Shuffler中子质询系统核材料质量测量的基体校正新方法

Background]Active neutron interrogation (ANI) measurement systems can quantify the fissile mass of special nuclear materials (SNMs) using neutrons and are widely used in nuclear safeguard fields. However, the hydrogen-containing matrix in the waste drum reduces the signal of delayed neutrons and limits the fissile mass measurement precision of the ANI system. [Purpose]It is essential to ensure that the fissile mass evaluation of the SNM is independent of matrix material and to improve the assay performance of the ANI system in nuclear safeguard measurements. [Methods] Therefore, based on the flux monitor response, a new matrix correction method was developed on the basis of traditional correction methods in this work. [Results]It turned out that the effect of various hydrogen densities on the delayed neutron count rate differs. For U3O8 materials with different enrichment and distribution, matrix effect may result in an overestimation of up to ~7 times in the observed mass of 235U. For U3O8 materials with different 235U enrichments and distribution states, both the traditional correction method and the new correction method can effectively reduce the influence of the matrix material on the measurement of SNM mass. But compared with the traditional method, the new method can achieve better correction results. For the case where U3O8 material is located in the center of the matrix, the average relative deviation of 235U mass obtained by the new correction method is 13.6%, while for the case where U3O8 material homogeneous dispersed throughout the matrix, the average relative deviation of 235U mass obtained by the new correction method is 7.78%. [Conclusions]These results confirm the effective performance and practicality of the new correction method.