Study on Background Count Rate and Counting Efficiency of Plastic Scintillation Microspheres

[Background]: Plastic scintillation microspheres (PSm) are a novel luminescent material with significant potential in the measurement and continuous monitoring of radionuclide activity. [Purpose]: To optimize the application of PSm in radionuclide activity analysis, it is crucial to understand the impact of different measurement conditions on the background count rate and counting efficiency of PSm. [Methods]: The chemiluminescence and photoluminescence of PSm were measured using a Hidex 300SL liquid scintillation counter. The study also investigated the effect of PSm dosage and the type of liquid scintillation vial on the background count rate of PSm. Using 14C as a reference radionuclide, the counting efficiency of PSm under different conditions was determined. Finally, a 20 mL plastic liquid scintillation vial with the lowest detection limit was selected for the activity analysis of 14C solution. [Results]: Weak interference signals from chemiluminescence and photoluminescence were observed when PSm was mixed with water. This interference can be mitigated by keeping the samples in a light-protected environment. The background count rate was positively correlated with the volume of PSm, with larger volumes resulting in higher background counts. The counting efficiency was 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 were minimal. The minimum detectable activity (MDA) of the 20 mL vial was lower. Analysis of 14C solutions in the range of 574.5 to 3825.6Bq·L-1 showed good agreement between measured and expected values. [Conclusions]: The study demonstrates that the background count rate and counting efficiency of plastic scintillation microspheres are influenced by various factors such as sample volume. Under fixed conditions, PSm measurements exhibit good accuracy. PSm shows promising potential in radionuclide analysis.