高温度ACE格式连续能量点截面数据产生程序SIGACE的验证

以最新发布的ENDF/BVII.1评价库为基础, 使用SIGACE程序将低温ACE格式中子截面文件加工成较高温度的ACE格式文件, 生成了一个与温度相关的中子截面文档。 为校核截面数据, 选取ICT、 标准CANDU组件燃料温度反应性系数、 LWR栅格多普勒系数以及SEFOR基准题对SIGACE加工的核数据进行了验证。 基准题计算结果均与参考值符合较好, 表明SIGACE生成的高温度ACE格式截面数据可用于反应堆相关中子学参数的计算。 Based on the recently released ENDF/B-VII.1 library, high temperature neutron cross section files are generated through SIGACE code using low temperature ACE format files. To verify the processed ACE file of SIGACE, benchmark calculations are performed in this paper. The calculated results of selected ICT, standard CANDU assembly, LWR Doppler coefficient and SEFOR benchmarks are well conformed with reference value, which indicates that high temperature ACE files processed by SIGACE can be used in related neutronics calculations.     

MENDF—一个计算200 MeV以下裂变核数据的程序(英文)

基于球型光学模型、 预平衡发射和Hauser-Feshbach统计等理论, 编制了MENDF（Medium Energy Nuclear Data for Fission）程序, 该程序适用于裂变核在入射粒子能量低于200 MeV的中低能区的全套核数据计算。 对于中子和质子在200 MeV以下诱发的核反应, 其全截面、 反应截面、 弹性散射微分截面、 裂变截面和裂变中子谱、 5种发射粒子的单举截面和相应的能谱等理论计算值与相应的实验值基本符合。 MENDF在我国已被广泛用于核数据计算及建立中能核数据库。Based on the spherical optical model, pre equilibrium and Hauser Feshbach statistical theory, the code MENDF (Medium Energy Nuclear Data for Fission) is written to calculate a complete set of nuclear data for fission nuclei in the medium low energy region (≤200 MeV). For neutron and proton induced reactions below 200 MeV, the total cross sections, reaction cross sections, elastic scattering differential cross sections, fission cross section, energy spectra of fission neutron and five kinds of emitting particles, etc. are calculated by MENDF. The calculated data generally agree with their corresponding experimental data. MENDF is widely used for nuclear data calculation and to establish ENDF 6 formatted files for the medium low energy region in China.     

Discussion on Cross Section Measurement for D^-D Production around ψ（3770）

We give a brief discussion on the measurement of the cross section for D^-D production around the ψ（3770） resonance, and point out a new calculation of the cross sections based on the absolute measurements. Compared with single tag and double tag analyses, the new calculation provides us with many more opportunities to perform the cross section measurement.     

Microscopic Three-Body Force Effect on Nucleon-Nucleon Cross Sections in Symmetric Nuclear Matter

We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 potential including the contribution of microscopic three-body force. We investigate separately the effects of three-body force on the effective mass and on the scattering amplitude. In the present calculation, the rearrangement contribution of three-body force is considered, which will reduce the neutron and proton effective mass, and depress the amplitude of cross section. The effect of three body force is shown to be repulsive, especially in high densities and large momenta, which will suppress the cross section markedly.     

Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies

A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges.     

核子-核子碰撞截面的参数化公式

核子-核子碰撞截面(σ_NN)是描述原子核反应模型中的重要物理量。 核子-核子碰撞截面包括质子-质子碰撞截面（σ_pp）、中子-中子碰撞截面（σ_NN）和中子 质子碰撞截面（σ_np）, 它们随着核子能量与核物质密度的改变而变化。人们在目前研究中提出了多种核子-核子碰撞截面关于能量和核物质密度的参数化公式,通过计算12C+12C的完全反应截面,比较了不同入射能量下使用各种核子-核子碰撞截面参数化公式对12C完全反应截面的影响。 The nucleus-nucleus cross sections(σ_NN) include the proton-proton cross section, neutron-neutron cross section, and neutron-proton cross section. σ_NN change with the variations of the incident energies and the densities. Some parameterizations of σ_NNas a function of incident energy and density have been proposed in the theoretical and experimental study of nuclear reactions. Through the calculation of reaction cross sections of 12C+12C at different energies, the effect of different σ_NN parameterizations in the reaction cross sections of 12 are studied.      

