• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1351-1358
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• 2017

In this work, we investigated radiation hardness of GaN-based transistors which are strong candidates for next-generation power electronics. Field effect transistors with three types of gate structures including metal Schottky gate, recessed gate, and p-AlGaN layer gate were fabricated on AlGaN/GaN heterostructure on Si substrate. The devices were irradiated with energetic protons and alpha-particles. The irradiated transistors exhibited the reduction of on-current and the shift of threshold voltage which were attributed to displacement damage by incident energetic particles at high fluence. However, FET operation was still maintained and leakage characteristics were not degraded, suggesting that GaN-based FETs possess high potential for radiation-hardened electronics.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.13-22
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• 2023

As an alternative to environmental pollution generated from fossil fuels currently in use, research is being actively conducted to use hydrogen that does not cause air pollution. As fire and explosion accidents caused by hydrogen leakage have occurred until recently, research on safety is needed to commercialize hydrogen on ships, which are special environments. In this study, a seasonal alternative scenario for each season and the worst scenario were assumed in the event of a leakage accident while a hydrogen fuel cell propulsion ship equipped with a hydrogen storage tank was navigating at JangSaengPo port in Ulsan. In order to consider environmental variables, the damage impact range was derived through ALOHA and probit analysis based on the annual average weather data for 2021 by the Korea Meteorological Administration and on geographic information data from the National Statistical Office. Radiation showed a wider damage range than that of Overpressure and Flame in both the alternative and worst-case scenarios, and as a result of probit analysis, a fatality rate of 99% was confirmed in all areas.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1927-1934
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• 2016

In this paper, we proposed a I-gate n-MOSFET (n-type Metal Oxide Semiconductors Field Effect Transistor) structure in order to mitigate a radiation-induced leakage current path in an isolation oxide interface of a silicon-based standard n-MOSFET. The proposed I-gate n-MOSFET structure was designed by using a layout modification technology in the standard 0.18um CMOS (Complementary Metal Oxide Semiconductor) process, this structure supplements the structural drawbacks of conventional radiation-tolerant electronic device using layout modification technology such as an ELT (Enclosed Layout Transistor) and a DGA (Dummy Gate-Assisted) n-MOSFET. Thus, in comparison with the conventional structures, it can ensure expandability of a circuit design in a semiconductor-chip fabrication. Also for verification of a radiation-tolerant characteristic, we carried out M&S (Modeling and Simulation) using TCAD 3D (Technology Computer Aided Design 3-dimension) tool. As a results, we had confirmed the radiation-tolerant characteristic of the I-gate n-MOSFET structure.

• Journal of Radiation Protection and Research
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• v.34 no.2
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• pp.77-81
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• 2009

An Area Radiation Monitoring System (ARMS) ionization chamber, which had an 11.8 L active volume, was fabricated and performance-tested at KAERI. Low leakage currents, linearities at low and high dose rates were achieved from performance tests. The correlation coefficients between the ionization currents and the dose rates are 1 at high dose rate and 0.99 at low dose rate. In this study, an integration-type ARMS ionization chamber was tested over a year for an evaluation of its long-term stability at a radioisotope (RI) repository of the Young-gwang nuclear power plant. The standard deviation of dose rate of 1 day data and over a 100-days mean value were 6.2 $\mu$R/h and 2.9 $\mu$R/h, respectively. The fabricated ARMS ionization chamber showed stable performance from the results of the long-term tests. Design and performance characteristics of the fabricated ionization chamber for the ARMS from performance-tests are also addressed.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.39-44
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• 1997

Bulk type radiation detector of Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure using Cd$_{1-x}$ Zn$_{x}$Te(x=20%) wafer(3x4xl mm$^{3}$) grown by high pressure Bridgman method has been developed. We etched wafer surfaces with 2% Br-methanol solution and coated gold thin film on the surfaces by electroless deposition method for 5 min. in 49/o HAuCI$_{3}$ 4H20 solution. Initial etch rates of Cd, Zn and Te were 46%, 12% and 42% respectively. After etched, the surface of wafer was slightly revealed to Te rich condition. The leakage current was increased with etch time, but it didn't exceed 3nA at 50volt. The thickness of Au film was about 100nm by Rutherford Backscattering Spectroscopy(RBS). The resolution were 6.7% for 22.1 keV photon from 109 $^{109}$ Cd and 8.2% for 59.5 keV photon from $^{241}$ Am. The radiation detector such as Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure was more effective to monitor the low energy gamma radiation.iation.

