MC法模拟核部件自发裂变中子活化瞬发γ能谱

在分析中子活化瞬发γ产生机理及瞬发γ射线强度计算方法基础上,提出了应用MCNP程序计算模拟核部件自发裂变中子活化放出瞬发γ能谱的直接模拟与分步模拟方法,对两种方法的计算结果及特点进行了比较分析。计算了模拟核部件核材料自发衰变产生的γ能谱,并与瞬发γ能谱进行了比较分析。本文结果可为核部件认证技术研究提供参考。     

铀水系统核临界安全的蒙特卡罗计算

本工作涉及应用蒙特卡罗程序MCNP4B对铀水系统核临界实验数据进行验证计算和对740L容器取料时漏入CaCl₂盐水后形成的UO₂F₂-CaCl₂水溶液系统的有效增值系数k_eff的模拟计算。计算结果表明，MCNP4B程序对铀水系统核临界安全计算是有效的，漏入盐水后形成的均匀UO₂F₂-CaCl₂水溶液系统是核临界安全的。计算结果为实际生产中的核临界安全性提供了理论依据。      

基于OpenMC的瞬发中子衰减常数计算模块开发与验证

瞬发中子基波衰减常数α可定量描述反应堆内中子随时间的变化,是计算绝对反应性所需的中子动力学参数之一,对次临界（特别是较深次临界）绝对反应性的精确测量具有重要意义。本文在开源程序OpenMC基础上,基于k α迭代方法,以中子径迹长度上的平均时间吸收权重修正作为k α迭代参数因子,在输运过程中对瞬发、缓发中子分别考虑,开发了具有瞬发α本征值问题计算功能的OpenMC PA模块。以Godiva衍生基准题和MUSE 4次临界实验装置为计算对象,对程序计算瞬发α本征值问题能力进行验证。结果表明,该计算模块有优于MCNP4C的计算速度与计算范围,计算值与参考值的相对误差小于05%。OpenMC PA能满足次临界系统瞬发α本征值和中子动力学参数计算需求。     

UF_6转化金属铀核临界安全分析

采用我国现行核临界安全标准及MCNP4C程序,对UF6转化金属铀生产线进行核临界安全分析和评价。选取国际公布的核临界基准实验数据,确认了MCNP4C程序计算分析被评价系统的偏倚和次临界限值。采取偏保守的假设条件,计算分析了镀铜工序正常与可信事故工况下的中子有效增殖因子,并结合核临界安全标准的要求,评价该生产线的安全性。分析结果表明,该生产线次临界控制参数或最大中子有效增殖因子均小于相应次临界限值,处于次临界安全状态。     

铀加工与燃料制造设施公众剂量约束值最优化研究

以国内某一铀加工与燃料制造设施(简称A厂)为例,分析了影响铀加工与燃料制造设施公众剂量约束值最优化的各种影响因素。使用工程判断和多属性效应函数分析方法,综合考虑了关键居民组个人有效剂量、公众集体有效剂量、废物治理费用和公众反应等因素的影响,计算出了不同影响因素权重值情况下铀加工与燃料制造设施公众剂量约束值的最优值,并通过最小二乘法拟合得出剂量约束值最优值与最大效用函数关系曲线。最后采用加权平均计算出铀加工与燃料制造设施公众剂量约束值优化管理目标值的平均值。严格来说,此值的确定依赖于各因素的权重因子,因此这不是"最优解",只能说是一种折衷的"满意解"。     

基于SCALE的RFA改进型燃料组件堆内贮存临界安全分析

RFA改进型燃料组件是西屋公司设计的能应用于大功率先进压水堆的改进型燃料组件。SCALE计算程序是一款在国际上得到广泛认可的综合性建模及模拟程序包,可用于核设计与核安全分析。基于SCALE计算程序,针对大功率先进压水堆的乏燃料贮存水池,建立恰当的计算模型,并选取合理的保守假设,分析乏燃料水池正常贮存及事故工况下的临界安全。计算结果表明一区正常贮存工况keff值为0.901 29,组件跌落事故工况下,有效增值因子为0.907 93。二区正常贮存工况下,计算模型keff值为0.909 98,新燃料组件误插入事故工况keff值为0.924 07。先进压水堆乏燃料贮存水池正常贮存工况及事故工况的有效增值因子均小于0.95,处于次临界状态。该设计模型可确保燃料堆内贮存区域临界状态安全可控。     

MOX燃料贮存水池核临界安全分析

利用MONK程序对MOX热室项目燃料贮存水池进行了核临界安全分析。针对给定的水池尺寸和燃料棒数量，确定燃料以分区方式贮存。选取国际公布的临界基准实验数据，验证并确定MONK程序计算分析类似物料形态时的偏倚和次临界限值，其次进行保守假设，确定贮存水池在正常及事故工况下其中子有效增殖因数，评价贮存水池的安全性。计算结果表明，贮存水池在最危险事故工况下，其最大中子增殖因数小于次临界限值，系统处于临界安全状态。     

