Sample treatment techniques for the determination of environmental radiocarbon in a nuclear power station area

Abstract

This report describes the environmental sample treatment techniques for¹⁴C measurement with liquid scintillation counter. The groundwater sample of about 80 liters was collected from well and inorganic carbon was removed by acidification and recirculated gas stripping with the extraction efficiency of more than 98%. The biological samples were freeze-dried and combusted to carbon dioxide in high pressure combustion unit with a combustion efficiency of nearly 99%. The¹⁴CO₂ in the stack effluents was collected by an air bubbler with a collection efficiency of more than 99% for a sampling time of two weeks. Sampling of¹⁴C in reduced form also has been done by passing the gases through a tube furnace with Pt/Al and Pd/Al catalyst. Active and passive sampling methods for atmospheric¹⁴C measurements were compared in detail, and it could be concluded that the uncertainty associated with passive sampling method was quite acceptable for environmental monitoring. The CO₂ trapped in NaOH was precipitated as BaCO₃, and subsequently reconverted to CO₂ for environmental samples and transferred to Carbo-Sorb E^TM for liquid scintillation counting. In case higher precision is the deciding factor, benzene synthesis would be employed with home-made benzene synthesizer.