• Journal of Radiation Protection and Research
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• v.34 no.4
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• pp.176-183
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• 2009

Maintenance on the water chamber of steam generator during outage in nuclear power plants (NPPs) has a likelihood of high radiation exposure to whole body of workers even short time period due to the high radiation exposure rates. In particular, it is expected that hands would receive the highest radiation exposure because of its contact with radiation materials. In this study, characteristic analysis of inhomogeneous radiation fields for contact operations was conducted using thermoluminescent dosimeter (TLD) readouts from the application tests of two-dosimeter algorithm to Korean NPPs in 2004. It is regarded that inhomogeneous radiation fields for contact operations in NPPs are dominated by high energy photons. In addition, field tests for workers who participated in maintenance on the steam generator during outage at Ulchin NPPs in 2009 and pressure tube replacement at Wolsong NPPs in 2009 were conducted to analyze radiation fields and to estimate the extremity dose. As a result, radiation fields were dominated by high energy photons.

• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.67-73
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• 2015

We present a novel method to implement time-delayed propagation of radiation fields in cosmological radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative transfer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.56-63
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• 2024

In high radiation fields, gamma cameras suffer from pulse pile-up, resulting in poor energy resolution, count losses, and image distortion. To overcome this problem, various methods have been introduced to reduce the size of the aperture or pixel, reject the pile-up events, and correct the pile-up events, but these technologies have limitations in terms of mechanical design and real-time processing. The purpose of this study is to develop a real-time gamma camera to evaluate the radioactive contamination in high radiation fields. The gamma camera is composed of a pinhole collimator, NaI(Tl) scintillator, position sensitive photomultiplier (PSPMT), signal processing board, and data acquisition (DAQ). The pulse pile-up is corrected in real-time with a field programmable gate array (FPGA) using the start time correction (STC) method. The STC method corrects the amplitude of the pile-up event by correcting the time at the start point of the pile-up event. The performance of the gamma camera was evaluated using a high dose rate ¹³⁷Cs source. For pulse pile-up ratios (PPRs) of 0.45 and 0.30, the energy resolution improved by 61.5 and 20.3%, respectively. In addition, the image artifacts in the ¹³⁷Cs radioisotope image due to pile-up were reduced.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.216-221
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• 2016

Background: Very fine radiation-induced aerosol particles are produced in intense radiation fields, such as high-intensity accelerator rooms and containment vessels such as those in the Fukushima Daiichi nuclear power plant (FDNPP). Size measurement of the aerosol particles is very important for understanding the behavior of radioactive aerosols released in the FDNPP accident and radiation safety in high-energy accelerators. Materials and Methods: A combined technique using wire screens and imaging plates was developed for size measurement of fine radioactive aerosol particles smaller than 100 nm in diameter. This technique was applied to the radiation field of a proton accelerator room, in which radioactive atoms produced in air during machine operation are incorporated into radiation-induced aerosol particles. The size of $^{11}C$-bearing aerosol particles was analyzed using the wire screen technique in distinction from other positron emitters in combination with a radioactive decay analysis. Results and Discussion: The size distribution for $^{11}C$-bearing aerosol particles was found to be ca. $70{\mu}m$ in geometric mean diameter. The size was similar to that for $^7Be$-bearing particles obtained by a Ge detector measurement, and was slightly larger than the number-based size distribution measured with a scanning mobility particle sizer. Conclusion: The particle size measuring method using wire screens and imaging plates was successfully applied to the fine aerosol particles produced in an intense radiation field of a proton accelerator. This technique is applicable to size measurement of radioactive aerosol particles produced in the intense radiation fields of radiation facilities.

• Journal of Radiation Industry
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• v.17 no.1
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• pp.101-110
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• 2023

Radiation and radioisotopes have a high value in terms of utilization that can be used in convergence with various fields. However, due to the specificity of radiation, the use of radiation and radioisotopes is more difficult than in other industrial fields and also involves complex regulations. There are no clear industrial technology standards in these fields. Therefore, the growth of the radiation industry, especially including small companies, is being delayed. Since industrial technology standards play an important role in providing an institutional basis for the continuous development and settlement of domestic technology, the development of technical standards for the radiation and radioisotope industries can lead to systematic growth of the domestic radiation industry. To this end, the technology classification of the radiation industry was promoted and classified into 7 major categories, and detailed classification was divided according to the characteristics of each technology. In addition, a demand and perception survey on the need for industrial technology standards was conducted on RI licensed institutions and companies, and as a result, 61.4% responded that it was necessary, and in particular, they recognized the need for radiation safety(63.3%). In this paper, the technical classification for the radiation field is presented as the first step in the development of industrial technical standards for the radiation industry. In addition, the plan of the current status information and preparation of standard procedures of each category will be discussed.