乏燃料干式贮存设施临界计算研究

以HI-STORM 100乏燃料干式贮存设施内部装载AFA-3G燃料组件为研究对象,用MCNP(Monte Carlo N Particle Transport Code)4C程序,通过改变贮存设施内外的水密度,采用新燃料假设对不同工况下的临界安全进行研究。结果表明,在正常工况下,keff远低于0.93,是临界安全的。在事故工况下,当水密度大于0.8 g·cm-3时,存在临界安全问题。然后选取适当的核素,通过使用ORIGEN-ARP程序,得到不同燃耗下核素的组成,在同一模型下考虑燃耗信任制,对干式贮存设施的临界安全进行研究。在此基础上,给出了乏燃料干式贮存设施临界安全工作的相关建议。     

中国先进研究堆新燃料组件运输的临界安全分析

在新燃料组件运输过程中,临界安全是重点。使用MCNP程序对中国先进研究堆新燃料组件的运输进行临界安全计算分析,通过选取最不利临界安全的次临界限值、组件模型参数、事故工况来保证计算结果的保守性。结果表明,运输货包的临界安全指数可确定为0。该结果可为中国先进研究堆（CARR）的新燃料组件运输容器的研发提供参考依据。     

UX-30型UF_6运输货包核临界安全分析

利用MONK-9A和MCNP程序对UX-30型UF6运输货包进行了正常与事故工况下的核临界安全分析与评价。首先选取国际公布的临界基准实验数据,验证并确定了MONK-9A和MCNP程序计算分析类似物料形态时的偏倚和次临界限值。其次采取较为包络的临界安全假设条件,计算分析了UX-30型UF6运输货包正常与事故工况下的中子有效增殖因数,评价了运输过程的安全性。计算结果表明,UX-30型UF6运输货包在最严重事故工况下最大的keff小于确定的次临界限值,处于次临界的安全状态。根据临界安全指数的定义,UX-30货包的临界安全指数CSI可定为0。     

球床式高温气冷堆初次临界物理计算的蒙特卡罗方法模型分析

对HTR-10初次临界的几何模型进行了对比和分析,运用基于蒙特卡罗方法的MCNP4B和TRIPOLI-4．3程序描述了高温气冷堆的包缀燃料颗粒在燃料球内的随机分布以及燃料球和石墨球在堆芯的随机混合分布应用TRIPOLI-4．3对HTR-10进行了初次临界物理计算,并且与已有的MCNP4B的计算结果进行了比较结果表明：基于蒙特卡罗方法的MCNP4B和TRIPOLI-4．3程序,采用适当的几何描述方式可以用手球床式高温气冷堆的初次临界堆芯物理计算．     

Criticality safety analysis for a core catcher designed in Korea

Corium is a molten mixture of portions of a reactor core generated by a core melting accident. Corium includes fissionable materials; therefore, a criticality safety analysis must be performed for the core catcher design. This study analyzes the criticality safety of corium arranged in a core catcher developed in Korea. The corium composition was calculated for a 1400 MW_e nuclear power plant. There are several variables involved in the criticality evaluation of corium, thus conservative assumptions were used to reduce the number of variables. A criticality evaluation procedure was employed to assess the operational failure of the core catcher under different accident scenarios. Four kinds of scenarios were selected, and criticality evaluations were pursued for each case. The multiplication factors in each condition were calculated with MCNP5 code. Also, the code bias was calculated with the benchmark problems of 262 LEU experiments to account for the uncertainty of MCNP code. All evaluation results for the assumed scenarios showed that the core catcher satisfies the regulatory guidelines for criticality safety. The calculation results will be used in the design of a core catcher being developed in Korea. It is expected that the data calculated in this study can be used as reference data for criticality safety evaluations of core melting accidents. Also, the procedure for criticality safety evaluation proposed in this study can be utilized to establish regulatory guidelines in Korea.     

