[en] Phosphogypsum is material produced as a byproduct in fertilizer industry and is generally used for building materials. This material may contain enhanced radium-226 (226Ra) activity concentration compared to its natural concentration that may lead to indoor radon accumulation. Therefore, an accurate measurement method is proposed in this study to determine 226Ra activity concentration in phosphogypsum sample, considering the potential radon leakage from the sample container. The International Atomic Energy Agency (IAEA) phosphogypsum reference material was used as a sample in this study. High-purity germanium (HPGe) gamma spectrometry was used to measure the activity concentration of the 226Ra decay products, i.e., 214Bi and 214Pb. Marinelli beakers sealed with three different sealing methods were used as sample containers. Due to the potential leakage of radon from the Marinelli beaker (MB), correction to the activity concentration resulted in gamma spectrometry is needed. Therefore, the leaked fraction of radon escaped from the sample container was calculated and added to the gamma spectrometry measured values. Total activity concentration of 226Ra was determined by summing up the activity concentration from gamma spectrometry measurement and calculated concentration from radon leakage correction method. The results obtained from 214Bi peak were 723.4±4.0 Bq·kg−1 in MB1 and 719.2±3.5 Bq·kg−1 in MB2 that showed about 5% discrepancy compared to the certified activity. Besides, results obtained from 214Pb peak were 741.9±3.6 Bq·kg−1 in MB1 and 740.1±3.4 Bq·kg−1 in MB2 that showed about 2% difference compared to the certified activity measurement of 226Ra concentration activity. The results show that radon leakage correction was calculated with insignificant discrepancy to the certified values and provided improvement to the gamma spectrometry. Therefore, measuring 226Ra activity concentration in TENORM (technologically enhanced naturally occurring radioactive material) sample using radon leakage correction can be concluded as a convenient and accurate method that can be easily conducted with simple calculation

[en] The radon concentrations in soil air were measured before and after a rainfall. ²²⁶Ra concentration, porosity, moisture content and temperature in soil were measured at Kyungpook National University in Daegu. As the results of measurement and analysis, the arithmetic mean of measured ²²²Rn concentration increased from 12100 ± 500 Bq/m³ to 16200 ± 600 Bq/m³ after the rainfall. And the measured ²²⁶Ra concentration was 61.4 ± 5.7 Bq/kg and the measured porosity was 0.5 in soil. The estimated values of ²²6Ra concentration and porosity using diffusion model of ²²²Rn in soil were 60.3 Bq/kg and 0.509, respectively. The estimated values were similar to the measured values. ²²²Rn concentration in soil increased with depth and moisture content. The estimations were obtained through fitting based on the diffusion model of ²²²Rn using the measurement values. The measured depth profiles of ²²²Rn were similar to the calculated depth profiles of ²²²Rn in soil. We hope that the results of this study will be useful for environmental radiation analysis.

[en] The activity level associated with the detection limit is the Minimum Detectable Activity (MDA). The MDA plays an important role in low level environmental activity measurements because it defines the smallest activity of radionuclide which can be detected in a sample with a detecting system, e.g. an HPGe system. Preliminary results showed that MDAs tend to decrease for prolonged measurement time, as expected. As measurement time increases, some collection of counts which wasn’t identified as peaks gets to become an identified peak (¹37Cs peak at t = 4 hours and 228Ac peak at t = 39 hours) and shows a big MDA decrease. The MDA reduction was about 23% ⁓ 36% for Currie method and about 38% ⁓ 51% for KTA method. The reduction is thought to come from the difference algorithm in the background count calculation, R.O.I estimation and its assumptions. The future scopes of this study will include detailed MDA analysis to explain the MDA reduction, introduction of variance reduction factor or deviation from Poisson statistics for the analysis of background counts.

[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] Korea institute of nuclear safety has operated monitoring system(Ion chamber, Scintillation detector, Thermoluminescence Dosimeter). Gamma exposure rate dependent on regional environment, season and diurnal(daily) variation, meteorological factor etc. There are many variable so that analysis of gamma exposure rate is too complicated. This paper confirmed diurnal variation and analyzed relation radionuclides in the soil and gamma exposure rate. For 10 monitoring locations, we compared diurnal(daily) variation of gamma exposure rate measured by monitoring ion chambers with the concentrations of radionuclides of the soils nearby the ion chambers. Using the data provided by IERNet, the gamma exposure rates are analyzed into four types. The concentrations of radioisotopes of the soil nearby 10 monitoring locations are obtained using a HPGe detector system

[en] As the use of X-ray tubes is widely spread mainly for medical diagnostic purposes or industrial applications, there is increasing demand for accurate and convenient way getting of X-ray beam spectral information. While measurement methods may provide quite accurate spectral information, these methods still require expensive detectors (example: HPGe, High Purity Germanium detector) and some conversion of measurement information into real spectrum. It is concluded that Laplace transform-based spectral reconstruction technique given in equations (1) and (2) works well for a 50-kV X-ray source. In this paper we obtained the attenuation curve by the use of MCNPX simulations. We were able to rebuild the X-ray spectrum of 50 kV through this research by Monte Carlo simulation (fitting parameters, a: 1.2921, b: 0.2342, ν: 0.6190, R-squared: 0.9930)

[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.

[en] To compare the measurement results of a portable survey meter with a soil-based dose rate assessment method, the gamma absorbed dose rates in the air were measured at 27 sites. The soil-based gamma absorbed dose rates in the air were calculated using established conversion factors and the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K of the soil at the sites. The gamma absorbed dose rate averages of the portable survey meter, and computing from the activity concentrations in the soil were 65.8 ± 4.26 and 64.8 ± 3.68 nGy.h^-1, respectively. A significant positive correlation was found in the comparison between the evaluated gamma absorbed dose rates from soil radioactivity and in the air. Conversion factors based on the local soils converting to the absorbed dose rate were computed from the portable survey meter data and the soil activity concentrations, and it was compared with others. (authors)