ADS次临界实验装置设计方案验证

根据设计要求．使用MCNP／4C程序计算了多种次临界反应堆均匀化堆芯布置方案的临界问题。确保keff在0．92～1．00之间。为加速器驱动的洁净核能系统(ADS：Accelerator Driven system)的次临界实验装置设计提供了初步数据。     

4 ADS次临界实验装置——启明星1#

加速器驱动的次临界系统（ADS）是嬗变放射性核废物、有效利用核资源及产生核能的装置。该系统包括中能强流质子加速器、外源中子产生器和次临界反应堆。当加速器加速的高能质子轰击重金属靶（如铅）时，与重金属靶核发生散裂反应，一个质子引起的散裂反应可产生几十个中子，用散裂产生的中子作为中子源作用于次临界反应堆上，次临界反应堆发生并维持链式反应，在一定功率下运行。因此，ADS概念一经提出就受到极大关注，被世界核能界公认为是目前解决大量放射性废物，降低深埋储藏风险的最具潜力的工具。     

跳源法在ADS中子学研究中的应用

简要介绍了跳源法在ADS中子学研究中测量次临界度的原理、外源驱动的次临界中子学的实验装置、堆芯布置及中子源驱动系统。主要研究了^252Cf中子源在堆芯不同轴向位置、模拟质子束管和散裂中子靶件处不同缓冲区材料对Keff的影响。实验结果与其它实验方法的结果进行了比较，符合较好。     

ADS次临界反应堆的中子共轭方程

与临界反应堆相比,ADS次临界反应堆的外源中子和裂变中子的空间分布具有严重的不均匀性,对应的中子价值也不同。本工作对次临界反应堆的稳态输运方程作分群扩散近似,得到了多群方程,进一步推导出按堆芯功率归一化的中子共轭方程表达式和与功率相关的中子价值函数表达式,给出了次临界反应堆中子价值的物理意义。由稳态中子共轭方程组出发,给出了两种带外加中子源的次临界反应堆增殖因数的表达式。     

2 ADS次临界中子学研究进展

ADS系统反应堆物理基础研究为中国科技部973项目“加速器驱动核能系统的物理及技术基础研究”的第2课题。五年来，已经完成了计划任务书中规定的所有的项目，包括第1阶段的稳态外源（^252Cf）驱动水堆零功率次临界（东风3号）实验及分析和第2阶段的建立“启明星”实验装置并开展初步实验研究。     

ADS次临界实验装置--启明星1#

文章介绍加速器驱动次临界系统（ADS）中次临界实验装置——启明星1#的设计目的、要求、结构和可开展的工作。启明星1#是由快中子能谱区和热中子能谱区耦合组成的堆芯和由高压倍加器氘-氚反应中子源来驱动的次临界系统。快中子能谱区处在堆芯内部，该区提供快中子谱，还可放大外中子源，以驱动热区；热中子能谱区处在堆芯外部，主要用来能量放大，以维持装置的链式裂变反应。     

4 启明星1#次临界装置上第2阶段实验研究

启明星1#次临界装置建成后，在第1阶段的实验研究即用Am-Be稳态外中子源驱动启明星1#次临界装置，Am-Be稳态外中子源的平均中子能谱约4MV，初步测量了其中子学特性后，又于2005年10月到11月进行了第2阶段的实验，即用高压倍加器产生的脉冲外中子源驱动启明星1#次临界装置。     

ADS原理验证装置快热耦合次临界堆设计

作为加速器驱动洁净核能系统(ADS)原理验证装置"启明星"一号的次临界驱动堆,堆芯采用快-热耦合方式组成,由天然金属铀组成快中子能谱区能有效地嬗变锕系元素(MA),低浓铀元件组成热中子能谱区能有效地嬗变裂变产物(FP).使用MCNP程序对次临界实验装置进行设计计算,确保keff在0.90～1.00之间.     

