Background: Determination of the uranium isotope abundance ratio of fuel pins is a significant stage for the quality control in safe operations of reactor. Purpose: The aim is to establish a method to examine the 235U abundance of fuel rod with fast neutron as an excitation source. Methods: Taking the fission-yield ratios of / and / as the subjects of research

the relation curves between the average yield ratios and the 235U isotopic abundance as well as the expressions

in which the average yield ratio ( ) is a function of the 235U isotopic abundance (H0)

were obtained and presented based on the previous studies. Results: In order to testify the accuracy of the method

the simulation sample of 72.2% is measured by working curve

and RSD is less than 2%. Within the limit of error

the results of sample analysis are in correspondence with those of passive gamma ray method. Conclusion: All of these results indicate that the method is feasible to determine the 235U abundance of fuel rod.Cited