Analysis of Krypton-85 and Krypton-81 in a Few Liters of Air

Abstract

Long-lived radioactive krypton isotopes, (81)Kr (t1/2 = 229,000 year) and (85)Kr (t1/2 = 10.76 year), are ideal tracers. (81)Kr is cosmogenic and can be used for dating groundwater beyond the (14)C age. (85)Kr is a fission product and can be applied in atmospheric studies, nuclear safety inspections, and dating young groundwater. It has long been a challenge to analyze radio-krypton in small samples, in which the total number of such isotopes can be as low as 1 × 10(5). This work presents a system developed to analyze (81)Kr and (85)Kr from a few liters of air samples. A separation system based on cryogenic distillation and gas chromatographic separation is used to extract krypton gas with an efficiency of over 90% from air samples of 1-50 L. (85)Kr/Kr and (81)Kr/Kr ratios in krypton gases are determined from single-atom counting using a laser-based atom trap. In order to test the performance of the system, we have analyzed various samples collected from ambient air and extracted from groundwater, with a minimum size of 1 L. The system can be applied to analyze (81)Kr and (85)Kr in environmental samples including air, groundwater, and ices.

81Kr Dating at the Guliya Ice Cap, Tibetan Plateau

“…The extracted gas from the ice samples was sent to the University of Science and Technology of China (USTC) for krypton purification and for ATTA analysis of both 81 Kr and 85 Kr. Krypton is separated from the extracted gas using a purification system based on titanium gettering and gas chromatography (Tu et al, ), typically yielding krypton purities and recoveries both higher than 90%.…”

“…Krypton is separated from the extracted gas using a purification system based on titanium gettering and gas chromatography (Tu et al, 2014), typically yielding krypton purities and recoveries both higher than 90%. Krypton is separated from the extracted gas using a purification system based on titanium gettering and gas chromatography (Tu et al, 2014), typically yielding krypton purities and recoveries both higher than 90%.…”

Laser-Based Metastable Krypton Generation

“…Metastable noble gas atoms [1] have found wide use since the advent of laser manipulation of atoms, with diverse applications including atom lithography [2,3], rare isotope detection [4][5][6], Bose-Einstein condensation [7], optically pumped rare gas lasers [8], high resolution spectroscopy [9], and high precision fundamental physics experiments [10,11]. Metastable krypton (Kr * ) itself finds use in krypton tagging velocimetry [12] and for radiokrypton dating [13][14][15]. These applications all require an experimental step to prepare the target into the relevant high energy (10-20 eV) metastable state.…”

81Kr dating – A tool for finding and studying paleogroundwater

“…Samples obtained in the field need to be pre-treated before analysis with ATTA to separate the Kr from bulk gas (N2, O2, Ar, etc). Pre-treatment requires about 1.5-2 hours and is quite labor intensive [17]. To keep up with the increasing demand, a fully automated sample pre-treatment system was developed at USTC.…”