ADS原理验证装置燃料布置方案

"启明星"的次临界驱动堆是加速器驱动洁净核能系统(Accelerator Driven System,ADS)的原理验证装置,采用快-热耦合的堆芯组成方式,由天然金属铀组成快中子能谱区,低浓铀元件组成热中子能谱区.使用MCNP程序的U卡和Fill卡对次临界实验装置进行设计计算,根据keff在0.90～1.00之间的设计要求,确定了热区的燃料栅格.     

CENDL库中Fe、W评价数据的改进对屏蔽积分实验计算结果的影响

利用中国原子能科学研究院核数据重点实验室中子积分实验装置,分别完成了氘氚中子与不同尺寸Fe、W样品作用的泄漏中子飞行时间谱实验测量。利用MCNP 4C程序开展了泄漏中子飞行时间谱的模拟计算,Fe和W的评价数据分别采用CENDL 32库及CENDL 31库的数据,并将两数据库模拟结果与实验结果进行对比分析,重点分析了CENDL 32库中Fe和W的数据的改进与不足。结果表明：对Fe中子评价数据,CENDL 32库在弹性散射能区、连续能级非弹性散射能区及分立能级非弹性散射能区,模拟结果均与实验结果符合较好,较CENDL 31库有明显改善;对W中子评价数据,CENDL 32库在非弹性散射能区的模拟结果与实验结果符合较好,较CENDL 31库有明显改善,但在弹性散射能区模拟结果高于实验结果,在(n,2n)反应能区模拟结果低于实验结果。CENDL 32库关于天然W的中子评价数据有待进一步改善。     

加速器驱动次临界系统（ADS）与核能可持续发展

描述了ADS系统的主要技术特点和在我国核能可持续发展战略中的作用及地位;介绍了国内外ADS研究的状态和发展趋势;提出了ADS研发必须解决的关键技术问题及解决这些问题的时间表;分析了ADS研发与国内核能相关发展计划的关系;并就我国开展ADS的研发提出了一些建议。     

高能评价核数据处理方法

为满足加速器驱动次临界系统ADS等高能核装置的蒙特卡罗输运计算需求,通过对相关核数据处理模块的改进,建立了一套基于我国自主的群常数制作软件Ruler与国际公认的核数据处理系统NJOY耦合的中高能评价核数据处理方法及程序系统。通过该方法基于日本高能评价核数据库JENDL-HE-2007制作了ACE格式连续点截面库,并通过一系列绘图及简单问题的蒙特卡罗输运计算,验证了该库是完整的、合理的,可用于蒙特卡罗输运计算,证明了Ruler与NJOY功能模块耦合的方法可用于高能评价核数据的处理。     

裂变核全套中子数据评价

裂变核全套中子评价数据对反应堆设计和安全运行、乏燃料少锕系核素嬗变率、嬗变系统及高燃耗反应堆设计提供重要的基础数据。文章对核数据分类、现行主要全套评价数据库及全套核数据评价方法进行阐述,并对234U(n,f)和237Np(n,2n)反应截面的实验数据进行评价。完成的裂变核全套中子数据整体满足用户需求,比原评价结果有较明显改进。     

先进裂变核能的关键核数据测量和CSNS白光中子源

在设计加速器驱动的次临界系统（ADS）、核废料嬗变装置及钍基熔盐堆时亟需一些关键核数据,当前核数据库受实验条件或中子能区的限制,存在核数据精度不高甚至少部分核素数据缺失的情况。本文综述了国内外相关的核数据研究和相应的白光中子源情况。基于中国散裂中子源(CSNS)的反角通道白光中子源实验终端的中子束流具有非常宽的能谱（0.01 eV~200 MeV）和很好的时间特性。模拟得到距靶80 m处的实验终端的中子注量率为9.3×10⁶cm^-2•s^-1,1 eV ~ 1 MeV能量间隔内的中子数占总中子数的53%;同时,加速器运行在双束团模式或单束团模式,时间分辨率均在0.3%～0.9%之间,适合开展核数据测量。     

