Experimental study of dependence on humidity and flow rate for a modified flowthrough radon source

Abstract

Flow-through radon sources were widely utilized in the calibration of radon equipment and radon studies. In this paper a broken 266Ra source which was made in 1983 by the Pylon Inc. was modified to a new flow-through radon source. The humidity and flow rate dependence of the new flow-through radon source was studied to get a reliable large-scale radon source. The results show that the equilibrium radon concentration of the new flow-through radon source is rather sensitive to flow rate, especially below 1 L/min of flow rate, which sharply decreases with the flow rate rising, however, it increases with the relative humidity rising. The radon emanation coefficient does not depend on the flow rate of 0.6–2.57 L/min. However, the radon emanation coefficient increases up exponentially with the rising of the air humidity, it increases up slowly at the relative humidity of 4–50%, but it does fast at the relative humidity of 60–85%. The humidity dependence of flow-through radon sources is more obvious than diffusion radon sources because a dominative radon transport mode from the solid source material into the air is seepage rather than diffusion.