Earticle

Potential economic impact of a hypothetical severe accident at a nuclear power plant(Uljin units 3/4) was estimated byapplying the Delphi method, which is based on the expert judgements and opinions, in the process of quantifying uncertain factors. Forthe purpose of this study, it is assumed that the radioactive plume directs the inland direction. Since the economic risk can be dividedinto direct costs and indirect effects and more uncertainties are involved in the latter, the direct costs were estimated first and theindirect effects were then estimated by applying a weighting factor to the direct cost. The Delphi method however subjects to risk ofdistortion or discrimination of variables because of the human behavior pattern. A mathematical approach based on the Bayesianinferences was employed for data processing to improve the Delphi results. For this task, a model for data processing was developed.One-dimensional Monte Carlo Analysis was applied to get a distribution of values of the weighting factor. The mean and medianvalues of the weighting factor for the indirect effects appeared to be 2.59 and 2.08, respectively. These values are higher than the valuesuggested by OECD/NEA, 1.25. Some factors such as small territory and public attitude sensitive to radiation could affect thejudgement of panel. Then the parameters of the model for estimating the direct costs were classified as U- and V-types, and two-dimensional Monte Carlo analysis was applied to quantify the overall economic risk. The resulting median of the overall economic riskwas about 3.9% of the gross domestic products(GDP) of Korea in 2006. When the cost of electricity loss, the highest direct cost, wasnot taken into account, the overall economic risk was reduced to 2.2% of GDP. This assessment can be used as a reference for justifyingthe radiological emergency planning and preparedness.

This paper describes a dynamic compartment model to predict the time-dependent 14C activity in a plant as a result of adirect exposure to an amount of 14CO2for a short period of time, and experimental results for the model validation. In the model, theplant consists of two compartments of the body and ears, and five carbon fluxes between the compartments, which are the function ofparameters relating to the growth and photosynthesis of a plant, are considered. Model predictions were made for an investigation intothe effects of the exposure time, the elapsed exposure time, and the model parameters on the 14C radioactivity of a plant. The presentmodel converged to a region where the specific activity model is applicable when the elapsed time of the exposure was extended up tothe harvest time of a plant. The 14C activity of a plant was predicted to be the greatest when the exposure had happened in the periodbetween the flowering and ears-maturity on account of the most vigorous photosynthesis rate for the period. Comparison of modelpredictions with the observed 14C radioactivity of rice plants showed that the present model could predict the 14C radioactivity of the riceplants reasonably well.

In this study, we examined the effect of hydroxyl radical generated by -ray and UV irradiation on shrinkage of vitreousbody. Change in gel ratio of vitreous body and change in the properties of its components (collagen, sodium hyaluronate)were analyzed. By comparing these results, the amount of hydroxyl radical, which induces the considerable shrinkage ofvitreous body, was evaluated from theoretical calculation based on experimental condition and some reported kineticparameters. It was concluded that the integrated amount of hydroxyl radical required to liquefy half of the vitreous body(Vitreous body gel ratio = 50%) was estimated as 140 µmolg-1from -ray irradiation experiment. Also, from UVirradiation experiment result, it was confirmed that the effect of hydroxyl radical is larger than that of other reactive species.The causes of shrinkage of vitreous body are supposed as follows, 1) decrease in viscosity by cleavage of glycoside bondin sodium hyaluronate, 2) leaching of collagen from vitreous body and 3) leaching of crosslinked products and scissionproducts of collagen.

In Korean nuclear power plants (NPPs), two thermoluminescent dosimeters (TLD) were provided to workers who work inan inhomogeneous radiation field; one on the chest and the other on the head. In this way, the effective dose for radiation workers atNPPs was determined by the high deep dose between two radiation dose from these TLDs. This represented a conservative method ofevaluating the degree of exposure to radiation. In this study, to prevent the overestimation of the effective dose, field applicationexperiments were implemented using two-dosimeter algorithms developed by several international institutes for the selection of anoptimal algorithm. The algorithms used by the Canadian Ontario Power Generation (OPG) and American ANSI HPS N13.41, NCRP(55/50), NCRP (70/30), EPRI (NRC), Lakshmanan, and Kim (Texas A&M University) were extensively analyzed as two-dosimeteralgorithms. In particular, three additional TLDs were provided to radiation workers who wore them on the head, chest, and back duringmaintenance periods, and the measured value were analyzed. The results found no significant differences among the calculatedeffective doses, apart from Lakshmanan's algorithm. Thus, this paper recommends the NCRP(55/50) algorithm as an optimal two-dosimeter algorithm in consideration of the solid technical background of NCRP and the convenience of radiation works. In addition, itwas determined that a two-dosimeter is provided to a single task which is expected to produce a dose rate of more than 1 mSv/hr, adifference of dose rates depending on specific parts of the body of more than 30%, and an exposure dose of more than 2 mSv.

