【作者】 汪量子；

【导师】 王侃； 姚栋；

【作者基本信息】 清华大学 ， 核科学与技术， 2011， 博士

【摘要】 使用易裂变燃料可溶盐的水溶液作为燃料的溶液堆，具备许多区别于固态燃料反应堆的特征。使用溶液堆进行医用同位素生产具有更高的安全性、经济性和提取便利性，然而堆内辐照裂解气体的存在可能限制堆芯功率密度水平，是溶液堆由研究阶段向商业运行阶段转化的主要障碍。气泡行为的模拟是溶液堆计算的重要环节，堆芯尺寸小且不具备重复性构造的复杂几何特征要求物理计算方法具备强大的几何处理能力。本文在计算流体力学（CFD）方法中使用多尺寸组分模型，考虑气泡在堆内的结合与破裂效应，对溶液堆进行两相流模拟，研究气泡在堆内的行为特征，建立了考虑气泡运动因素的溶液堆气泡模型。基于一步法计算思想，使用多群蒙特卡罗方法作为输运计算模块，建立了包含共振处理、燃耗计算、搜索临界棒位、热工水力模型、气泡模型的溶液堆稳态计算模型。在建立瞬态计算模型时，引入改进准静态近似方法以获得较高的计算效率和精度，为了使蒙特卡罗方法能够应用于该方法之中，研究并实现了在蒙特卡罗程序中使用反复裂变几率的统计结果替代共轭通量，作为权重函数计算中子动力学参数的方法；并在多群蒙特卡罗程序MCMG中对源中子抽样机制进行修改，实现了固定源问题的求解功能；最后引入瞬态温度模型和气泡模型，构建了完整的溶液堆瞬态计算模型。基于上述计算模型研制了溶液堆稳态计算程序FMCAHR和瞬态模拟程序TCCAHR，进行数值验证的结果表明：气泡模型计算结果与计算流体力学方法的两相流模拟结果相符，FMCAHR和TCCAHR程序的计算结果与基准结果和溶液堆试验测量结果相符，一步法计算模型的流程简单、近似较少。使用程序对溶液堆物理特性进行研究的结果表明：气泡是影响溶液堆瞬态行为、决定溶液堆固有安全性的主导因素，在传热能力足够的前提下，溶液堆能够达到2kW/L的功率密度水平。通过本文研究，建立了考虑运动因素的溶液堆气泡模型；形成了基于蒙特卡罗方法的一步法溶液堆物理计算模型，为溶液堆计算分析提供了新的手段；对溶液堆物理特性进行了研究，证实了气泡是影响溶液堆瞬态行为的关键因素。更多还原

【Abstract】 AHRs (Aqueous Homogeneous Reactors), which use fissile nuclides’ dissolublesalt’s water solution as fuel, have many different characteristics compared with solidfuel reactors. Producing medical isotopes by AHRs has better safety, economy andextracting convenience than by traditional methods in solid fuel reactors. However,radiolytic gas bubbles’ exist may limit AHRs’ power density, which becomes the mainobstacle in transitioning this technology from research to a commercial industrialenvironment.Simulation of gas bubbles’ behavior is especially important for AHRs’ calculation,the small size and un-repeatable complex geometry requires a stronger geometrytreatment ability of AHRs’ calculation model. Computational Fluid Dynamics method(CFD), along with Multiple Size Group model, and the consideration of bubbles’breakup and coalescence, is used to simulate the two-phase behavior of AHRs. Guidedby gas bubbles’ dynamic behavior studied from the results, gas bubbles’ model of AHRs,which considers bubbles’ movement, is established. Based on the one-step computingtheory, using Monte Carlo method as the transport calculation module, the staticcalculation model of AHRs is established, which contains resonance treatment, burn-upcalculation, critical rod height searching, thermal-hydraulic model and gas bubbles’model. In order to achieve high efficiency and accuracy, improved quasi-staticapproximation method is applied in the transient calculation model. Aiming atintroducing Monte Carlo method into this approximation, a new method of usingiterated fission probability to replace the adjoint flux, and then using it as the weightfunction to compute neutron kinetics parameters, is investigated and carried out inMonte Carlo codes. Also, the sampling mechanism of source neutrons is modified foradding the function of solving fixed-source problems in Multi-group Monte Carlo codeMCMG. Together with the introduction of transient temperature and gas bubbles’ model,the integrated transient calculation model of AHRs is established.According to the calculation model, FMCAHR (Fuel Management Code ofAqueous Homogeneous Reactors) and TCCAHR (Transient Calculation Code ofAqueous Homogeneous Reactors) is developed, verification results show that, theresults of gas bubbles’ model match well with the simulation results of CFD method, calculation results of FMCAHR and TCCAHR keep good consistency with benchmarksand AHRs’ experimental measurement results, the one-step calculation model is simpleand has little approximation. Physics characteristics of AHRs are analyzed usingFMCAHR and TCCAHR, the results show that, gas bubbles are the main issue thatinfluences the transient behavior and brings out the inherent safety of AHRs. As long asthe heat transfer ability is ensured, the power density of AHRs could reach2kW/L.This thesis establishes AHR’s gas bubbles’ model that takes into account ofbubbles’ movement, constructs a one-step calculation model based on Monte Carlomethod, and provides a new implement for the calculation and analysis of AHRs.Preliminary characteristics of AHRs are investigated; the big effect of gas bubbles toAHRs’ transient behavior is validated.更多还原