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[en] Optical fibers have been used as sensing materials in various nuclear applications. Optical fiber sensors have proven to present several advantages as compared with other conventional sensors. They can be prepared in very small sizes and they are light enough to be easily put into very narrow channels such as between nuclear to be easily put into very narrow channels such as between nuclear fuel rods. No electrical power is needed to the sensor part so they are less susceptible to troubles in harsh environments such as underground and underwater. Optical fiber sensors cost relatively cheap to make, so that they are more suitable for multi-point radiation monitoring such as in nuclear power plants, accelerators, fusion study facilities. If one develops radiation sensors using scintillating optical fibers, that can directly measure the concentration of 3H or 14C in radioactive liquid, they can be useful tools to substitute the current liquid scintillation counters. They can be also used to measure the radioactivity of liquid radioactive wastes by dipping into the liquid wastes. Recently, several new scintillating materials of high density and low hygroscopicity have been found, and they can be transformed into good radiation-detection tools when they are combined with optical fibers. In this study, we have used commercially available plastic scintillating fibers of Bicron model BCF-12 (0.5mm, 1mm in diameter) to detect beta rays emitted from 3H, 14C. Several types of radiation sensors were constructed : each was constructed with thirty strands of the fibers being packed an aluminum tube. The optical signals generated inside the fiber bundle were converted into electrical pluses by a photomultiplier tube(PMT). The pulses were counted either through a non-coincidence circuit or a coincidence circuit. Two types of sensors were constructed for the non-coincidence counting. The open type (sensor A) is a sensor for which one end of the fibers is open and the other end is coupled with a light-transmitting fiber. The closed type (sensor B) is the one for which the fibers are bent so that both ends are coupled with a light -transmitting fiber leading to a PMT. For the fiber of 1mm diameter, only open type sensor was constructed due to the difficulty of bending. 3H or 14C solution was poured into the sensor and a direct contact was made between the solution and the fibers. For the coincidence circuit counting, each end of the sensor was connected with a transmission fiber which is connected to a PMT. The electrical pulse signals are fed into the coincidence circuit from which the output signals are supplied to an MCA system. the radioactive concentration of the solution is commonly 0.05, 0.1 and 0.2 mCi/ml for the 3H and 14C solutions. For the 14C solution, the sensors were also tested for the radioactive concentration of 1, 3 and 5μCi/ml. For the sensors considered, we measured the pulse height spectra using an MCA, and investigated the proportionality between the total number of counts and the radioactivity of the radiation sources. We have found that the two types(the open and closed types with 0.5mm fibers) of fiber sensors show sufficient sensitivities for radioactive concentrations of 0.05, 0.1, 0.2 mCi/mo 3H and 14C. They also show measurable sensitivities for the 14C solution of μCi order. Fairly good proportionalities are found between the total number of counts and the radioactive concentration of the sources. In case of coincidence circuit, has shown good linearities between the radioactivity concentration and the total number of counts for the sensor as long as the non-coincidence is within the measurable limits. But, noise that it was occur at a low channel for non-coincidence measurement remarkably decreased. Both of the method, it is also found that the sensors are about 11-40 times more sensitive to beta rays from 14C than from 3H, and the sensor constructed with 0.5mm fibers has higher sensitivities than the sensor constructed with 1mm fibers
[en] A fiber-optic temperature sensor (FOTS) using an infrared optical fiber was developed and applied to remote and real-time measurements of the temperature of the water in a spent nuclear fuel pool (SNFP) at a nuclear power plant (NPP). In this study, metal caps were employed as the sensing probe of the FOTS owing to their high thermal conductivity. An infrared optical fiber, PIR AgCl:AgBr polycrystalline fiber, was used to transmit the infrared light emitted from the water at a certain temperature. The FOTS was used to measure the temperature of the water in oil bath by changing the temperature in 5 ◦C increments over the range from 30 to 70 ◦C. The temperatures measured by using the FOTS with a metal cap varied almost linearly over that range, which means that the FOTS with a metal cap can be used as an auxiliary monitoring system for measuring the temperature of the water in a SNFP water temperature.
[en] 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 48 h were taken at the principal's and administration office. The radon concentrations at one school, Naenam, exceeded the action level (148 Bq/m3) established by the U.S. EPA, while those at the other two schools were below that level. - Highlights: • Preliminary measurements of the indoor radon concentrations were performed at the auditoriums in 23 elementary schools in Gyeongju. • Considering the geological characteristics and preliminary survey results, three elementary schools were screened for closer scrutiny. • For the three schools, continuous measurements were made at their principal's and administration offices over 48-h period. • The scrutiny revealed one elementary school of high radon concentration much higher than the U.S. EPA action level
[en] The effect of the solution treatment and aging (STA) conditions on the tensile properties of Ti–4 mass%Fe–4 mass%Al–0.25 mass%Si alloy has been investigated in this work. The obtained results revealed that varying the solution temperature affected the stability of the β phase due to the Fe partitioning (which inhibited the β→α′/α″ reaction during water quenching), while the magnitude of the aging temperature determined the predominant products of the β→isothermal ω→secondary αrich→secondary αlean+TiFe phase transformation with distinct tensile characteristics. In addition, the relationship between the alloy microstructure and its tensile properties was discussed.