In order to determine the effect of extremely low frequency electromagnetic fields (ELF-EMF) on the frequency ofmicronuclei (MN), aneuploidy and chromosomal rearrangement induced by bleomycin (BLM) in human fibroblast cells, a 60 Hz ELF-EMF of 0.8 mT field strength was applied either alone or with BLM throughout the culture period and a micronucleus-centromere assaywas performed. Our results indicate that the frequencies of MN, aneuploidy and chromosomal rearrangement induced by BLMincreased in a dose-dependent manner. The exposure of cells to 0.8 mT ELF-EMF followed by BLM exposure for 3 hours led tosignificant increases in the frequencies of MN and aneuploidy compared to BLM treatment for 3 hours alone (p<0.05), but no significantdifference was observed between field exposed and sham exposed control cells. The obtained results suggest that low density ELF-EMF could act as an enhancer of the initiation process of BLM rather than as an initiator of mutagenic effects in human fibroblast.

Recently a high-quality voxel model of a Korean adult male was constructed at Hanyang University by using very highresolution serially-sectioned anatomical images of a cadaver, which was provided by the Korean Institute of Science and TechnologyInformation (KISTI). Most existing voxel phantoms are developed based on an individual in the supine posture. This study convertedthe HDRK-Man voxel model into surface model and adjusted the flattened back of the HDRK-Man to a normal shape in the uprightposture using 3D graphic softwares such as 3D-DOCTORTM, Rapidform2006, Rhinoceros4.0, MAYA8.5. The effective doses ofadjusted model were compared with those of unadjusted model for some standard irradiation geometries (i.e., AP, PA, LLAT, RLAT).In general, the differences were not very large and, among those, the largest difference was found for the PA radiation geometry, asexpected. These methodologies can be used for the development of various deformed posture models of HDRK-Man in the later stageof this project.

To ensure the performance of radon detectors, three passive radon detectors (RadTrak®, Radopot®, and E-PERM®) have beenreviewed. The difference ratios of RadTrak and Radopot tested in the radon standard chamber were -13.2% and -6.0%, respectively,which were in good accordance within 20% of the value measured by AlphaGUARD®. To ensure the performance of the long termmeasurement, the 3 detectors were installed at the same position of approximately one hundred of dwellings for one year. Thecorrelation curve between RadTrak and Radopot shows good agreement with a correlation coefficient (R2) of 0.91. However, Thecorrelation curve between E-PERM and Radopot shows bad agreement (R2= 0.021). In addition, the distribution map of annual meanindoor gamma dose rate measured with E-PERM was not in accordance with the distribution map of outdoor gamma dose ratemeasured by Portable Ion Chamber. According to the results, some requisites for the selection of the radon passive detectors in thelarge-scale indoor radon survey were discussed.

The internal dose by food consumption mostly accounts for radiological dose of public around nuclear power plants (NPPs).But, food consumption rates applied to off-site dose calculation in Korea which are the result of field investigation around Kori NPP bythe KAERI (Korea Atomic Energy Research Institute) in 1988, are not able to reflect the latest dietary characteristics of Korean. Thefood consumption rates to be used for radiological dose assessment in Korea are based on the maximum individual of US NRC(Nuclear Regulatory Commssion) Regulatory Guide 1.109. However, the representative individual of the critical group is considered inthe recent ICRP (International Commission on Radiological Protection) recommendation and European nations' practice. Therefore, thestudy on the re-establishment of the food consumption rates for individual around nuclear power plant sites in Korea was carried out toreflect on the recent change of the Korean dietary characteristics and to apply the representative individual of critical group to domesticregulations. The Ministry of Health and Welfare Affairs has investigated the food and nutrition of nations every 3 years based on theLaw of National Health Improvement. The statistical data such as mean, standard deviation, various percentile values about foodconsumption rates to be used for the representative individual of the critical group were analyzed by using the raw data of the nationalfood consumption survey in 2001~2002. Also, the food consumption rates for maximum individual are re-estimated.