Influence of Fiber-Reinforced Concrete on Radon Concentrations

The influence of construction materials on the atmospheric radon concentration in an underground facility at the Nevada Test Site was examined. Radon (${}^{222}\mathrm{Rn}$ only) concentrations within the supporting fiber-reinforced concrete (fibercrete) and the native soil were quantified and compared. The average activity concentrations of ${}^{222}\mathrm{Rn}$ were $39\pm 1$ and $12\pm 1\mathrm{Bq}{\mathrm{kg}}^{-1}$ for the native soil and fibercrete, respectively. The average emanation coefficients of ${}^{222}\mathrm{Rn}$, measured via Lucas cell scintillation, were significantly higher for the cured fibercrete at $0.078\pm 0.029$, than for the dried native soil at $0.0053\pm 0.0006$. The emanation coefficient for the in situ native soil is estimated to be $0.020\pm 0.004$. In situ exhalation rates were also determined using passive-diffusion charcoal canisters. The average exhalation rate for the native material surface was $5.8\pm 0.6\mathrm{mBq}{m}^{-2}{s}^{-1}$. This was significantly higher $(p=9\times {10}^{-5})$ than for the fibercrete surface, which exhibited an average exhalation rate of $2.7\pm 0.7\mathrm{mBq}{m}^{-2}{s}^{-1}$. Based on these results, it can be concluded that the addition of fibercrete to wall surfaces reduces the radon concentration in this underground environment.