High-pressure swing system for measurements of radioactive fission gases in air samples

Radionuclides emitted from nuclear reactors, fuel reprocessing facilities a nd nuclear weapons tests are distributed widely in the atmosphere but have very low concentrations. As part of the Comprehensive Test Ban Treaty (CTBT ), identification and verification of the emission of radionuclides from su ch sources are fundamental in maintaining nuclear security. To detect under ground and underwater nuclear weapons tests, only the gaseous components ne ed to be analyzed. Equipment has now been developed that can be used to col lect large volumes of air, separate and concentrate the radioactive gas con stituents, such as xenon and krypton, and measure them quantitatively. By m easuring xenon isotopes with different half-lives, the time since the fissi on event can be determined. Developments in high-pressure (3500 kPa) swing chromatography using molecular sieve adsorbents have provided the means to collect and purify trace quantities of the gases from large volumes of air automatically. New scintillation detectors, together with timing and pulse shaping electronics, have provided the low-background levels essential in i dentifying the gamma ray, X-ray, and electron energy spectra of specific ra dionuclides. System miniaturization and portability with remote control cou ld be designed for a field-deployable production model. (C) 1998 Elsevier S cience B.V. All rights reserved.