基于反应率预测的预估校正方法研究

Research on Predictor-Corrector Method Based on Prediction of Reaction Rates

传统预估校正方法通过平均预估步与校正步的核素组分修正燃耗计算结果,要求在每个燃耗步上进行2次中子学计算。为了降低输运燃耗耦合计算的时间,本研究对传统预估校正方法进行了分析,并开展了基于反应率预测的预估校正方法研究,该方法利用传统预估校正方法中预估步与校正步多群中子能谱差异随燃耗光滑变化的特性,通过拉格朗日插值方法对区域和燃耗时间相关的中子能谱偏差随燃耗时间的变化特征进行描述,获得解析的插值公式,在保证预估步计算次数不变的情况下,直接对部分校正步的反应率进行预测,避免该部分校正步的中子学计算;本研究以传统预估校正方法为参考,通过VERA燃耗基准题和JAEA燃耗基准题对提出的基于反应率预测的预估校正方法进行了验证。数值结果表明:基于反应率预测的预估校正方法可在保证棒功率分布与主要核素组分精度基础上,减少约20%的中子学计算时间。因此,本研究建立的基于反应率预测的预估校正方法能够用于高效的输运燃耗耦合计算。

Traditional predictor-corrector method revises the burnup calculation results by means of the nuclide inventory of the average predictor step and the corrector step,two neutronics calculations are required at each burn-up step.In order to reduce the time of transport-burnup coupling calculation,the traditional predictor-corrector method is analyzed in this work and the predictor-corrector method based on the prediction of the reaction rates is proposed in this work.This method makes use of the characteristics of the smooth variation of the multi-group neutron spectrum difference between the predictor step and the correction step with burnup in the traditional predictor-corrector method,Lagrangian interpolation method is used to describe the variation characteristics of regional and burnup time related neutron spectrum deviation with burnup time,and analytical interpolation formula is obtained.Under the condition that the calculation times of the predictor steps remain unchanged,the reaction rate of some corrector steps is predicted directly so as to avoid the neutronics calculation of such corrector steps.This study takes the traditional predictor-corrector method as reference,and verifies the proposed predictor-corrector method based on reaction rate prediction through VERA and JAEA burnup benchmark tasks.The numerical results show that the predictor-corrector method based on reaction rate prediction can reduce the neutronics calculation time by about 20%on the basis of ensuring the rod power distribution and the accuracy of the main nuclide components.Therefore,the predictor-corrector method based on reaction rate prediction established in this study can be used for efficient transport-burnup coupling calculation.