最小核临界事故源项分析

文章提出最小核临界事故源项的分析模型，并给出了相关计算方法，利用MCNP程序计算了不同易裂变材料以及不同物料状态下，发生最小核临界事故时的总裂变次数和中子伽马吸收剂量比等源项参数。通过与已发表文献和已有相关数据进行对比，结果符合良好。     

MCNP程序在反应堆临界计算中的应用

用三维的蒙特卡罗程序（MCNP）进行临界计算，着重介绍堆芯和反射层的建模，利用MCNP程序的重复结构功能简化对堆芯的描述，以JRR3为例计算了几个不同棒位于Keff值，计算结果与参值吻合较好，表明MCNP程序能够用于反应堆的临界计算。     

Comparative Studies of ENDF/B-6.8, JEF-2.2 and JENDL-3.2 Data Libraries by Monte Carlo Modeling of High Temperature Reactors on Plutonium Based Fuel Cycles

We performed a numerical comparative analysis of the burnup capability of the Gas Turbine-Modular Helium Reactor (GT-MHR) by the Monte Carlo Continuous Energy Burnup Code (MCB). The MCB code is an extension of MCNP that includes the burnup implementation; it adopts continuous energy cross sections and it evaluates the transmutation trajectories for over 2,400 decaying nuclides. We equipped the MCB code with three different nuclear data libraries: JENDL-3.2, JEF-2.2 and ENDF/B-6.8 processed for temperatures from 300 to 1,800K.

The GT-MHR model studied in this paper is fueled by actinides coming from the Light Water Reactors waste, converted into two different types of fuel: Driver Fuel and Transmutation Fuel. The Driver Fuel supplies the fissile nuclides needed to maintain the criticality of the reactor, whereas the Transmutation Fuel depletes non-fissile isotopes and controls reactivity excess. We set the refueling and shuffling period to one year and the in-core fuel residency time to three years.

The comparative analysis of the MCB code consists of accuracy and precision studies. In the accuracy studies, we performed the burnup calculation with different nuclear data libraries during the year at which the refueling and shuffling schedule set the equilibrium of the fuel composition. In the precision studies, we repeated the same simulations 20 times with a different pseudorandom number stride and the same nuclear data library.     

三维停堆剂量率计算程序研发及其在EAST上的应用

为了精确分析核装置停机后周围空间的三维辐射剂量场分布情况,本文基于停堆剂量计算的严格二步法思想,发展了基于蒙特卡罗输运计算程序MCNP和欧洲活化计算程序FlSPACT的耦合三维停堆剂量计算程序,实现了中子输运、材料活化和光子剂量计算的自动耦合.将该程序初步应用于EAST装置停堆剂量计算,得到了托卡马克装置停堆后周围空间...     

VVER-1000 neutronics calculation with ENDF/B-VII data

The initial release of the ENDF/B-VII nuclear data library is verified for VVER-1000 reactors. For neutronics calculation, the MCNP code based on the Monte-Carlo method is applied. Continuous-energy cross-sections for use with MCNP are calculated with the NJOY code. Isotopics for burned fuel is calculated with the WIMSD code. Calculated criticality, pin-to-pin power distribution, time-dependent critical concentration of soluble boron, worth of the control rods, average fuel assembly powers and time-dependent axial power distribution are compared to the corresponding experimental values for both zero-power VVER-1000 model, created at the LR-0 experimental facility, and the first fuel cycle of a real VVER-1000 reactor. For all of these parameters, neutronics calculation with ENDF/B-VII is in good agreement with the measurement. Moreover, for VVER-1000 neutronics calculation, ENDF/B-VII provides better results than ENDF/B-VI.     

Benchmark Experiment for Radio-Activation of Ex-core Structural Materials using NCA and Analysis with Three-Dimensional Transport Codes

In this study, a radio-activation experiment was conducted using stainless steel outside the active fuel region (active core) in the Toshiba Nuclear Critical Assembly (NCA) in order to verify the homogenization method by simulating the NCA experimental reactor system and understand the effects of this method on the analysis accuracy. In order to validate homogenization method, we simulated the system using the continuous energy Monte Carlo code MCNP, which allows heterogeneously modeling, and examined application of the homogenization method used for modeling commercial boiling water reactors (BWRs) with the TORT code. The calculation results of activation rate obtained by using the MCNP code with either heterogeneous or homogeneous models do not affect the calculation result of activation rate outside the active core. As the homogenization method was validated, the calculation of activation rate using the TORT code was performed with the same homogeneous model as in the MCNP calculation. The results of the activation rate calculation using the TORT code gave values 20 to 30% larger than the calculation results obtained via MCNP for ⁵⁵Mn. This is considered to be caused by thermal energy group structure which is treated as one group.     

基于MELCOR与MCNP程序的安全壳剂量率计算方法

严重事故条件下,评估安全壳内的放射性剂量率水平对核电厂严重事故管理、应急响应等环节具有重要指导意义。本工作利用MELCOR程序模拟严重事故序列,计算不同核素组释放进入安全壳内的质量;利用ORIGEN2程序计算不同核素组的堆芯积存量及核素的γ源强;利用MCNP程序计算每组核素100%释放进入安全壳所产生的剂量率水平;最后根据拟合公式求解安全壳剂量率。中核核电运行管理有限公司30万千瓦机组安全壳剂量率的计算结果说明该方法切实可行。