Plastic scintillation microspheres (PSm) are a novel luminescent material with significant potential in the measurement and continuous monitoring of radionuclide activity.

This study aims to optimize the application of PSm in radionuclide activity analysis by exploring the impact of different measurement conditions on the background count rate and counting efficiency of PSm.

Firstly, PSm samples were prepared by suspension polymerization method, with spherical particles mainly distributed between 95~200 μm in size, and a Hidex 300SL liquid scintillation counter was employed to measure the chemiluminescence and photoluminescence of PSm. Then, the effect of PSm dosage and the type of liquid scintillation vial on the background count rate of PSm were investigated, and the counting efficiency of PSm under different conditions was determined using ¹⁴C as a reference radionuclide. Finally, a 20 mL plastic liquid scintillation vial with the lowest detection limit was selected for the activity analysis of ¹⁴C solution.

Mesaurement results show that weak interference signals from chemiluminescence and photoluminescence are observed when PSm is mixed with water. This interference can be mitigated by keeping the samples in a light-protected environment. The background count rate is positively correlated with the volume of PSm, with larger volumes resulting in higher background counts. The counting efficiency is positively correlated with the height of PSm, with higher heights corresponding to higher counting efficiency. Differences between plastic and glass liquid scintillation vials of comparable specifications are minimal. The minimum detectable activity (MDA) of the 20 mL vial is lower. Analysis of ¹⁴C solutions in the range of 574.5 Bq·L^-1 to 3 825.6 Bq·L^-1 shows good agreement between measured and expected values.

The study demonstrates that the background count rate and counting efficiency of PSm are influenced by various factors such as sample volume. Under fixed conditions, PSm measurements exhibit good accuracy. PSm shows promising potential in radionuclide analysis.