Theoretical Analysis of Generalized Oscillator Strengths for Helium by R-Matrix Method

The high-energy electronic-impact excitation cross section is directly proportional to the generalized oscillators trength (GOS) of the target atom. The generalized oscillator strengths of helium atom from the ground state to the excited states (2^1S, 2^1P and 3^1D) are calculated using the updated R-matrix codes within the first Born approximation. Our calculation results are in good agreement with the previous theoretical and experimental results at high incident energies. In order to treat the bound-bound and bound-continuum transitions in a unified manner, the GOS density is defined based on the quantum defect theory. We calculate the GOS densities of ^1S, ^1p and ^1D charmels, namely the complete high-energy collision cross sections of electronic-impact excitations into all the n^1S, n^1P and n^1D excited states. In addition to high-energy excitation cross sections, a scheme to calculate the excitation cross sections for entire incident energy range is discussed.     

Halo Effect on Direct Neutron Capture Process

We calculate the capture cross sections of the ^10Be(n,γ) ^11Be reaction by means of the asymptotic normalization coefficient method and demonstrate the halo effects on the capture cross sections for the direct radiative neutron capture where a p-, s- or d-wave neutron is captured into an s-orbit or p-orbit in ^11Be by emitting an E1 γ-ray, respectively. The result shows that the enormous enhancement of the capture cross section is just due to the large overlap of the incident neutron wave with the extended tail of the ha/o, which is clearly illustrated by the reduced transition amplitude function.     

Roles of Isospin in Evaporation Residue Cross Section as a Probe of Nuclear Dissipation

The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.     

Electron impact excitation of helium atom

A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.     

西安脉冲堆127I嬗变计算方法与实验验证

为了开展129I的热中子嬗变的研究,在西安脉冲堆上开展了127I靶件辐照实验。以探索实验条件,对127I靶件的嬗变率进行了蒙特卡罗计算,并与实验测量值进行了比对。利用NJOY程序,以ENDF/B VII.0库为基础,制作了127I在西安脉冲堆堆芯辐照温度下的MCNP格式截面库,与MCNP自带库(ENDF/B VI.2)同温度下截面库进行了比较,在不可分辨共振区做了改进,使用新制的截面库,利用MCNP程序对ORIGEN2数据库中的127I辐射俘获截面进行了修正,结合ORIGEN2程序分析了127I靶件在西安脉冲堆实际辐照后的嬗变率和核素的变化,研究了中子能谱和辐照时间对靶件嬗变计算的影响。使用MCNPX自带的燃耗模块CINDER90对127I靶件的嬗变情况进行模拟,结果与ORIGEN2基本一致,与实验数值有2%~3%的偏差,主要原因是MCNP计算中子通量密度存在误差。     

JMCT程序在线多普勒展宽研究

在核反应堆堆芯物理分析中, 考虑燃料核素的多普勒效应对反应性的影响是必要的. 基于最小二乘拟合法, 在自主蒙特卡罗粒子输运程序JMCT中开发了在线多普勒展宽功能. 在300-3000 K的温度范围内, 利用核数据处理程序(NJOY)制作了系列温度点下的连续能量核数据. 在统一的能量网格上, 进行最小二乘拟合, 得到拟合参数. JMCT利用这些拟合参数, 快速计算得到任意温度的核数据, 用于输运计算. 计算结果表明, 拟合得到的核数据与NJOY制作的核数据符合很好, 满足精度要求. JMCT临界模型计算结果表明, 拟合参数计算有效增殖因数k_eff与直接采用NJOY加工得到核数据的计算结果吻合.     

混合评价核数据库HENDL1.0/MG/MC研制

根据世界几个主要核评价数据库,如ENDF/B 6(美国)、JEF 2.2(欧盟)、JENDL 3.2(日本)、BROND 2.2(俄罗斯)、CENDL 2.1(中国)和FENDL 2(IAEA/NDS),兼顾聚变、裂变以及聚变 裂变次临界混合堆设计研究的多种需要,经过甄别、筛选,最后集成为包含213个核素的基本评价文件,名为HENDL1.0/E的核评价数据库.在此基础上,利用目前流行的群常数加工程序系统NJOY和输运截面制备程序TRANSX制作两套用于中子或/和光子输运计算的输运截面工作库:①参考Vitamin J能群结构制作了175群中子和42群光子、中子 光子耦合多群工作数据库HENDL1.0/MG,可用于离散纵标Sn法程序计算;②连续能群结构、紧凑ENDF(ACE)格式中子截面库HENDL1.0/MC,可用于蒙特卡罗方法输运计算,如MCNP.另外还制作了可用于燃耗(嬗变)计算的燃耗库BURNUP.LIB和响应函数库RESPONSE.LIB两个专用数据库.同时,也对HENDL1.0综合评价核数据库的有效性进行了抽样测试、基准检验和初步确认. A Hybrid Evaluated Nuclear Data Library(HENDL) named as HENDL1.0 has been developed by Fusion Design Study (FDS) team of Institute of Plasma Physics, Academia Sinica (ASIPP) to take into account the requirements in design and research relevant to fusion, fission and fusion-fission sub-critical hybrid reactor. HENDL1.0 contains one basic evaluated sub-library naming HENDL1.0/E and two processed working sub-libraries naming HENDL1.0/MG and HENDL1.0/MC, respectively. Through carefully comparing...     

