• 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.

• Progress in Medical Physics
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• v.15 no.2
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• pp.59-62
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• 2004

We developed very small parallel plate radiation detector by using our existing experience of mating radiation dosimeter and capability of analyzing characteristics of dosimeter. The radiation detector was consisted of microfilm and carbon electrode. The detector was parallel plate type of all-filled ionization chamber. The ionization chamber had been fabricated using an acrylic plate for the air cavity and carbon coated microfilm for electrical configuration. The alr gap between two electrodes was 0.48 mm. The diameters of collect electrode and guard electrode were 3.3 mm, 5 mm respectively. The diameter of high voltage electrode was 5 mm. Nominal sensitive volume of the chamber was 0.016 ㎤. The major parameters of the chamber characteristics such as leakage current, reproducibility, dose rate effect, and polarity effect were measured. The experimental results were as followings. Leakage current was 0.1 pA. Standard deviation of reproducibility was less than 0.1%. Dose rate effect was less than 1.5%. Polarity effect was less than 2.4%. These data were comparable to those of commercially available dosimetric system for QA-purpose. As the result, we found that the radiation detector consisting of the ionization chamber, microfilm and carbon electrode, was satisfactory for the purpose of the small field dosimetry in size and characteristics. In the future, We will try to refine the dosimeter for use in very small volume.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.29-34
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• 2014

A dosimeter using tissue-equivalent scintillator by photon-counting method was developed and evaluated in its performance. The dosimeter is portable and can be operated by low power from lap-top computer. A data-acquisition software of the dosimeter system was developed by Labwindows/CVI based on Windows. The energy to channel ratio for energy calibration was 0.839 keV/ch. obtained from pulse height spectrum of $^{137}Cs$ and $^{60}Co$ gamma-ray. Using the dosimeter system, the absorbed dose of environmental radiation in Gyungju was 0.18 ${\mu}Sv/h$.

• Journal of Radiation Protection and Research
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• v.25 no.4
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• pp.197-205
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• 2000

A prototype electronic dosimeter(PED) adopting a silicon PIN diode detector as a radiation detector has been developed, manufactured and test-evaluated. A radiation signal processing circuit has been electronically tested and then the radiation detection characteristics of this PED has been performance-tested by using a reference photon radiation field. As a result in a electronic performance test, radiation signals from a detector were well observed in the signal processing circuit. The radiation detection sensitivity of this PED after several test-irradiations to $^{137}Cs$ gamma radiation source appeared to be 1.85 cps/$Gy{\cdot}h^{-1}$ with 19.3% of the coefficient of variation, which satisfied the performance criteria for the active personnel radiation monitor. Further improvement of the electronic circuit and operating program will enable the PED to be used in personal monitoring purpose.

• Progress in Medical Physics
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• v.19 no.1
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• pp.9-13
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• 2008

The purpose of this study was to measure the skin dose using the glass dosimeter and diode and to compare those measurements to the planned skin dose from the treatment planning system. For the reproducibility of the glass dosimeter (ASAHI TECHNO GLASS CIRPORATION, Japan), the same dose was irradiated to 40 glass dosimeters three times, among which 28 with the reproducibility within 3% were selected for the use of this study. For each of 27 breast cancer patients, the glass dosimeters and diodes were attached to 4 different locations on the skin to measure the dose during treatment. All the patients received one fraction of 180 cGy each. The maximum difference of measurements between the glass dosimeter and diode at the same location was 3.2%. Comparing with the planned skin dose from the treatment planning system (Eclipse v6.5, Varian, USA), the dose measured by the glass dosimeter and the diodeshowed on an average 3.4% and 2.3% difference, respectively. The measured doses were always less than the planned skin dose. This may be due to the specific errors of both detectors. Also, the difference may be caused by the fact that since the skin where the detectors were attached is pretty moveable, it was not fix the detectors on the skin.

• Journal of Radiation Protection and Research
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• v.40 no.4
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• pp.261-266
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• 2015

As performance of electronic personal dosimeter (EPD) used for auxiliary personal dosimeter in nuclear power plants (NPPs) has been being continuously improved, we investigated application cases in Korea and other countries and also tested it in NPPs to assess the performance of EPD for external radiation dosimetry. Result of performance tests done in domestic NPPs was similar to those obtained by IAEA in cooperation with EURADOS (IAEA-TECDOC-1564). In addition, EPD/TLD dose ratio has shown similar tendency of EPD/Film-badge dose ratio from the research by the Japan Atomic Power Company (JAPC) and EPD provided more conservative value than TLD or Film-badge. Although some EPD's failures have been discussed, EPD has shown continuous improvement according to the report of Institute of Nuclear Power Operation (INPO) and data from domestic NPPs. In conclusion, It is considered that the general performance of EPD is adequate for external radiation dosimetry compared with that of TLD, providing appropriate performance checking procedure and alternative measures for functional failure.

• 대한방사선방어학회:학술대회논문집
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• 2009.11a
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• pp.74-75
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• 2009

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.51-57
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• 2002

An electronic personal dosimeter(EPD) with hybrid type preamplifier adopting a semiconductor detector as a radiation detector has been developed, manufactured and test-evaluated. The radiation detection characteristics of this EPD has been performance-tested by using a reference photon radiation field. After several test-irradiations to a $^{137}Cs$ gamma radiation source the radiation detection sensitivity of this EPD appeared to be $3.8\;cps/Gy{\cdot}h^{-1}$. The linearity of radiation response was kept within 8% of the dose equivalent ranges of $10{\mu}Sv{\sim}4Sv$ and the angular dependence was under less than 4% in angles of ${\pm}60^{\circ}$. It was confirmed that the energy response range was in $60{\sim}1,250keV$ given in the ISO standard. This EPD satisfied the international criteria for the EPD in the mechanical and the environmental performance test for 9 test categories according to IEC 61526.

• Journal of Sensor Science and Technology
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• v.15 no.2
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• pp.102-105
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• 2006

In-vivo dosimetry is an essential tool of quality assurance programs in radiotherapy. The most commonly used techniques to verify dose are thermoluminescence dosimeter (TLD) and diode detectors. Metal oxide semiconductor field-effect transistor (MOSFET) has been recently proposed for using in radiation therapy with many advantages. The reproducibility, linearity, isotropy, dose rate dependence of the MOSFET dosimeter were studied and its availability was verified. Consequently the results can be used to improve therapeutic planning procedure and minimize treatment errors in radiotherapy.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.79-83
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• 2021

In radiation therapy, electron beam is often used in the treatment of superficial lesion. Accurate measurements are required because electron beam interacts with them in the beam path and affects dose measurements. However, no research has been conducted on electron beam quality assurance. in this study, PbO-based dosimeter was fabricated as a basic study for electron beam quality assurance. Thus, the reproducibility and linearity of the energy of 6, 9, and 12 MeV were analyzed to evaluate measurement accuracy and precision. Reproducibility measurements show RSD value of 1.024%, 1.019% and 0.890%, respectively, at 6, 9, and 12 MeV. linearity measurements show 0.9999 R2 at 6, 9, and 12 MeV altogether. Both evaluations show that the PbO dosimeter has very good measurement accuracy and precision with excellent results.