Byung-Uck Chang

Comparative analysis of radon, thoron and thoron progeny concentration measurements

This study examined correlations between radon, thoron and thoron progeny concentrations based on surveys conducted in several different countries. For this purpose, passive detectors developed or modified by the National Institute of Radiological Sciences (NIRS) were used. Radon and thoron concentrations were measured using passive discriminative radon-thoron detectors. Thoron progeny measurements were conducted using the NIRS-modified detector, originally developed by Zhuo and Iida. Weak correlations were found between radon and thoron as well as between thoron and thoron progeny. The statistical evaluation showed that attention should be paid to the thoron equilibrium factor for calculation of thoron progeny concentrations based on thoron measurements. In addition, this evaluation indicated that radon, thoron and thoron progeny were independent parameters, so it would be difficult to estimate the concentration of one from those of the others.

Nationwide survey of radon levels in Korea

Abstract— A nationwide radon survey was conducted to provide data on the annual average indoor radon concentration in Korean homes. This survey also provided data on the variation of radon concentration with season, house type, and building age. The arithmetic mean (AM) of annual radon concentration in Korean homes was 53.4 ± 57.5 Bq m−3. The indoor radon concentration showed a lognormal distribution with a geometric mean (GM) and its standard deviation (GSD) of 43.3 ± 1.8 Bq m−3. The radon concentrations in the traditional Korean- style houses were about two times higher than those in apartments and row houses. The average annual outdoor radon concentration was 23.3 Bq m−3. The average annual effective dose to the general public from radon was 1.63 mSv y−1.

NATIONAL RADON SURVEY IN KOREA

To estimate annual average concentrations in Korean dwellings and the effective dose to the general public, nationwide surveys on radon were conducted in 1989, 1999-2000 and 2002-2005. The total number of dwellings was about 5600. A survey of thoron and its decay products was also conducted in 2002-2005. In 2008-2009, a new radon survey in 1100 public buildings was conducted. The annual arithmetic (AM) and geometric (GM) means of indoor radon concentration in total were 62.1 ± 66.4 and 49.0 ± 1.9 Bq m(-3), respectively. The annual AM and GM means of indoor thoron concentrations were 40.4 ± 56.0 and 10.7 ± 2.9 Bq m(-3), respectively. The radon and thoron concentrations in detached houses were much higher than those in apartments. The locations of the high radon or thoron houses seem to be correlated with the concentrations of their parent nuclides in surface soil. The mean individual doses of radon and thoron were calculated to be 1.65 and 0.17 mSv y(-1), respectively.

Indoor radon distribution of subway stations in a Korean major city

The overall survey on indoor radon concentration was conducted at all subway stations in a major city, Daejeon in the central part of Korea. It was quarterly performed from September 2007 to August 2008. The annual arithmetic mean of indoor radon concentration of all the stations was 34.1+/-14.7 Bq m(-3), and the range of values was from 9.4 to 98.2 Bq m(-3). The radon concentrations in groundwater (average 31.0+/-0.8 Bq m(-3)) were not significantly high in most stations, but the concentration (177.9+/-2.3 Bq L(-1)) of one station was over the level of 148 Bq L(-1) in drinking water proposed by U.S. EPA. Based on indoor survey results, the approximate average of the annual effective dose by radon inhalation to the employees and passengers were 0.24 mSv y(-1), and 0.02 mSv y(-1), respectively. Although the effective dose based on the UNSCEAR report was potentially estimated, for more accurate assessment, the additional survey on the influence by indoor radon will be necessary.

Determination of low 137Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method

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.

Medically used radionuclides (131I, 99mTc) in the urban sewage system: the case of the Daejeon metropolitan city, Korea

In order to assess the behaviour of radioactivity (specifically (131)I concentrations in wastewater and sludge at sewage treatment plant) discharged into municipal sewage by therapy patients receiving treatment, the use of radiopharmaceuticals in four hospitals was quantitatively evaluated and the patients were classified by their residence. (131)I concentrations were estimated using a simple assumption model for radioiodine treatments of 94 patients, and measured by HPGe in inflow points, respectively. A good agreement was found between (131)I concentrations estimated with the model and those measured in the inflow points at the sewage treatment plant.

Radon exposure assessment for underground workers: a case of Seoul Subway Police officers in Korea

The objective of this study is the systematic and individual assessment of the annual effective dose due to inhaled radon for the Seoul Subway Police officers, Korea. The annual average radon concentrations were found to be in the range of 18.9-114 Bq·m(-3) in their workplaces. The total annual effective doses which may likely to be received on duty were assessed to be in the range of 0.41-1.64 mSv·y(-1). These were well below the recommended action level 10 mSv·y(-1) by ICRP. However, the effective doses were higher than subway station staff in Seoul, Korea.

The current status of NORM/TENORM industries and establishment of regulatory framework in Korea

During the last several years, a nationwide survey on naturally occurring radioactive material (NORM)/technologically enhanced naturally occurring radioactive materials (TENORM) industries has been conducted. Because of the rapid economic growth in Korea, the huge amount of raw materials, including NORM have been consumed in various industrial areas, and some representative TENORM industries exist in Korea. Recently, the Korean government decided to establish a regulatory framework for natural radiation, including NORM/TENORM and is making efforts to introduce relevant publically consent regulations on the basis of international safety standards.

Comparison of Natural Radioactivity of Commonly Used Fertilizer Materials in Egypt and Japan

Specific activities of 238U, 232Th, and 40K in the environment have been redistributed by the use of fertilizers in agriculture so their concentrations in fertilizer materials should be measured to identify the safe utilization of fertilizers. In the present work, the specific activities of these radionuclides in five commonly used fertilizers in Egypt and five fertilizers used in Japan were measured by HPGe and -ray spectrometry. The average values of 238U, 232Th, and 40K in Japanese fertilizers were less than their values in Egyptian fertilizers but both had some samples with specific activities greater than the recommended limiting values. The radiological hazards of radium equivalent activity (), external () and internal () indexes, alpha and gamma indexes, and annual effective dose, due to the presence of these radionuclides, were calculated and compared with each other.

Geographical distribution of indoor radon and related geological characteristics in Bonghwa County, a provisional radon-prone area in Korea.

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.