[en] There are studies to measure and model the radon concentration in soil gas and some studies have been carried out in the field to confirm regional and seasonal characteristics. in this study of radon exhalation rate from soil around Daegu, measuring radon concentration in a detector volume as a function of time and getting the initial increase rate from fitting were conducted outdoor by using RAD7 detector and its surface emission chamber. In this study, for two locations near Daegu, radon was measured outdoor and radon exhalation rates were calculated from the increase rates. In KNU, radon exhalation rate from soil was 15.14±0.87 Bq/m²s, in GC, 5.13±1.25 Bq/m²s. And radon's parent nuclides' concentration in KNU was also higher than GC's. But as for thoron, correlation between thoron exhalation rate and parent nuclide concentration can't be seen clearly. Afterward the measurement will be made in more sites and exhalation rate will be analyzed in association with parent nuclides activity in soil and spatial gamma dose rates or gamma exposure rates from monitoring ion chambers.

[en] Many studies have been done to analyze the detector dead time, including GM counter, based on the changed of the statistical parameters. One of the methods proposed from these studies is variance-to-mean ratio (VTMR) method. By this method, the dead time can be inferred using the degree of the distortion of Poisson statistic of measured count compared to the true count. Analytical formulas of variance to mean ratio of some dead time models have been derived in previous studies. Two models that were studied in this paper are nonparalyzable (NP) and paralyzable (P) models. In the nonparalyzable model, the events that occur during dead time portion of the detector are not counted and the dead time is not extended, while in the paralyzable model, events that occur in dead time portion are not counted and also cause the dead time reset and extended. Other model is hybrid model that can be in NP-P model or P-NP model. Coefficient of variation of the distorted time interval distribution resulted in GMSIM has been implemented to determine the dead time of the nonparalyzable and paralyzable model. The resulted nonparalyzable and paralyzable dead time by the variance to mean ratio and the coefficient of variation of time interval distribution are very close. Therefore both method can be used depend on the availability of the measurement system needed.