[en] The evaluation of the hazard posed to the skin by very small radioactive sources (diameter < 1mm) has become popularly known as the 'hot particle' problem in European and American nuclear reactor facilities. In this study, research to detect hot particle was performed in Wolsung Nuclear power plant (NPP) in Korea

[en] As well as differences in the season, there is a difference in the concentration of each year. In addition we consider that crops have different absorption rates of radioactive material depending on the time of the growth status. That will have an impact on how much crops contaminated by radioactive material. That's why we choice the rice plant. And we applied absorbed rate factor to calculate absorbed material density in the rice. The purpose of this study is to compare the results between the ground concentration of radioactive material and absorbed material density in the rice in each season. Lastly we calculate the annual effective dose on the assumption that people eat the contaminated rice in each season from 2008 to 2010. Calculated Effective dose around the 1,3,5 km less than Effective dose limits that 1mSv. It is not give a major impact to public. The different results could be expected, however, if the accident emitting more radioactivity was assumed. We expect that results obtained can be revised after the repeating simulation of MACCS2 with more weather data

[en] Computational anthropomorphic phantoms are computer models of human anatomy used in the calculation of radiation dose distribution in the human body upon exposure to a radiation source. Depending on the manner to represent human anatomy, they are categorized into two classes: stylized and tomographic phantoms. Stylized phantoms, which have mainly been developed at the Oak Ridge National Laboratory (ORNL), describe human anatomy by using simple mathematical equations of analytical geometry. Several improved stylized phantoms such as male and female adults, pediatric series, and enhanced organ models have been developed following the first hermaphrodite adult stylized phantom, Medical Internal Radiation Dose (MIRD)-5 phantom. Although stylized phantoms have significantly contributed to dosimetry calculation, they provide only approximations of the true anatomical features of the human body and the resulting organ dose distribution. An alternative class of computational phantom, the tomographic phantom, is based upon three-dimensional imaging techniques such as Magnetic Resonance (MR) imaging and Computed Tomography (CT). The tomographic phantoms represent the human anatomy with a large number of voxels that are assigned tissue type and organ identity. To date, a total of around 30 tomographic phantoms including male and female adults, pediatric phantoms, and even a pregnant female, have been developed and utilized for realistic radiation dosimetry calculation. They are based on MRI/CT images or sectional color photos from patients, volunteers or cadavers. Several investigators have compared tomographic phantoms with stylized phantoms, and demonstrated the superiority of tomographic phantoms in terms of realistic anatomy and dosimetry calculation. This paper summarizes the history and current status of both stylized and tomographic phantoms, including Korean computational phantoms. Advantages, limitations, and future prospects are also discussed

[en] Some issues concerning the new system of radiation protection of 2007 ICRP recommendations are raised and discussed. Parts of them are related to the concept of terms or approaches to control and the rest are to foster common understanding of the system. The issues include questions involving the definition of potential exposure and the existing exposure situations, position of accidental exposure in medicine in the protection system, concerns about the single source and constraints, and an approach for control of radon exposures. (author)

[en] The reactions of the public in Korea to the nuclear accident at the Fukushima Daiichi plants in Japan, particularly over-reactions, are reviewed, with the conclusion that significant radioactive contamination of a small country could lead to a severe national crisis. The most important factor is the socio-economic damage caused by stigma, which in turn is caused by a misunderstanding of the radiation risk. Given that nuclear power is an important choice in the face of the threat of climate change, the public's perceptions need to be changed at any cost, not only in those countries operating nuclear power plants but globally as well. (note)

[en] This study was performed for suggesting a simulation method that can create accurate virtual models of objects with free curved surfaces and perform distortion-free MCNPX simulations. The virtual models acquired by using 3D scan equipment with an accuracy of approximately ±0.025 mm in length, compare with actual objects and are comprised of 11104 polygons. Generally, MCNPX simulations of objects with free curved surfaces are performed through voxelization. In this study, polygon model be tetrahedralized by TetGen for the construction of MCNPX geometry to distortion-free. Then, dose estimation was successfully performed after converting the virtual model into an MCNPX input. With this in mind, a voxelized model was constructed for comparison purposes. The dose estimation functions of the two models were found to be similar, showing a similar amount of computing time by using the mesh tally option with 2e7 histories: for the tetrahedralized model, 729.67 minutes; for the voxelized model, 720.11 minutes. (authors)

