Measurement of equilibrium factors in various environments

Hashimoto, Hiroki*; Tamakuma, Yuki*; Yamada, Ryohei  ; Hosoda, Masahiro*; Tokonami, Shinji*

Radon is well known as a secondary risk factor for lung cancer next to tobacco. Thus, it is important to evaluate an inhalation dose from radon and its progeny from the viewpoint of radiation protection. In terms of the dose assessment, an equilibrium factor is commonly used to convert from the radon concentration to the equilibrium equivalent radon concentration (EERC), which indicates collective concentration of radon progeny, because it is easier to measure radon comparing to radon progeny. However, the equilibrium factor is known to vary in time and space so that it should be measured at various places in different seasons. In this study, the equilibrium factor was evaluated in various environments such as Japanese dwellings, a tourist cave and outdoors around an active volcano.