Radon release characteristics of autunite under coupled environmental temperature and humidity conditions.

Autunite is a representative secondary uranium ore. Because of its high uranium content and low cost, autunite has potential as an inexpensive and stable radon source. However, the radon-release behavior of autunite remains poorly characterized. A closed-loop radon-accumulation system based on a RAD7 detector was developed in this study. Nine experiments were conducted under different temperature-humidity combinations, and the radon release rate and effective decay constant were estimated by nonlinear regression. The results showed that the radon release rate increased with both temperature and relative humidity (RH). At a temperature of 25°C and a relative humidity of 98%, the value of radon release rate was 1.09 ± 0.04 mBq s-1, while at a temperature of 16°C and a relative humidity of 38%, the value of radon release rate was 0.30 ± 0.01 mBq s-1. Across the tested range, the radon release rate increased by approximately 263%, from the lowest-temperature/lowest-RH condition to the highest-temperature/highest-RH condition. The experimental methods verified in this paper, as well as the combined influence of temperature and humidity on radon release, provide a reference for the study of radon release rates of autunite and similar uranium minerals, and offer basic data and theoretical support for the application of autunite as an inexpensive and stable radon source.