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 (²²²Rn only) concentrations within the supporting fiber-reinforced concrete (fibercrete) and the native soil were quantified and compared. The average activity concentrations of ²²²Rn were 39(plus-minus)1 and 12(plus-minus)1 Bq kg-¹ for the native soil and fibercrete, respectively. The average emanation coefficients of ²²²Rn, measured via Lucas cell scintillation, were significantly higher for the cured fibercrete at 0.078(plus-minus)0.029, than for the dried native soil at 0.0053(plus-minus)0.0006. The emanation coefficient for the in situ native soil is estimated to be 0.020(plus-minus)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(plus-minus)0.6 mBq m^-1 s^-1. This was significantly higher (p= 9×10^-5) than for the fibercrete surface, which exhibited an average exhalation rate of 2.7 (plus-minus)0.7 mBq m^-1 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.