Neutron Nuclear Data Evaluation of Cesium Isotopes for JENDL-4.0

For the development of JENDL-4.0, neutron nuclear data for fission product nuclides, ^{133,134,135,136,137}Cs, were revised in the incident neutron energy range from 1 eV to 20MeV by using a coupled-channels optical model (OM), and nuclear reaction models. The OM potential parameters were determined for stable ¹³³Cs to reproduce the experimental data of total and elastic scattering cross sections and angular distributions of elastically scattered neutrons. The present results reasonably reproduce measured data for (n; 2n), (n; p), (n; α), and capture reactions on ¹³³Cs. Important differences between the present results and JENDL-3.3 are found for the capture cross sections of ^134,137Cs. The cross section obtained for ¹³⁷Cs was smaller than that in JENDL-3.3. This result makes the transmutation of medium-lived ¹³⁷Cs increasingly difficult. The production probabilities of metastable states for ^134,138Cs via capture reactions on ^133,137Cs are compared with experimental values. The present result for ^134m Cs production is marginally consistent with measured data. However, a large discrepancy is recognized for ^138m Cs production. The γ-ray emission data were evaluated with available measurements, and newly compiled in JENDL-4.0. Maxwellian-averaged capture cross sections were calculated in the energy range from 1 to 103 keV, and are compared with other derived data.     

Evaluation of Neutron Nuclear Data for Sodium-23

Neutron nuclear data of ²³Na have been evaluated in the neutron energy region up to 20 MeV. Evaluated are the elastic and inelastic scattering, capture, (n, 2n), (n, p), (n, α), (n, np), (n, nα) reaction and γ-ray production cross sections, and the angular and energy distributions of neutrons and γ-rays. The evaluation is mainly based on nuclear model calculations. The pre-equilibrium and direct-reaction processes were taken into account in addition to the compound process. The evaluated data have been compiled into the latest version of JENDL, JENDL-3.3.     

New Evaluation of Neutron Nuclear Data for Zinc Isotopes

New evaluation of neutron-induced nuclear data for five stable isotopes of zinc (mass numbers A = 64, 66, 67, 68, and 70) was consistently carried out in the incident neutron energy range from 10^?5 eV up to 20MeV. In the low energy region up to about 100keV, the resonance parameters were evaluated by taking account of the available measured data. In the fast neutron region, the comprehensive calculations with nuclear reaction models, in which compound, preequilibrium, and direct processes are taken into account, were performed to estimate cross sections for various reactions and double differential cross sections of emitted neutrons and γ-rays. The comparisons of the evaluated cross sections with the experimental data and existing evaluated nuclear data libraries are made and show a good agreement with the measurements.     

Test of235U Covariance Data with Nuclear Data Adjustment BenchmarkWU Haicheng

Nuclear data covariances are important input data for quantificational assessment of nuclear facility design uncertainty and nuclear data adjustment (NDA), which give direct impact on estimated uncertainties and results of NDA. To test the rationality of the newly evaluated nuclear reaction cross sections covariance in smooth region for²³⁵U which is generated based on the analysis of source of experiments uncertainties and linear least-square method, the data were tested with the NDA benchmark exercises recommended by the OECD/NEA WPEC/SG33. The input data of the NDA generated from JENDL-4.0 library were updated with the cross sections and covariances of ²³⁵U fission, capture and inelastic scattering reactions from²³⁵U cov, and used in NDA calculation. The new results were compared with the original JENDL-4.0 ones. The test results show that the covariance data from²³⁵U cov are unreasonable. Too large uncertainties around threshold energy of inelastic scattering reaction were found. The uncertainties of fission and capture cross sections in smooth region are too small to be supported by NDA results.     

核数据处理程序NECP-Atlas的开发与验证

本文开发了自主化的核数据处理程序NECP-Atlas,该程序将不同的核数据处理功能封装为不同的程序模块,可将评价核数据经过共振重构及线性化、多普勒展宽计算、不可分辨共振区处理、热中子散射计算、多群截面计算等过程,处理为WIMS-D/E格式多群数据库。采用WLUP（WIMSD library update project）基准题、国际临界安全基准题ICSBEP（international criticality safety benchmark evaluation project）等对NECP-Atlas加工产生的核数据进行验证,结果显示NECP-Atlas和NJOY-2016程序精度相当。