基于点截面的快堆组件均匀化参数计算方法

快中子反应堆的中子学计算中,少群参数的计算精度直接影响最终的计算精度。通过直接利用点截面的方法产生具体问题的精细群截面,随后进行组件输运计算并以获得的中子通量密度分布归并能群从而得到组件的均匀化少群参数,可以较精确地考虑中等质量核素在中高能量段具有的非常强烈的弹性散射共振效应以及全能量段存在的多核素共振干涉效应等问题。计算结果表明,由点截面产生的细群截面误差均在1%以内,进行能谱计算并利用该能谱归并能群得到少群参数的误差也在1%以内。随着截面精度的改善,最终堆芯计算的精度得到明显提升。     

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit of the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.     

快堆中子学计算程序NECP-SARAX的改进与验证

NECP-SARAX是西安交通大学NECP团队开发的用于快中子反应堆的中子学程序系统。为准确处理快中子反应堆中中等质量核素散射共振以及非弹性散射导致的复杂的中子慢化效应,SARAX程序最初采用连续能量的蒙特卡罗方法计算中子能谱从而获得堆芯计算使用的有效多群截面。由于蒙特卡罗程序计算效率低,且在低能量段统计偏差较大,提出采用基于点截面的超细群方法计算中子慢化能谱,避免了蒙特卡罗方法产生参数时存在的缺陷。堆芯计算采用多群中子输运,通过优化简化几何建模,改进了程序的实用性。采用多种微扰方法计算堆芯各种反应性系数,提出了基于中子输运微扰理论的虚拟密度方法以计算堆内组件变形导致的反应性变化。在进行堆芯瞬态计算时,采用了点堆和改进准静态两种方法,可用于一般快堆和快谱ADS的典型事故分析。OECD发布的一系列快堆基准题测试表明,SARAX程序在快堆计算中具有良好的精度,达到了与国外著名快堆程序相当的水平。有效增殖因子与连续能量的蒙卡计算结果相比偏差在300 pcm以内。同时,由于引入了虚拟密度理论和三维时空动力学模型,程序功能更加完善,可以更好地满足快堆工程设计的需求。     

秦山二期堆芯临界计算中核数据的敏感性分析北大核心CSCD

核电软件需要给出计算结果的不确定性,在此基础上才可有效评价核电的安全性。核数据是核电软件堆芯计算不确定性的重要来源之一,而堆芯宏观参数对核数据的敏感性分析是不确定性分析的重要步骤。以秦山二期堆芯为研究对象,对其临界计算结果开展核数据的敏感性分析。首先采用蒙特卡罗程序建立秦山二期首循环计算模型,然后基于中国核数据中心研制的连续能量截面库CENACE V1.0,采用反复裂变几率法计算有效增殖系数对核数据的敏感性系数。通过整理分析秦山二期冷热态、寿期初中末状态的敏感性系数,梳理出核电软件不确定分析中需要关注的重要核素数据。     

低能中子探测的GEANT4模拟研究

研究了GEANT4蒙特卡罗模拟程序在低能中子核反应中应用的可行性, 新版的GEANT(4.9.4版本)升级了老版本在模拟6Li(n, α)3H核反应道的不足, 并且加入了最新截面数据库。 对多个核反应道进行了研究, 模拟结果显示核反应截面、 次级粒子能量和反应的分支比等是正确的; 比较了掺6Li材料热中子探测效率的实验结果与MCNP和GEANT4模拟结果, 它们基本一致。 研究表明, 利用GEANT4研究6Li(n, α)3H是可行的, 这为进一步研究闪烁体中子探测器的位置分辨率模拟提供了有力支持。 The feasible study of Monte Carlo simulation of low energy nuclear reaction was performed based on GEANT4. The reaction channel 6Li(n, α)3H, simulated insufficiently in the old version Geant4, can be given correct results in the new version (version 4.9.4). New cross section library was added into the program. The study of several nuclear reaction channels shows that the cross sections, the secondary particle energies and the branching ratios are consistent with the experimental values. For doped 6Li materials, the comparison of thermal neutrons detection efficiencies of experimental results, MCNP and GEANT4 simulations, shows that the simulations are reasonable. From the studies above, it is feasible to simulate the 6Li(n, α)3H reaction with GEANT4. It will provide helpful information for the further study of the position resolution of scintillation neutron detector.     

Influence of angular momentum on evaporation residue cross section as a probe of nuclear dissipation

By calculating the excess of the evaporation residue cross sections of the ²⁰⁰Pb