Time variation of ~(222)Rn concentration and gamma level in a half-basement room

摘要

Correlation between ~(222)Rn (radon) concentration and gamma level in a half-basement has been discussed. In order to decrease the background count of a whole-body counter (WBC), a ventilation blower of 72 m~2h~(-1) was installed. The device succeeded in a big reduction of radon concentration in the half-basement and then the background of WBC ( NaI(Tl) ) decreased to the 765% of the saturated value. Through a radon saturation test the exhalation rate of radon from concrete wall was estimated as 2.1 Bqm~(-2)h~(-1) by a simple model calculation. In addition, through a ventilation test, the procedure was analyzed by another simple model.