的承载能力。为了研究截面畸变对小半径热煨弯管性能的影响,以不同组合工艺参数煨制小半径热煨3D(D表示管道直径)弯管,通过截面几何尺寸分析、畸变分析、理化性能试验、微观组织分析等方法综合分析了3D弯管和常规5D弯管截面畸变、组织性能情况及其关联性。研究结果表明:(1)3D弯管增厚率和减薄率约是5D弯管的2倍,3D弯管圆度是5D弯管的2~4倍;(2)3D弯管截面畸变显著,各部位加热温度差异较大,使得组织形态或含量有所不同,导致3D弯管外弧侧、内弧侧及中性区等各部位力学性能数值分布较为离散;(3)多数弯管内弧侧强度都达不到标准的要求,强度大小顺序分别为弯管外弧侧、弯管中性区和弯管内弧侧,夏比冲击韧性大小顺序与强度恰好相反;(4)随着圆度的增加,内、外弧侧强度呈下降趋势,随着增厚率的增加,内弧侧强度呈下降趋势,随着减薄率的增加,外弧侧强度呈上升趋势。     

N-1静态安全潮流约束下的输电断面有功潮流控制

运用支路开断分布系数和直流潮流分析了输电断面的N-1静态安全有功潮流约束.根据断面有功潮流与N-1状态下支路潮流的关系,提出了衡量断面潮流控制合理性的原则.研究表明,断面有功潮流与N-1状态下支路潮流的关系随系统的发电模式以及负荷模式的变化而改变,从而导致了通过控制断面潮流来满足电网的N-1静态安全约束必然趋于保守,而直接运用线路开断后的计算潮流值进行N-1静态安全潮流分析将会显著提高输电断面的功率输送能力.     

A new cross-section generation model in the FAST code system and its application to gas- and sodium-cooled Generation IV fast reactors

The cross-section generation scheme employed in the 3D spatial kinetics PARCS code included in the FAST code system being used and developed at the Paul Scherrer Institute (PSI) is currently based on region-wise macroscopic cross-sections for reference conditions and their first-order derivatives with respect to the state variables. Since for some transients, feedback effects may likely not in this way be precisely approximated in their interrelations, this standard method was recently complemented for (hex, z) geometry by a more rigorous cross-section representation scheme. The main idea behind the new approach within the FAST code system is that of preparing sets of microscopic cross-sections for a studied design. The full library consisting of such isotopic tables is generated based on using the ECCO cell code of the code system ERANOS developed by the French Atomic Energy Commission (CEA) for a suitable range of temperatures and background cross-sections (σ₀) on a common grid. In the paper, this σ₀-model is described. In addition, within a detailed verification study needed due to its complexity, it is extensively compared to the standard method for both steady-state and transient conditions. Thereby use is made of current Generation IV fast-spectrum concepts. Reactivity and power evolution indicate overall good agreement of the two methods. Such a good consistence in various transient situations for systems characterized by different neutron spectra gives a large degree of confidence in the correct implementation and suitability of the microscopic cross-section methodology. Therefore, besides for the safety analysis of advanced fast-spectrum core concepts in general, it is foreseen, within the FAST code system, to use the σ₀-model for the assessment of uncertainty propagations in transient calculations in conjunction with the available ERANOS isotopic covariance matrices. The new development makes it also in principle possible to use the PARCS code as a reactor kinetics solver for severe accident analysis, allowing through the use of microscopic cross-sections to account for relocation of the core material during the accident.     

How price responsive is commercial electricity demand in the US?

We use monthly data for the lower 48 states in the US and 30-year period of 1991–2020 to estimate commercial electricity demand’s price responsiveness. Our key findings are: (1) the US commercial electricity demand’s statistically significant (p-value ≤ 0.05) own-price elasticity estimates are between ? 0.03 and ? 0.08; and (2) the size of these estimates has been slowly declining over time. Hence, price-induced conservation is unlikely effective, at least in the immediate future, to materially reduce the US commercial electricity consumption, thus justifying continuation of energy efficiency standards and demand side management programs.     

双排焊端QFN器件焊接工艺的改进研究

单排焊端的QFN焊接工艺趋于成熟,而双排及多排QFN器件给组装过程带来了很大挑战。生产中主要难点在于此类器件与其他较大型器件混装,对焊膏量、共面性的要求比较苛刻。通过分析焊膏印刷原理,同时在比对芯片焊端与PCB焊盘尺寸的基础上,采用调整模板开孔的方式来改善焊膏印刷,使焊接效果达到品质要求。介绍了PCB焊盘阻焊开孔及表面处理工艺、丝印参数在组装过程中的影响以及多排QFN返修工艺。     

Use of the local Pu-239 concentration as an indicator of burnup spectral history in DYN3D

Codes for reactor core calculations use few-group cross sections (XS) which depend on local burnup, given in terms of the energy produced per fuel mass (MWd/kgHM). However, a certain burnup value can be reached under different spectral conditions depending on moderator density and other local parameters. Neglecting these spectral effects, i.e. applying the summary-burnup value only, can cause considerable errors in the calculated power density.