一种测量废包壳中U、Pu含量的方法研究

乏燃料组件在后处理厂经过剪切、浸取后的残留物被称为废包壳,测量其中含有的U、Pu质量将作为判断乏燃料溶解工艺水平的一个重要参考依据,或者作为是否需要对废包壳进行再次溶解操作的判断标准。本文在分析废包壳放射性组成情况的基础上,鉴于通过直接测量U、Pu特征粒子分析其质量存在困难,提出一种通过间接方式测量废包壳中残留U、Pu含量的方法,并开展初步的研究工作。此方法设计了一套基于3He正比计数管的测量装置,采用中子符合法测量分析废包壳中244 Cm的含量,并针对测量对象的放射性分布不均匀性,开展测量装置内部空间探测效率分布模拟计算,给出测量的极限误差分析;建立乏燃料组件核素组成信息模拟计算程序,分析计算日本同类型乏燃料组件的关注核素含量,并比对此组件的破坏性分析(DA)结果,给出计算结果的不确定度,并通过上述程序计算得到废包壳对应乏燃料组件中的244 Cm/U(Pu)值。结合测量数据和计算数据,可推导出废包壳中的U、Pu质量。此外,本文还分析这种测量分析方法的误差构成,评估最终分析结果不确定度,为工艺判断提供数据支持,同时指出下一步研究工作的方向。

The Measurement Method of the U and Pu Mass in the Leached Hull

The residue of spent fuel assembly after shearing and leaching in the reprocessing plant is called Leached Hull.The measurement of the U and Pu content will be an important reference for judging the level of spent fuel dissolution process,or as a judgment standard for whether it is necessary to re-dissolve the Leached Hull.In this paper,based on the analysis of the radioactive composition of the Leached Hull,and in view of the difficulty in analyzing the quality of U and Pu in the Leached Hull by directly by measuring the U and Pu characteristic particles,a method of indirectly measuring the residual U and Pu content in the Leached Hull is proposed,and the preliminary research work is carried out.In this method,a measuring device based on 3He proportional counter is designed.The content of 244 Cm in the Leached Hull is measured and analyzed by neutron coincidence method.Aiming at the possibility of inhomogeneous distribution of radioactivity in the measured object,the simulation calculation of spatial detection efficiency distribution in the measuring device is carried out,and the limit error analysis of measurement is given.The nuclide composition information simulator of spent fuel assembly is established in the calculation program,the concerned nuclide content of the same type of spent fuel assembly in Japan is analyzed and calculated,then compared with the destructive analysis(DA)analysis result of this assembly,the uncertainty of the calculation result is given,and the 244 Cm/U(Pu)value in the spent fuel assembly corresponding to the Leached Hull is calculated by the above program.Combined with the measured data and calculated data,the mass of U and Pu in the Leached Hull can be deduced.In addition,this paper also analyzes the error composition of this measurement analysis method,evaluates the uncertainty of the final analysis results to meet the needs of process judgment,and points out the direction of the next research work.