[en] In this study, issue on the skin dose averaging area was reviewed with the results of calculated dose distribution from various beta emitters. In case of dot-like contamination such as a hot particle, according to calculated results, over 99% of the dose was deposited within 1 mm radius. This result showed that the use of 10 cm² as the dose averaging area, recommended by the National Council on Radiation Protection and Measurement (NCRP), compromises the concept of dosimetry by intentionally including unexposed tissue volume to reduce the dose. Beside the approach recommended by NCRP, two other options were suggested and discussed. One option addressing a graded enforcement of the skin dose limit, considering the low probability of hot particle exposure, was proposed to avoid compromising the dosimetry concept. Though this option can give flexibility in the regulation of skin exposure, this option compromises the unified meaning of the dose limits. The other option addressed increase of the skin equivalent dose limit specifically for prevention of deterministic effects while applying a smaller averaging area for controlling stochastic effects. The first two options involve decision of the national or regional regulatory authority and the third involves actions at the International Commission on Radiological Protection (ICRP) level. (author)

[en] SMART (System-integrated Modular Advanced Reactor) is a small and medium size integrated reactor with 330 MW_th power which has been developed in Korea. In the SMART, some of the components such as steam generator, flow mixing header assembly and flow skirt are installed inside the reactor vessel and near the core, which lead to their activation. The components will be withdrawn for maintenance, inspection, replacement or decommissioning, which causes radiation fields from them. In order to evaluate their activities and radiation fields, a computer-based simulation was performed using the MCNPX code. We calculated the dose rates by distance from the surface of the components to 5 m away and the variation of dose rates over time. Dose rates near the withdrawn components are extremely high and the dose rate is still extremely high after sufficient cooling time. Thus, approach to these components must be prohibited and all of works relevant with the withdrawn components must be performed by remote control system. (author)

[en] The HRTM, however, was revised based on the recent experimental data in OIR (Occupational Intakes of Radionuclides) draft report of ICRP. The changes of respiratory tract model are predicted to directly affect bioassay data like retention and excretion functions. Lung retention function is especially important to internal exposure assessment for workers related to fuel manufacturing because the place could be contaminated by uranium. In addition, faecel samples are recommended to be used for in-vitro bioassay of uranium because of very slow excretion via urine. More reliable assessments for the workers in fuel manufacturing could be achieved by recalculation of bioassay data for uranium and the comparing study using original and revised HRTM. In this study, therefore, the lung retention and faecal excretion functions for inhalation of UO₂ and U₃O₈ were recalculated using revised HRTM and the results were compared with those of original HRTM. In this study the lung retention and faecal excretion functions for inhalation of UO₂ and U₃O₈ were calculated based on original and revised HRTM. The results show that the revised HRTM increases lung retention and uptakes to alimentary tract which cause the more faecal excretion. The results in this study confirm the effect of the changes of respiratory tract model on the uranium bioassay data although the more study is needed to apply to practical fields

[en] The ICRP (International Commission on Radiological Protection) provides the coefficients as point values without uncertainties, it is important to understand sources of uncertainty in the derivation of the coefficients. When internal dose coefficients are calculated, numerous factors are involved such as transfer rate in biokinetic models, absorption rates and deposition in respiratory tract model, fractional absorption in alimentary tract model, absorbed fractions (AF), nuclide information and organ mass. These factors have uncertainty respectively, which increases the uncertainty of internal dose coefficients by uncertainty propagation. Since the procedure of internal dose coefficients calculation is somewhat complicated, it is difficult to propagate the each uncertainty analytically. The development of module and calculation were performed by MATLAB. In this study, we developed the calculation module for uncertainty of the internal dose coefficient. In this module, uncertainty of various factor used to calculate the internal dose coefficient can be considered using the Monte Carlo sampling method. After developing the module, we calculated the internal dose coefficient for inhalation of ⁹⁰Sr with the uncertainty and obtained the distribution and percentile values. It is expected that this study will contribute greatly to the uncertainty research on internal dosimetry. In the future, we will update the module to consider more uncertainties