Abstract:
Non-destructive analysis(NDA) techniques can be used to ensure that no sensitive nuclear materials(SNM) are being lost or diverted from their defined flows and containments. Rapid measurements of SNM in feed materials, process lines, finished products, scrap and waste, and holdup in the plant are all possible with NDA techniques. With the development of nuclear industry, it has also brought huge challenges to the supervision of nuclear security and nuclear material control. The NDA of pressurized water reactor fuel assemblies is one of the important technologies for nuclear security. The establishment of the NDA for pressurized water reactor requires the possession of corresponding nuclear material standard materials. Therefore, it is necessary to analyze the uranium content and
235U abundance accurately in the uranium dioxide pellets of standard pressurized water reactor components. China North Nuclear Fuel Corpotation prepared comparison samples and conducted a uniformity test on the samples. Through
F test analysis, it was deemed that the samples had good homogeneity. Beijing Research Institute of Uranium Geology(BRIUG) organizes several laboratories to determine the content of uranium in uranium dioxide by potentiometric titration, and the abundance of
235U by TIMS or MC-ICP-MS methods. The samples are sent to different laboratories. Six laboratories conducted comparative analysis of uranium content and
235U abundance. After summarizing and comparing the results, through online SPSS calculations, the small sample data of uranium content and
235U abundance shows a
p-value greater than 0.05, indicating no significant difference. This indicates that the parameter conforms to the normal distribution characteristics. The uncertainty of the comparison data results was evaluated, the uncertainty of sample measurement results refers to ISO guide 35 2017 reference materials: guidance for characterization and assessment of homogeneity and stability, which is mainly composed of three parts: stability uncertainty, homogeneity uncertainty and characterization uncertainty. The uranium content and abundance of
235U in the sample have good homogeneity, and its properties will not change with time. Moreover, the uncertainty caused by the inhomogeneity of the sample has been reflected in the comparison analysis, so in this calculation, the uncertainty components arising from sample inhomogeneities and instabilities are not considered. The average value of uranium mass fraction is 88.00%(
n=6), the relative uncertainty is 0.057%, and the measured average value of
235U abundance is
3.2326%(
n=6), the relative uncertainty is 0.062%. The uranium content and
235U abundance in standard pressurized water reactor components made of uranium dioxide pellets were obtained through comparative analysis, providing base data for subsequent research on non-destructive analysis methods for pressurized water reactors.