Chapter 2 - Environmental liquid scintillation analysis

Abstract

Liquid scintillation counting (LSC) is a major method for the measurement of beta-emitting and some alpha-emitters. It has been applied in many aspects such as the monitoring of environmental radioactivity, the behavior of radionuclides in the environment, and the characterization of nuclear waste for the decommissioning of nuclear facilities. Radionuclides are also widely applied to the investigation of environmental processes. However, the level of radionuclides in the environment is normally very low, and the resolution of LSC alone is not sufficiently high to identify and quantitatively measure different radionuclides. Low background LSC and chemical separation and purification are needed. This chapter aims to present the principles of LSC measurement techniques for the above purposes and focus on the practical issues in the LSC determination of environmental radionuclides, as well as the status of the present research progress in these aspects. The principles of low-level counting using LSC including the methods for reducing the background in the LSC instrument and practical issues in sample preparation are presented. The principles and applications for the measurement of alpha-emitters using LSC with the alpha/beta discrimination features are presented. The main application of triple-to-double coincidence ratio–based LSC in normal and Cerenkov counting models are also described. Most of the effort of this chapter focuses on the application of LSC in the determination of different anthropogenic and naturally occurring radionuclides, including tritium, 14C, 55Fe, 63Ni, 89,90Sr, 90Y, 99Tc, 241Pu, 36Cl, 41Ca, 129I, 210Po, 210Pb, isotopes of uranium, thorium, radium, and radon. Besides the LSC measurement methods, the detailed and practical chemical separation of these radionuclides from different sample matrices, as well as the sample preparation methods for LSC measurement are discussed based on the open publications and the experiences of the authors.