• Advances in nano research
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• v.16 no.6
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• pp.579-591
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• 2024

This study explained the effects of radiation, magnetic field, and nanoparticle shape on the peristaltic flow of an Upper-Convected Maxwell nanofluid through a porous medium in an asymmetric channel for a better understanding of cooling and heating mechanisms in the presence of magnetic fields. These phenomena are modeled mathematically as a system of non-linear differential equations, that are solved under long-wavelength approximation and low Reynolds number conditions using the perturbation method. The results for nanofluid and temperature described the behavior of the pumping characteristics during their interaction with (the vertical position, thermal radiation, the shape of the nanoparticle, and the magnetic field) analytically and explained graphically. Also, the combined effects of thermal radiation parameters and some physical parameters on pressure rise, pressure gradient, velocity, and heat distribution are pointed out. Qualitatively, a reverse velocity appears with combined high radiation and Grashof number or combined high radiation and low volume flow rate. At high radiation, the spherical nanoparticle shape has the greatest effect on heat distribution.

• Journal of Radiation Protection and Research
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• v.20 no.3
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• pp.143-154
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• 1995

In recent years, the development of new technologies using static magnetic fields has increased the possibility of human exposure to these fields and raised some concern as to their possible health effects. In several countries, governmental or other competent authorities have issued exposure limits that are mainly intended for specific uses, i.e., magnetic resonance imaging (MRI) and particle accelerators for high-energy Physics. Since applications of magnetic fields in industry and medicine are likely to grow in the future, thus increasing the possibility of occupational and general public exposure, and since the number of people with ferromagnetic implants and implanted electronic devices that can be affected by the fields is growing, there is a need for international guidelines. In the present papers, guidelines on limits of exposure to static magnetic fields are selected and discussed in order to review the guidelines of the International Non-ionizing Radiation Committee of the International Radiation Protection Association (IRPA/INIRC) for non-ionizing radiation(NIR)

• Journal of Radiation Protection and Research
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• v.36 no.4
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• pp.230-236
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• 2011

As a way of improving social receptivity of using radiation, this study looked into the difference of understanding the need of using radiation in various fields between students majoring in radiation and non-radiation related studies, who will influence public opinion in the long term. This study also provides data needed for developing efficient strategies for projects promoting the public's awareness of using radiation. Of the students in the 79 schools sampled, 24%(177) were in 4 year colleges and 146 were junior colleges in educational statistics service (http://cesi.kedi.re.kr) In November 2010 1,945 students were selected as a sample, and they were given surveys on the need of using radiation in different fields. As a result, both between students majoring in radiation and non-radiation related studies showed a high level of understanding the need for radiation in the medical field and showed a low level of understanding of the need for radiation in the agricultural field. In all 6 fields of radiation use, students majoring in radiation related studies showed higher levels of understanding for the need to use radiation than students majoring in radiation and non-radiation related studies. In each field, male students and those who have experience medical radiation and relevant education had higher level of understanding. This shows we need to improve the understanding of the cases of female students and those who have not had experiences with medical radiation and to provide relevant education through various kinds of information. The characteristics of the groups that are shown in the results of this study are considered to be helpful for efficiently for project promoting the public's awareness of using radiation.

• Journal of Radiation Industry
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• v.11 no.3
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• pp.123-130
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• 2017

Concerns about high radiation exposure to the hands of radiation workers who may contact with radioactive contamination on surfaces in a nuclear power plant (NPP) had been raised, and the Korean regulatory body required the extremity dose estimation during contact tasks with radioactive materials. Korean NPPs conducted field tests to identify the incident radiation to the hands of radiation workers who may contact with radioactive contamination during maintenance periods. The results showed that the radiation fields for contact tasks are dominated by high energy photons. It was also found that the radiation doses to the hands of radiation workers in Korean NPPs were much less than the annual dose limits for extremities. This approach can be applicable to measure and estimate the extremity dose to the hands of medical workers who handle the radioactive materials in a hospital.

• Journal of Radiation Protection and Research
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• v.20 no.1
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• pp.53-64
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• 1995

The radiation fields following the large loss of coolant accident (LOCA) have been assessed for the vital areas in the service building of Wolsong 2, 3, and 4 nuclear power plants. The ORIGEN2 code was used in calculating the fission product inventories in the fuel. The source terms were based upon the activity released following the dual failure accident scenario, i.e., a LOCA followed by impaired emergency core cooling (ECC). Configurations of the reactor building, the service building, and the ECC system were constructed for the QAD-CG calculations. The dose rates and the time-integrated doses were calculated for the time period of upto 90 days after the accident. The results showed that the radiation fields in the vital access areas were found to be sufficiently low. Some areas however showed relatively high radiation fields that may require limited access.