Comparison of AMS, TIMS and SIMS techniques for determining uranium isotope ratios in individual particles

Abstract

The determination of isotope ratios in individual uranium particles is very important for nuclear safeguards. In this work, accelerator mass spectrometry (AMS), thermal ionization mass spectrometry (TIMS) and secondary ion mass spectrometry (SIMS) were applied to isotope ratio analysis of individual uranium particles and compared in terms of background, measurement accuracy and efficiency. Several individual uranium particles (1−7 μm) from certified reference materials were used as samples. The results show that the average values of blank counting rate of ²³⁵U for AMS, FT-TIMS (FT: fission track), SEM-TIMS (SEM: scanning electron microscope) and SIMS were 7.3, 7.8, 2.7 and 2.2 cps, respectively. The relative error of ²³⁴U/²³⁵U and ²³⁴U/²³⁶U isotope ratios of the particles from U200 for AMS were within 10% and 20%, whereas the results of FT-TIMS and SIMS were within 5% and 10%, respectively. The relative error and external precision of ²³⁴U/²³⁸U and ²³⁵U/²³⁸U of the particles from U850 for the method of AMS, SEM-TIMS and SIMS were within 10% and 5%, respectively. For ²³⁶U/²³⁸U, the average values of the relative error and external precision measured by AMS were within 5%, which measured by SEM-TIMS and SIMS were all within 10%. AMS has advantages in measuring ²³⁶U/²³⁸U. The measurement time of AMS and SEM-TIMS was shorter than that of FT-TIMS and longer than that of SIMS. It is considered that AMS and SEM-TIMS have a certain development prospect, and it is necessary to research deeply.