基于RMC的蒙特卡罗燃耗计算氙振荡抑制方法研究
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摘要
蒙特卡罗燃耗计算模型为中子输运弱耦合系统时,计算结果会出现数值振荡,从而引入较大误差,甚至导致计算终止。蒙卡燃耗计算中出现的数值振荡主要由堆内的裂变毒物氙驱动,所以如何有效抑制氙振荡是蒙卡燃耗计算研究的内容之一。强制平衡氙方法在各燃耗步功率保持恒定时有很好的抑制效果,但在小步长变功率燃耗计算时,所得的计算结果存在显著偏差。目前,国际主流的反应堆基准题提出了变功率燃耗计算的需求,为抑制小步长变功率燃耗计算的氙振荡,在堆用蒙卡程序RMC中开发了通用平衡氙方法。本文介绍RMC中主要采用的平衡氙方法,包括强制平衡氙方法和通用平衡氙方法。对数值验证的计算结果进行分析和比较,结果表明通用平衡氙方法能有效抑制定功率及小步长变功率蒙特卡罗燃耗计算的氙振荡现象。
Monte Carlo burnup calculation suffers from numerical xenon oscillation when its model is huge geometry,refers as weakly coupled neutron transport system.Numerical xenon oscillation brings in error,even aborts burnup calculation.How to effectively prevent such oscillation is a significant topic in Monte Carlo burnup calculation.Forced equilibrium xenon method is effective when the power density used in each burnup step of the calculation keeps constant.This method has been researched and used in RMC,furthermore,some improvement has been complemented to extend range of burnup steps.Some popular international benchmarks,such as BEAVRS,VERA,require simulating burnup problem with variable power history.However,forced equilibrium xenon method inevitably brings error when power density changes by relative small burnup step.To research and develop advanced Monte Carlo simulating ability including high performance of burnup calculation,general equilibrium xenon method based on forced equilibrium method is researched and integrated to RMC.Numerical calculation result verifies that the general equilibrium xenon method is capable of effectively preventing xenon oscillation in Monte Carlo burnup calculation with constant or variable power density in each step.
Monte Carlo burnup calculation suffers from numerical xenon oscillation when its model is huge geometry,refers as weakly coupled neutron transport system.Numerical xenon oscillation brings in error,even aborts burnup calculation.How to effectively prevent such oscillation is a significant topic in Monte Carlo burnup calculation.Forced equilibrium xenon method is effective when the power density used in each burnup step of the calculation keeps constant.This method has been researched and used in RMC,furthermore,some improvement has been complemented to extend range of burnup steps.Some popular international benchmarks,such as BEAVRS,VERA,require simulating burnup problem with variable power history.However,forced equilibrium xenon method inevitably brings error when power density changes by relative small burnup step.To research and develop advanced Monte Carlo simulating ability including high performance of burnup calculation,general equilibrium xenon method based on forced equilibrium method is researched and integrated to RMC.Numerical calculation result verifies that the general equilibrium xenon method is capable of effectively preventing xenon oscillation in Monte Carlo burnup calculation with constant or variable power density in each step.
引文
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[4]Chen Zonghuan.Research of power correction methods in monte carlo burnup calculations based on equilibrium xenon[D].Beingjing:Department of Engineering Physics,Tsinghua University,2015.
[5]Wang K,Z Li,D She,et al.RMC–A Monte Carlo code for reactor core analysis[J].Annals of Nuclear Energy,2015,82:121-129.
[6]Horelik N,Herman B,Forget B,et al.Benchmark for evaluation and validation of reactor simulations(BEAVRS),v1.0.1[C].Proc.Int.Conf.Mathematics and Computational Methods Applied to Nuc.Sci.&Eng.2013.
[7]Godfrey A T.VERA core physics benchmark progression problem specifications[J].Consortium for Advanced Simulation of LWRs,2014.