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In this study, in-situ and laboratory γ-ray spectroscopy techniques were compared to evaluate the activity concentration of natural radionuclides in soil. The activity concentrations of 238U (226Ra), 232Th, and 40K in the soil in 11 sites were simultaneously measured with in-situ portable HPGe and the NaI(Tl) detectors. In parallel, 55 soil samples collected from these sites were analyzed with a laboratory γ-ray spectroscopy technique (HPGe). A strong correlation was observed between the in-situ and laboratory HPGe techniques with a linear correlation coefficient (R2) of 0.99 for 226Ra and 232Th and 0.975 for 40K, respectively. The in-situ HPGe technique shows a strong correlation with the NaI(Tl) detector. γ-Rays cps of 226Ra, 232Th, and 40K of the NaI (Tl) detector were then converted to specific activities (Bq kg-1 unit) in soil using the empirical formulas obtained in this study. The absorbed dose rate in air at 1 m height above ground due to these radionuclides was calculated using the Beck's formula and the results were compared with measured values obtained with an high pressure ionization chamber. The results of the calculated and measured dose rate show a strong correlation of R2 = 0.96. The reliability and precision of analytical spectroscopy techniques of radioactivity and radiation dose were confirmed in this work.

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Radon exposure in schools is different from that in dwellings because the residence pattern is very different each other. So, when effective dose is calculated in schools, different approach should be considered from in dwellings. The aim of this study was to estimate actual effective dose due to inhaled radon considering the residence time in schools. It could help avoid overestimation when effective dose is calculated in schools. The range of radon concentration in 376 schools was 18.1-2810 Bq m-3 and that of annual effective dose was estimated 0.0902-8.92 mSv y-1 considering the residence time in spring and autumn semesters.

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The detailed indoor radon survey was conducted during a year (from September 2012 to August 2013) quarterly in Bonghwa county, one of the provisional radon-prone areas in Korea. The surveyed area was selected on the basis of previously conducted nationwide radon survey results. In order to minimise statistical and environmental uncertainties, ∼3 % of the entire dwellings were carefully selected based on the statistical annual report of Bonghwa county. The measurement is carried out by using solid-state nuclear track detector. The range of indoor radon concentration in each dwelling was 4.36-858 Bq m(-3) and that of annual effective dose due to inhaled radon of the resident in each dwelling was 0.19-23.5 mSv y(-1). Each dwelling was determined for geology criterion using one-way Analysis of Variance for the purpose of comparing indoor radon distribution with geology. Geographical distribution of indoor radon is closely related to the geological characteristics of basement rocks. In addition, the comparison between geographical distribution of indoor radon and terrestrial gamma radiation was done.

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A new method has been developed for analyzing (137)Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb (137)Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove (87)Rb, interference nuclide for beta counting. The AMP adsorbing (137)Cs was dissolved by sodium hydroxide solution, and then (137)Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from (137)Cs were measured with a low background gas-proportional alpha/beta counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used gamma-spectrometry method, this new AMP method was reliable and suitable for analyzing (137)Cs in deep seawater.

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A Nationwide survey on the natural radioactivity in industrial raw mineral commodities (17 kinds of domestic and 18 kinds of imported) that are representative minerals used in production and consumption in South Korea was conducted. The target industrial minerals can be categorized into two groups. The first group covers non-metallic and metallic raw minerals with low levels of radioactivity such as clay, silica sand, carbonates, bituminous and anthracite coal, iron ores, ilmenite, rutile, and phosphate ore. The other group comprises minerals with high levels of radioactivity including zircon and monazite. One hundred and sixty-four domestic and imported samples were analysed by gamma-ray spectroscopy using an HPGe detector. The (40)K content ranges from <0.00131 to 2.69Bq g(-1), and (226)Ra and (232)Th range over <0.0006 to 0.630 and <0.0008 to 0.474Bq g(-1), respectively. There was no anthropogenic radioactive signal in any of the samples.

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239+240Pu concentrations and 240Pu/239Pu atom ratios in coastal seas adjacent to the Korean Peninsula were determined, during the period 1999 to 2002, to assess the current distribution and to identify sources of Pu isotopes. 239+240Pu concentrations in surface waters ranged from 3.1 to 22.3 mBq m(-3) with higher concentrations in winter than in summer. 239+240Pu concentrations in seawaters around the Korean Peninsula are greater than that in the western North Pacific. 240Pu/239Pu atom ratios ranged from 0.18 to 0.33 with an average value of 0.25+/-0.03, which is significantly higher than the global fallout average. The 240Pu/239Pu atom ratios of the 2000 m deep entire water column in the south western part of the East Sea (Sea of Japan) was comparable to that observed in waters near Bikini Atoll. The higher 240Pu/239Pu atom ratios than that of global fallout may be explained by the hypothesis that the earlier input signal of low 240Pu/239Pu atom ratio (0.18-0.19) of global fallout plutonium in seas adjacent to the Korean Peninsula is being gradually diluted by the high 240Pu/239Pu atom ratio plutonium transported from the tropical Pacific Proving Grounds via prevailing ocean current.