[show abstract][hide abstract] ABSTRACT: The aim of this study was to survey the radon concentrations at 21 elementary schools in Gyeongju, Republic of Korea, to identify those schools with high radon concentrations. Considering their geological characteristics and the preliminary survey results, three schools were finally placed under close scrutiny. For these three schools, continuous measurements over 48h were taken at the principal's and administration office. The radon concentrations at one school, Naenam, exceeded the action level (148Bq/m(3)) established by the U.S. EPA, while those at the other two schools were below that level.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 04/2013; · 1.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: A fiber-optic radiation sensor (FORS), which is composed of an inorganic scintillator, a plastic optical fiber (POF), a photomultiplier tube (PMT), and a multichannel analyzer (MCA), was developed for gamma-ray energy spectroscopy. In this study, we selected a cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) as the sensitive element of the FORS and found that LYSO:Ce with dimensions of 3 × 3 × 15mm3 gives the best performance in obtaining a gammaray energy spectrum. The FORS allows us to measure the energy spectra of Co-60, Na-22, and Cs-137.
[show abstract][hide abstract] ABSTRACT: Sometimes, detection of thermal neutrons in the presence of gamma rays is required. This study developed and characterized an integrated fiber-optic radiation sensor for the simultaneous detection of thermal neutrons and gamma rays in a mixed radiation field. The performance of the integrated sensor was verified by measuring the distributions of thermal neutrons and gamma rays released from a nuclear fuel rod at the Kyoto University Critical Assembly. The experimental results show that the integrated sensor produced similar distribution patterns to those of thermal neutrons and gamma rays released from a fuel rod.
Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 04/2011; 69(4):711-5. · 1.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: Measuring the level of radioactive contamination in a high-radiation area with a complex geometry requires a new measuring system that can be operated remotely and free of electronic noise by radiation. In this study, a measuring system suitable for measuring high-level radioactive contamination in the narrow gap of a nuclear facility was developed. The measuring system was a fiber-optic remote system using an organic scintillator, epoxy resin and an optical fiber. The measuring system was tested for Cs-137 and Sr/Y-90 radiation sources, and could measure radioactive contamination remotely in a narrow area.
[show abstract][hide abstract] ABSTRACT: In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for brachytherapy dosimetry. Organic scintillators are made from a polystyrene base with wavelength-shifting fluors, and they do not disturb the radiation field due to their tissue or water-equivalent characteristics in a wide range of energies. The fiber-optic radiation sensor developed for this study provides a fast real-time response and convenient usage for brachytherapy dosimetry. For more accurate measurement, we have measured Cerenkov light using a dummy fiber and avoided dose measurement errors arising from high dose gradients in brachytherapy dosimetry. The Cerenkov light has been eliminated using a modified subtraction method. Also, the relative depth dose without the dose generated from Cerenkov lights is measured and compared with the results obtained using conventional EBT dosimetry films.
IEEE Transactions on Nuclear Science 07/2010; · 1.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: An optimization method based on genetic algorithm (GA), which is referred as MACroscopic Near-Optimal Shielding design (MACNOS), is proposed for the search for an optimal radiation shield configuration subject to a given set of constraints. In MACNOS, a GA is used to search for the optimal shielding design and the penalty strategy is employed to deal with the constraints. In order to confirm its capability to search for the optimal shielding design, MACNOS is applied for solving a simple problem with regard to radiation shielding optimization of a hypothetical spaceship reactor. The application shows that, keeping the constraints satisfied, MACNOS is able to seek for the shielding design that minimizes the total weight by changing the thickness and the material of the shield. Therefore, it is expected that MACNOS is potentially useful in the search for the optimal design configuration in the conceptual design phase, where the selection of the shielding material and the estimate of the thickness are necessary.
Annals of Nuclear Energy - ANN NUCL ENERG. 01/2010; 37(2):120-129.
