Investigation of fast screening LSC method for monitoring ¹⁴C activity in wastewater samples

Abstract

© 2018 Elsevier Ltd This paper explores the possibility of a direct measurement of 14C activity concentration in wastewater without chemical pretreatment of samples, which would provide the advantages such as rapidity, low-cost, and simplicity of radioanalysis that is desirable in the case of nuclear emergencies. A method via Liquid Scintillation Counting (LSC) technique has been implemented and optimized. The method assumes mixing of the water sample with a scintillation cocktail (Permafluor E+ and Ultima Gold AB cocktails were tested). Measurements were performed on Ultra Low Level Liquid Scintillation Spectrometer Wallac 1220 Quantulus. Optimization of the method included optimal water:cocktail volume ratio, optimal counting window selection, PAC (Pulse Amplitude Comparator) parameter adjustment, based on the highest FOM (Figure of Merit) value achieved, as well as detection efficiency and detection limit evaluation. The main problem in such an approach, interference with other beta emitters that are often present in wastewater samples, has been discussed. The possibility to eliminate low-energy counts that would be generated from 3H, and to estimate the contribution of other high-energy beta emitters to obtained results of 14C content is presented as well. Method's constraints, its accuracy, and precision have been considered from the obtained results of measurements of wastewater samples. Its application is limited only to 14C screening of samples with much higher 14C activities than those of the environmental (surface and ground) waters. Presented results could be used as guiding principles of development, optimization, and implementation of the fast 14C screening method in other laboratories.