[en] The most important point of decommissioning nuclear facilities and nuclear power plants is to spend less money and do this process safely. In order to perform a better decommissioning nuclear facilities and nuclear power plants, a data base of radioactive waste from decontamination and decommissioning of nuclear facilities should be constructed. This data base is described herein, from the radioactive nuclide to the shape of component of nuclear facilities, and representative results of the status and analysis are presented. With the increase in number of nuclear facilities at the end of their useful life, the demand of decommissioning technologies will continue to grow for years to come. This analysis of medium-and large-sized radioactive metal wastes and 3D visualization technology of the radioactive metal wastes using the 3D-SCAN are planned to be used for constructing data bases. The data bases are expected to be used on development of the basic technologies for decommissioning nuclear facilities 4 session
[en] A small radiation detection system is necessary for the direct characterization of alpha/beta-ray contamination inside pipes generated during the decommission of a nuclear facility. In this work, the new type phoswich detector consisting of the ZnS(Ag) and plastic scintillator for α/β simultaneous counting was designed as part of a development of a equipment capable of monitoring radiological contamination inside pipes. The optimum counting conditions in dimensions of scintillator and a detection system were experimentally confirmed and a performance of alpha/beta-ray discrimination was evaluated. As a result, optimum conditions of a detector suitable for monitoring radiological contamination inside pipes and a feasibility of application to pipe-inside were confirmed
[en] Remote detecting system for a radiation contamination using a plastic scintillator and an optical fiber was developed. Using a commercially available silica optical fiber and a plastic scintillator, we tested then for a real possibility as a remote monitoring detector. Also, a plastic scintillator was developed by itself, and evaluated as a radiation sensor. The plastic scintillator was made of epoxy resin, a hardener and an organic scintillation material. The mixture rate of the epoxy resin, hardener and organic scintillator was fixed by using their emission spectrum, transmittance, intensity etc. In this study, in order to decrease the light loss of an incomplete connection between an optical fiber and a scintillator, the optical fiber was inserted into the scintillator during the fabrication process. The senor used a plastic optical fiber and was estimated for its detection efficiency by an optic fiber's geometric factor.
[en] Some facilities such as hot-cell are very high radiation level, so it is difficult to approach for radiation monitoring. In this case the detector system is preferable to separate the sensor and electronics, which have to locate in the facility outside to avoid the electric noise and worker's exposure. In this study the detector system applicable to the high-level radioactive contamination of the narrow gap of the installations in the nuclear facilities was developed. The radiation sensor was prepared using a transparent epoxy resin and an inorganic scintillator. The epoxy resin has been used in a wide application field by advantages such as reaction-constriction is very small and no volatility during the hardening process, easiness to manufacture and a high transparency. For signal transmission of the scintillation the optical fiber was used and the epoxy resin easily combined with an optical fiber
[en] Technetium-99m MIBI was developed as a myocardiac perfusion imagine agent and has been used effectively in the detection and post-therapeutic evaluation of various neoplasm such as thyroid, lung, bone and breast tumors. As an infrequent findings, Tc-99m MIBI agent has shown in non-neoplastic pulmonary conditions including fibroding alveolitis, pulmonary actinomycosis, active pulmonary sarcoidosis, pulmonary interstitial fibrosis in progressive systemic sclerosis and active osteomyelitis. In a recent report conducted by Cetin Oncel, Tc-99m MIBI imaging is an effective method in the detection and follow-up of pulmonary tuberculosis. We have also experienced Tc-99m-MIBI uptake in active pulmonary tuberculosis incidentally found in a patient with suspected proliferative villonodular synovitis of the left ankle.
[en] According to the research on the actual condition in Korea, as the field of radiation expands, the number of transport of radioactive materials are increasing day by day. The IAEA is constantly amending and supplementing the standards for transport of radioactive materials based on the latest scientific technology and the data on the health effects of radiation accumulated every so far, however, it is difficult to apply them collectively because there are different acceptable conditions for each country. For actively cope with such international trends and achieve advanced regulation, it is necessary to review the current standards for transport of radioactive materials in domestic and to establish regulations of the radiation protection that reflect characteristics of the radiation environment in domestic. In this study, therefore, to evaluate the validity of the current standards for transport of radioactive materials in domestic, we drew the background and basis of calculation of standards with comparing and analyzing international standards for the dose criteria for transport of radioactive materials. These results can be used as basic data for the improvement of domestic regulations for transport of radiation material