[show abstract][hide abstract] ABSTRACT: This research evaluates the effect of physiological responses during electrical acupuncture (EA) stimulation on specific acupuncture points (APs: PC5 and PC6). A variety of special responses in the human body were determined by electroencephalogram (EEG), heart rate (HR) in an electrocardiogram (ECG), and skin impedance test for 2 groups, sham group as a control and a group under acupuncture stimulation. The total stimulation time in this study was set for 5 min since the effect of EA on all recorded parameters became stable within this period. According to the experiments, during EA stimulation of PC5 and PC6, the power spectrum of EEG showed that the number of low frequency waves was increased in all lobes. Heart rate variability measures of 10 subjects stimulation trials at PC6 and PC5 were compared to 10 subjects who received no stimulation treatment. In both the AP and the sham groups, the mean R-R interval increased significantly during EA stimulation. A comparison between the AP and non-AP group in terms of skin resistance measurement experiments revealed no difference in skin resistance. The results of this study verified that EA stimulation of APs (PC5, PC6) causes EEG changes, and ECG heart rate changes. However, from human skin impedance measurements, the beneficial effects were not sustained. These results may be helpful in the understanding of the mechanism underlying the effect of electrical acupuncture on PC6 and PC5.
The American Journal of Chinese Medicine 02/2009; 37(3):505-17. · 2.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study, we have fabricated non-contact temperature sensor using an infrared optical fiber for measuring temperature
distributions during radiofrequency ablation. We have measured an infrared radiation, which is transferred by a silver halide
optical fiber from the multi-points on the water around inserted electrode, using a thermopile sensor and the output voltages
of a thermopile sensor are compared with those of the thermocouple recorder. Also, the relationship between the temperatures
and the output voltages of a thermopile sensor at the measuring points is determined to obtain the temperature distribution.
The measurable temperature range of a fiber-optic non-contact temperature sensor is from 37 to 80 °C.
Keywordsfiber-optic sensor-infrared radiation-noncontact temperature sensor-radiofrequency ablation-silver halide optical fiber
[show abstract][hide abstract] ABSTRACT: A scintillating fiber-optic dosimeter has many advantages such as real-time readout, high-resolution measurement, water-equivalence
and no corrections for temperature, pressure and humidity. Organic scintillator which has water or tissue equivalent characteristics
is very important to measure absorbed dose, dose rate and dose distributions exactly without any corrections and due to its
small size, the sensitive volume enables accurate dose measurements in regions of high dose gradients with high spatial resolution.
In this study, a scintillating fiber-optic dosimeter with an organic scintillator is fabricated to measure high-energy photon
beam from a clinical linear accelerator. And we have measured linear responses of a fiber-optic dosimeter according to dose
rates and monitor units of a clinical linear accelerator. Also, a percent depth dose curve for 6MV photon beam with different
field sizes are obtained.
Keywordsorganic scintillator-fiber-optic dosimeter-photon beam-radiotherapy
[show abstract][hide abstract] ABSTRACT: In this study, a one-dimensional fiber-optic scintillating detector was developed for electron-beam therapy dosimetry. Each fiber-optic detector contains an organic scintillator as a sensitive volume and it is embedded and arrayed in a plastic phantom to measure one-dimensional high-energy electron-beam profiles of clinical linear accelerators. Plastic optical fibers guide the scintillating light which each detector probe generates to a photodiode array. The one-dimensional electron-beam profiles in the plastic phantom were measured in two different field sizes and for two electron-beam energies. Also, isodose and two-dimensional dose distributions in the plastic phantom were obtained using the one-dimensional scintillating detector array with two different electron beam energies.
IEEE Transactions on Nuclear Science 11/2008; · 1.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study, we fabricated a fiber-optic radiation sensor with an organic scintillator to measure the high-energy photon beam from a clinical linear accelerator, and a two-dimensional fiber-optic sensor array to measure high-resolution and real-time dose distributions for small field radiotherapy dosimetry. The scintillating lights generated from each organic sensor probe embedded and arrayed in a water phantom are guided by 10 m plastic optical fibers to the light-measuring device. Two-dimensional photon beam distributions in a water phantom were measured for photon beams with different energies and field sizes. Also, percent depth dose curves for 6 and 15 MV photon beams were obtained.
IEEE Transactions on Nuclear Science 11/2008; · 1.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: Usually, two kinds of light signals such as scintillating and Cerenkov light are generated in a fiber-optic dosimeter when a high energy electron beam is irradiated. The objectives of this study are to measure, characterize and remove a Cerenkov light generated in a scintillating fiber-optic dosimeter. The intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam from a linear accelerator, as a function of electron beam energy, and as a function of electron beam size using a photodiode amp system and a charge-coupled device. Also, a subtraction method using a background optical fiber without a scintillator is investigated to remove a Cerenkov light.
