加速器束流瞬变ADS次临界堆中子动力学时空演化特性与响应机理研究

Impact to the subcritical reactor induced by beam transients is a key issue to ADS reliable operation, the intensive external neutron source with high energy and the reactor in deep subcritical present new challenges to the analysis methods on neutron kinetics. .To study the kinetic mechanism of the subcritical reactor under beam transients with large energy span and high heterogeneity of time-space-energy, this project will develop a high energy multi-group constant library , broadening the energy region of ADS Quasi-static kinetics to GeV; Under multi-group scheme, the neutron flux density of ADS steady state, fundamental and harmonics functions of time eigenvalue problem will be calculated to generate the time-space multi-modes few-group core constants, overcoming the shortage of the single few-group constant generated by “two-steps” method, which can not consider the neutron flux density and spectrum shifting; Based on the benchmark results given by simulated experiment, analysis will be performed and new analyze method of ADS subcritical reactor dynamic characteristics with multi-modes few-group constant self-adapting and optimized weight function will be established. The dynamic characteristics with various sub-criticalities and beam transients will be investigated to reveal the response mechanism of ADS subcritical reactor caused by “spatial effect”, “spectrum effect” and synergistic effect of “external neutron source and sub-criticalities”..This research will be meaningful to the development of neutron kinetics theory and promote ADS R&D activities.

束流瞬变对次临界堆的冲击是影响ADS系统可靠运行的关键问题之一，高能强外源与深次临界度特性对中子动力学分析方法提出了新挑战。.为阐明大跨度能谱、强“时间-空间-能量”非均匀性对束流瞬变ADS次临界堆中子动力学作用机制，本项目将研制GeV量级多群数据库，拓宽ADS 准静态中子动力学研究能量范围； 开展ADS次临界堆稳态、时间本征值基/谐波中子通量多群计算，产生束流瞬变时-空相关“多模式”堆芯少群常数库，解决“两步法”少群常数无法描述中子通量和能谱随时空变化的缺陷；以模拟实验为基准，分析建立“多模式”少群常数自适应调用、权重函数最优化的束流瞬变ADS次临界堆动态特性分析方法；揭示不同次临界度和束流瞬变工况ADS次临界堆中子学参数时-空演化行为，探索空间效应、能谱效应、外源-次临界度协同作用下束流瞬变ADS 次临界堆动态特性响应机理。.本项目对完善中子动力学理论与促进ADS研发具有重要意义。

加速器驱动次临界系统（ADS）是嬗变高放长寿命核废物的强有力工具，束流瞬变对次临界堆的冲击是影响ADS系统可靠运行的关键问题之一，高能强外源与深次临界度特性对中子动力学分析方法提出了新挑战。. 为阐明大跨度能谱、强“时间-空间-能量”非均匀性对束流瞬变ADS次临界堆中子动力学作用机制，本研究利用现有高能评价数据库JENDL-HE-2007，分析ADS次临界堆能谱特点，研制了ADS次临界堆用大跨度能谱高能多群数据库ADS-HE-MATXS，拓宽ADS准静态中子动力学研究能量范围。. 本研究研制了高能连续能量截面库ADS-HE-ACE，开展ADS次临界堆静态蒙卡计算。通过调节堆芯裂变中子产生截面υΣf，利用高能连续能量截面库ADS-HE-ACE，由蒙卡输运程序MCNPX计算得到不同束流瞬变工况和次临界度下的ADS 次临界堆动态特性，动态结果用于准静态近似结果的基准。. 本研究开展了ADS 次临界堆基准模型在散裂中子源驱动下的稳态多群输运计算，归并参考三维四群ADS堆芯的均匀化少群常数产生有束流工况仅与空间相关的二群堆芯少群常数；ADS次临界堆α本征值问题基波/谐波宽群中子通量计算，归并产生无束流工况随时-空变化的堆芯少群常数；链接产生可描述任意束流瞬变工况的“多模式”堆芯少群常数库，解决“两步法”少群常数无法描述中子通量和能谱随时空变化的缺陷。. 本研究建立了束流瞬变ADS次临界堆中子动力学准静态模型的幅度函数和形状函数方程和ADS次临界堆keff本征值共轭方程、α本征值共轭方程、散裂中子源驱动ADS次临界堆稳态共轭方程，编制了对应的求解程序；分别采用“两步法”堆芯少群常数和“多模式”堆芯少群常数，开展不同权重函数下的束流瞬变ADS 次临界堆动态特性模拟，并与直接求解结果比较，建立“多模式”堆芯少群常数“自适应调用”、权重函数最优化的束流瞬变ADS次临界堆动态特性分析程序；分析 ADS次临界堆的中子通量、中子能谱、动力学参数在不同束流瞬变工况和次临界度下的时-空演化特性。结果表明，对于有束流工况，采用散裂中子源驱动ADS次临界堆稳态模式；对于无束流工况，采用瞬发α本征值模式，可以有较高的计算精度。. 本研究对完善中子动力学理论与促进ADS研发具有重要意义。