Pulse time interval analysis (TIA) combined with liquid scintillation counting for the determination of environmental α-nuclides: Preparation and utilization of²²⁵Ra as a yield tracer

Abstract

Time interval analysis (TIA), which has been verified to be suitable for the selective extraction of correlated successive α-decay events within a liquid scintillator, was further developed by combining pulse shape discrimination technique and simple chemical analysis. A β-emitter nuclide,²²⁵Ra, which is suitable for the use as a yield tracer belonging to Np-decay series, was also found to be detectable by the TIA-method after a certain standing period when the radium-extractant (RADAEX) was added small amounts of HDEHP [di (2-ethylhexyl) phosphoric acid], which was proved to keep the equilibrium state between Ra and its descendants. The present counting system (TIA analysis incorporated α-LSC/PSD) has been verified to be applicable to the simultaneous determination of three (including Th, Ac, and Np) decay series, if the chemical purification of radium fraction was applied to the environmental samples using an extractive scintillator in addition to utilization of an α-peak itself at lowest energy for the determination of²²⁶Ra in uranium decay series. This radioanalytical method was practically applied to the determination of natural radionuclides belonging to three decay series in environmental samples and compared to the alpha-spectrometric results using a Si-surface barrier detector (SSB).