[show abstract][hide abstract] ABSTRACT: In this study, we have developed a non-contact temperature sensor using a silver halide optical fiber for medical endoscopic usage. We have measured an infrared radiation which is transferred by a silver halide optical fiber from a heat source using a thermal optical power-meter and a thermopile sensor. To increase the amount of infrared radiation through the silver halide optical fiber and to the infrared sensors, optical devices such as an infrared collimator and a focusing lens are used. The relationships between the temperatures of a heat source and the measured output signals are determined. The measurable temperature range of a fiber-optic temperature sensor is from 30 to 60degC. It is expected that a non-contact temperature sensor using an infrared optical fiber can be developed for medical and industrial usages based on the results of this study.
[show abstract][hide abstract] ABSTRACT: Activation products are generated from photoneutron capture reactions inside a linear accelerator (LINAC) used in a high energy X-ray cargo inspection facility. The activation products are estimated using MCNPX, Monte Carlo simulation code, in order to evaluate radiological safety in the facility. The result shows that the maximum radiation dose rate from the saturated activity in LINAC room is about 2.18E−06 Sv/h and 74-W-187 is the most significant radionuclide generated. It is, therefore, recommended that a proper measure to reduce the radionuclide is considered to protect occupational workers against the decay radiations.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2007; 265(2):615-620. · 1.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although the government admit the benefit of construction of a nuclear facility for national electric source, related policy could be developed and carried out only if the public, especially who have some stake on it, recognize the benefit and accept the policy. For public participation, Korea has a system of public-hearing in accordance with the law. Because of the absence of the detailed way for public opinion aggregation and for the reflection of the aggregated opinion, Korean public-hearing system is only a conceptual model. Therefore, some specific system for Korean Public-Hearing should be developed and applied. In this study, to share the right of decision making, which is an ultimate concept for public participation, decision making components and the characteristics of each phase are analyzed. The criteria weight for assessment and comparison with alternatives are founded as a valuation factor of the decision making components, which should be based on the social consensus. On these foundations, a system for aggregation and reflection of the public opinion was proposed. The system named 'CPDM' (Consensus based Participatory Decision Making) has three authority groups for decision making. At first, 'advisory experts group' play a role for the technical assessment and the serve utility value on the criteria for each alternatives. Next, 'participatory deliberation group' play a role for consensus building on the relative-importance (weight) between the criteria by feedback to promote degree of consensus. Lastly including gentlemen of the long robe, 'expert group for decision making' play a role to reflect the utility and weight and make a decision with agreement for performance of it. Also, in this study, a mathematical model for the quantification of the degree of consensus was conceptualized using Ordered Weighted Averaging (OWA) aggregation operator and fuzzy similarity theory, which is a comparison concept. Since this model enables influence of each criteria and each participant on collective consensus to be analyzed, a direction to promote consensus building can be derived. That is to say, this model can support consensus building and promote public acceptance for the nuclear industry and related policy. (authors)
[show abstract][hide abstract] ABSTRACT: Public participation is essential in each step of the nuclear-related decision-making process. Recently, the electronic systems using the Internet have become quite popular, and have emerged as a good medium for communicating with the public. In this study, a comprehensive utilization of electronic public participation was used to analyze public opinion on a given nuclear-related decision-making process. The degree of deliberation and meditation of the public participating in an electronic poll survey was evaluated, and the decision-making factors representing the personal characteristics of the poll respondents such as age, income, education, residence, degree of knowledge and concern were carefully incorporated when preparing the poll-survey questionnaire for its evaluation. Fuzzy analysis was used to assess and aggregate the responses to each decision-making factor. As a case study, this procedure was used to analyzing public opinion on the location of a low-level radioactive waste disposal facility on the campus of Seoul National University. The results show that there is a tendency of respondents who are on the negative side of the argument to be more deliberate and meditative in their decision-making process than those on the positive side. Knowledge and residence were found to be important decision-making factors.
Annals of Nuclear Energy 01/2006; 33(2):163-169. · 0.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Phosphogypsum board is a popular construction material used for housing panels in Korea. Phosphogypsum often contains (226)Ra which decays into (222)Rn through an alpha transformation. (222)Rn emanated from the (226)Ra-bearing phosphogypsum board has drawn the public concern due to its potential radiological impacts to indoor occupants. The emanation rate of (222)Rn from the board is estimated in this paper. A mathematical model of the emanation rate of (222)Rn from the board is presented and validated through a series of experiments. The back diffusion effect due to accumulation of (222)Rn-laden air was incorporated in the model and found to have a strong impact on the (222)Rn emanation characteristics.
Journal of Environmental Radioactivity 02/2005; 80(2):153-60. · 2.12 Impact Factor