Estimation of surface concentration of radon decay products from gamma dose rate change after rain

A method to estimate the surface concentration of radon decay products ²¹⁴Pb and ²¹⁴Bi from gamma dose rate changes due to rainfall has been developed. The conversion from the dose rate to surface concentration was performed by a dose rate model considering geometric conditions such as buildings and ground undulations around each monitoring station (MS). This method of calculating dose rate increase (DRI) was successful in reproducing the difference in the shape of the DRI decrease due to differences in the initial ²¹⁴Bi/²¹⁴Pb. The estimated concentration exhibited differences among the MSs despite uniform depositions. This difference was considered to have been caused by surface run-off and infiltration of radionuclides. (author)