Transport of Radon in Still Water under Steady - State and Transient Conditions

The transport of Rn through sealed, horizontal 2.54 cm diameter tubes filled with still water was observed to be significantly greater than that predicted solely from molecular diffusion. The rate of Rn transport was also found to be related to the concentration of Rn in the water. A constant source of radon producing an air concentration ranging from 1.1 to 176 Bq cm was connected to one end of a horizontal, insulated tube filled with water ranging from 30 to 52 cm in length. Continuous measurements of radon in air under transient and steady-state conditions were obtained using ZnS(Ag) alpha scintillators that were connected at each end of the water filled diffusion channel. Conventional values for pure molecular diffusion of radon in water range from 1.14 x 10 to 1.56 x 10 cm sec. Values for radon transport observed in this study are from 30 to 50 times greater than the rates cited for molecular diffusivity. Microturbulence produced by alpha particles from the decay of radon and its progeny may be responsible for eddy diffusivity observed in our experiments ranging from 5.14 x 10 to 8.14 x 10 cm sec. Theoretical analysis demonstrates that the energy associated with alpha decay of radon and its short-lived decay products in the water is sufficient to induce micro-turbulence in the diffusion channels to explain the ten-fold enhancement of radon transport observed in this study. This phenomenon of “radio-turbulence” may have significance for predicting the fate of radioactive wastes in soil and ground water, the geological disposal of spent fuel, nuclear fuel integrity analysis, and for studying the fate of radio-labeled pharmaceuticals in the body where the biokinetics could be affected by the energy associated with radioactive decay.