The substitutability of liquid scintillation cocktail for CaF2(Eu) powder in low-level tritiated water measurement

Abstract

The liquid scintillation counting (LSC) is an established method for direct quantitative measurement of tritiated water, but the generated radiotoxic waste, its storage, handling and proper disposal is the major concern arising from using scintillation cocktail. In our work, CaF2(Eu) was chosen as the scintillation material to substitute scintillation cocktail in low-level tritiated water measurement. In order to find out the ideal vial type, grain size of powders and CaF2(Eu) powders quantity, three groups of 6 and 20 ml scintillation vials filled with different CaF2(Eu) powders were prepared. Using polyethylene vial, which is much smaller than the glass vial, significantly increased the detection efficiency. The highest detection efficiency was achieved by using polyethylene vial and 4 g S sample (average grain sizes: 8.355 μm). In addition, the polyethylene vials with 4 g S sample inside were most sensitive and had the best linear relation between tritium concentration and count rate. Under this condition, the detection limit can be as low as about 13 Bq/mL. The CaF2(Eu) powder can be re-used after a simple treatment. What's more, it is nontoxic as well as easy to store and disposal. These make it advantageous compared with traditional scintillation cocktail. With these results, the replacement of the scintillation cocktail with CaF2(Eu) powder in low-level tritiated water measurements is promising.