• Journal of Radiation Protection and Research
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• v.44 no.4
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• pp.156-160
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• 2019

Background: To compare the dose of radiation received by the fetus in a pregnant patient irradiated for head and neck cancer using helical tomotherapy and three-dimensional conformal radiation therapy (3DCRT). Materials and Methods: The patient was modeled with a humanoid phantom to mimic a gestation of 26 weeks. Radiotherapy with a total dose of 2 Gy was delivered with both tomotherapy (2.5 and 5.0 cm jaw size) and 3DCRT. The position of the fetus was predicted to be 45 cm from the field edge at the time of treatment. The delivered dose was measured according to the distance from the field edge and the fetus. Results and Discussion: The accumulated dose to the fetus was 1.6 cGy by 3DCRT and 2 and 2.3 cGy by the 2.5 and 5 cm jaw tomotherapy plans. For tomotherapy, the fetal dose with the 2.5 cm jaw was lower than that with the 5 cm jaw, although the radiation leakage was greater for 2.5 cm jaw plan due to the 1.5 fold longer beam-on time. At the uterine fundus, tomotherapy with a 5 cm jaw delivered the highest dose of 2.4 cGy. When the fetus moves up to 35 cm at the 29th week of gestation, the resultant fetal doses for 3DCRT and tomotherapy with 2.5 and 5 cm jaws were estimated as 2.1, 2.7, and 3.9 cGy, respectively. Conclusion: For tomotherapy, scattering radiation was more important due to the high monitor unit values. Therefore, selecting a smaller jaw size for tomotherapy may reduce the fetal dose. however, evaluation of risk should be individually performed for each patient.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.486-492
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• 2015

Radiation source imaging system is essential for protecting of radiation leakage accidents and minimizing damages from the radioactive materials, and is expected to play an important role in the nuclear plant decommissioning area. In this study, the stereoscopic camera principle was applied to develop a new radiation imaging device technology that can extract the radiation three-dimensional position information. This radiation three-dimensional imaging device (K3-RIS) was designed as a compact structure consisting of a radiation sensor, a CCD camera, and a pan-tilt only. It features the acquisition of stereoscopic radiation images by position change control, high-resolution detection by continuous scan mode control, and stereoscopic image signal processing. The performance analysis test of K3-RIS was conducted for a gamma-ray source(Cs-137) in radiation calibration facility. The test result showed that a performance error with less than 3% regardless of distances of the objects.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.825-833
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• 2018

In this study, one calculated the range of damage to the combustion characteristics according to the composition of LNG and the size of leaking holes, and analyzed the damage effect in case of leakage accidents caused by pipe damage in the re-gasification process for the LNG supply system. In order to confirm the combustion characteristics according to LNG composition, there was no significant difference in the result of risk analysis by LNG-producing areas. However, the higher the methane content of the components, the lower the risk of flash fire, hazardous areas of overpressure due to explosion, and thermal radiation damage caused by jet fire. In addition, one investigated the effect of leakage, holes, and ruptures on the risk range and explosions according to the size of the pipe-leakage hole. Also, the influence of overpressure and the range of damage from radiant heat could be predicted. One confirmed the effect of LNG composition and pipe-leakage size on fire and explosion.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.351-358
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• 2018

In this study, we propose a method of suppressing the leakage noise signal of motor assembly through the test. The motor assembly is mounted on outside of the aircraft to rotate an antenna and must satisfy RE102 requirement on MIL-STD-461F in terms of electromagnetic interference. It is confirmed by RE102 test result hat the leakage noise signal of the equipment occurs due to external influx through the power and control cable and rotation of the motor. And it is ascertained that the part where internal/external physical shielding is difficult to rotate is the leakage path. To reduce the leakage noise signal, the electrical ground reinforcement and the electric shielding structure considering the operation of the equipment is applied and it is verified that the requirement is satisfied. Finally, we verified that required specification are met by applying circular corrugated choke with interlocking shapes and conductive grease to the noise leakage path.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.111-115
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• 2007

A deuterium oxide leakage accident occurred on October 4, 1999, at nuclear power plant in Korea. The concentration of tritium in air increased and 22 workers were exposed by tritium at that time. It is well known that tritium causes internal exposure. Therefore, we examined complete blood cell count, physical and biological dosimetry fur 13 workers among whole 22 workers to check the health effect and to evaluate the dose estimation of tritium exposure. The leukocyte count test, one of general blood test, was normal. The estimated doses were 0 - 4.44 mSv by physical dosimetry and 0-37 mGy by biological dosimetry. This dose does not exceed radiation dose limit, and the clinical symptoms of the exposed workers were not shown. The consistency between clinical sign and estimated dose means that physical and biological dosimetry were very useful especially in accident evaluation.