Preparation of ¹⁵¹Sm calibration standards for AMS measurement

Abstract Background: The long-lived fission product ¹⁵¹Sm plays an important role in environmental science, life science, nuclear data, etc. It is interesting to establish a high precise and sensitivity measurement method with Accelerator Mass Spectra (AMS) and develop a series of standards of ¹⁵¹Sm. Purpose: The aim is to develop a series of laboratory reference standards for ¹⁵¹Sm AMS measurements. Methods: The long-lived radioactive nuclide ¹⁵¹Sm was produced via neutron capture reaction of ¹⁵⁰Sm by the irradiation of 52.6-mg Sm₂O₃ (with ¹⁵⁰Sm enriched to 87.34%) in the Heavy Water Research Reactor (HWRR) at China Institute of Atomic Energy (CIAE). The ¹⁵¹Sm/¹⁵⁰Sm ratio in the irradiated Sm₂O₃ sample was measured with Thermal Ionization Mass Spectrometry (TIMS) at the Nuclear Power Institute of China (NPIC). This standard ¹⁵¹Sm sample was then diluted with the enriched ¹⁵⁴Sm₂O₃ (¹⁵⁴Sm is enriched to 98.61%) to obtain three other standards. Results: The ¹⁵¹Sm/¹⁵⁰Sm ratio in the irradiated Sm₂O₃ sample is 3.75 × 10^-3 (the relative standard deviation is 0.06%) measured with TIMS. Three standards with ¹⁵¹Sm/¹⁵⁴Sm ratios of (9.25 ± 0.08) × 10^-7, (8.87 ± 0.08) ×10^-8 and (8.08 ± 0.08) × 10^-9, respectively, were prepared for the calibration in AMS measurement of ¹⁵¹Sm. The concentrations of Sm in standard solution (I) and diluent solution were measured using isotopic dilution mass spectrometry. Conclusion: The measurement method of TIMS for isotope ratio of ¹⁵¹Sm was established. A series of standards was prepared for the calibration in AMS measurement of ¹⁵¹Sm. (authors)