Measurement of radon exhalation parameters in normal concrete and its application in prediction model of indoor radon...

This study measured the radon exhalation parameters of normal concrete and developed a predictive model for indoor radon concentrations based on these parameters. Twenty-two concrete samples were collected from five provinces in China. The ²²⁶Ra content of the samples was determined using a GC3018 low-background HPGe γ-spectrometer, while porosity was measured with a BSD-TD-K fully automated true density and open porosity analyzer. Radon exhalation rates and the radon emanation fraction were quantified using the activated carbon sealed chamber method combined with γ-spectrometry. Radon diffusion length and diffusion coefficient were measured using an integrated system comprising a source chamber, diffusion window, accumulation chamber, and RAD7 radon detector. The normal concrete samples exhibited an average density of 2436 ± 93 kg/m³ and a mean radium content of 25 ± 10 Bq/kg. The average surface radon exhalation rate was 0.22 ± 0.12 mBq·m^-2·s^-1, and statistical analysis revealed a significant positive correlation between radium content and radon exhalation rate. The concrete samples demonstrated an average porosity of 13.4% ± 4.0%, a mean emanation fraction of 9.3% ± 3.3%, a mean radon diffusion length of 0.08 ± 0.04 m, and a mean radon diffusion coefficient of (0.016 ± 0.016) × 10^-6 m² s^-1. Model validation showed a mean relative percent deviation of 16% between predicted and measured indoor radon concentrations, indicating good agreement between the model predictions and experimental observations.