Online monitoring of atmospheric krypton-85 with hourly time resolution

Abstract

⁸⁵Kr is a major radioactive byproduct released during nuclear fuel reprocessing and an important atmospheric indicator for nuclear safety and environmental monitoring. In this work, we report on online monitoring of atmospheric ⁸⁵Kr activities with time resolution of 1.5 hours. An automated Kr purification system and an atom trap based ⁸⁵Kr measurement system work synchronously in the experiment. The Kr purification system features temperature-controlled cryogenic distillation and gas chromatography, which allows direct sampling of ambient air and continuous operation. The separated Kr is fed into an atom trap capable of measuring the abundance of ⁸⁵Kr with micro-L size Kr samples. The sample consumption is 3 L STP of air per measurement with a 1.5 hour processing time. Compared to the conventional monitoring method based on proportional counting, both the measurement time and sample size (10 m³ and 1 week) are reduced by several orders of magnitude. The ⁸⁵Kr analysis technology demonstrated in this work allows analysis of atmospheric ⁸⁵Kr activities with hourly resolution, enabling applications such as online monitoring of nuclear fuel reprocessing plants and tracing of atmospheric circulation patterns.