Design and preliminary test of tritiated water online detector system based on plastic scintillators

In this study, an online detector system based on plastic scintillators is designed to monitor the activity of tritiated water in the liquid effluents of nuclear power plants. The feasibility of the detector is verified via simulation on Geant4, and the optimal detector structure size is determined. A back-end electronics system is designed, and an experimental measurement platform for β-rays based on a 40 KCl solution is constructed. Thirteen 40 KCl solutions with different activities ranging from 10 to 4500 Bq/L are measured, and 1300 V is determined as the optimal operating high voltage of the photomultiplier tubes. A linear fit is performed in 10-min counts, and the maximum linear goodness of fit ( R 2 ) achieved is 0.9992. Long-term stability measurements are performed for two detectors, one filled with air and the other with a 40 KCl solution exhibiting an activity of 2000 Bq/L. The relative deviation of the counts of the detector system every 10 min is 0.998% when the 40 KCl solution is used, and the maximum Gaussian R 2 of the counts is 0.9849.