• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1035-1039
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• 2010

Activation products generated by photoneutrons in concrete shielding wall around electron linac were estimated for a high energy X-ray container cargo inspection system. Monte carlo code, MCNPX2.5.0 was used for reference system of 9MeV fixed type dual-direction container cargo inspection system installed at major harbors in Korea. Activation products inventory generated by photoneutron (n,$\gamma$) reaction are estimated, and then radiation dose rate is calculated from the results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3412-3418
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• 2013

The Purpose of this study was to evaluate by comparing the dose change and build up characteristic according to delay time in 30 days of glass dosimeter processed preheat and non preheat when measuring accumulation dose of radiation by using glass dosimeter over the long haul. For obtaining low dose with 0.1 mGy, 1 mGy and 5 mGy, we employed diagnostic generator AccuRay-650R. We compared the build up characteristic over the long haul by exposuring radiation to 30 glass dosimeters sorted into 10 glass dosimeters per tube voltage and current. In Non preheat glass dosimeter, initial measured dose was inferior to exposed dose but as time goes on, was close to exposed dose steadily. In 72 hour after experiment end, non preheat glass dosimeters were not indicated the difference from preheat glass dosimeters and statistical analysis were meaningful (p>0.05). Initial measured dose for low glass dosimeter processed preheat was close to exposed dose and stable. After 15 days dose was gradually increased. Previous study characteristics of glass dosimeter were with respect to characteristic of glass dosimeter in high dose of high energy area. However, in this study, we make a judgment to measure the dose of glass dosimeter without preheat processing when measuring the accumulation dose of low dose in conclusion.

• Journal of Radiation Protection and Research
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• v.24 no.4
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• pp.205-213
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• 1999

Effective dose conversion coefficients from unit activity radionuclides contaminated on the ground surface were calculated by using MCNP4A rode and male/female anthropomorphic phantoms. The simulation calculations were made for 19 energy points in the range of 40 keV to 10 MeV. The effective doses E resulting from unit source intensity for different energy were compared to the effective dose equivalent $H_E$ of previous studies. Our E values are lower by 30% at low energy than the $H_E$ values given in the Federal Guidance Report of USEPA. The effective dose response functions derived by polynomial fitting of the energy-effective dose relationship are as follows: $f({\varepsilon})[fSv\;m^2]=\;0.0634\;+\;0.727{\varepsilon}-0.0520{\varepsilon}^2+0.00247{\varepsilon}^3,\;where\;{\varepsilon}$ is the gamma energy in MeV. Using the response function and the radionuclide decay data given in ICRP 38, the effective dose conversion coefficients for unit activity contamination on the ground surface were calculated with addition of the skin dose contribution of beta particles determined by use of the DOSEFACTOR code. The conversion coefficients for 90 important radionuclides were evaluated and tabulated. Comparison with the existing data showed that a significant underestimates could be resulted when the old conversion coefficients were used, especially for the nuclides emitting low energy photons or high energy beta particles.

• Journal of Radiation Protection and Research
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• v.37 no.4
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• pp.191-196
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• 2012

A double-scattering type Compton camera which is appropriate to imaging a high-energy gamma source has been developed for nuclear material surveillance at Hanyang University. The double-scattering type Compton camera can provide high imaging resolution; however, it has disadvantage of relatively low imaging sensitivity than existing single-scattering type Compton camera. In this study, we introduce a novel concept of a dual-mode Compton camera which incorporates two different types of Compton camera, i.e., single- and double-scattering type. The dual-mode Compton camera can operate high-resolution mode and high-sensitivity mode in a single system. To maximize its performance, the geometrical configuration was optimized by using Geant4 Monte Carlo simulation toolkit. In terms of imaging sensitivity, high-sensitivity mode had higher sensitivity than high-resolution mode up to 100 times while high imaging resolution of the double-scattering Compton camera was maintained.

• Progress in Medical Physics
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• v.13 no.4
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• pp.229-233
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• 2002

We have tested a combined CT/SPECT system with a single CZT detector for x-ray and gamma-ray medical imaging. The size of detector is 10$\times$10$\times$5 ㎣, and the anodes are pixellated as a 4$\times$4 array with a pixel dimension of $1.5\times$1.5 $\textrm{mm}^2$. The cathode was coated with a continuous Au-plated. We have characterized the system performance by scanning a radiographic resolution phantom and the Hoffman Brain phantom. Pulse counting electronics with very short shaping time (50 ㎱) are used to satisfy high photon rates in x-ray imaging, and response linearity up to 3$\times$10$^{5}$ counts per second per detector element is achieved. Energy resolution of 10.4% and 5.3% FWHM at Tc-99m 140 keV peak are obtained for the 50 ㎱ and 2 $mutextrm{s}$ shaping times, respectively. The spatial resolutions of CT and SPECT are about 1mm and 9mm, respectively. Photopeak efficiency of detector systems are 41.0% for 50㎱ and 72.5% for 2 $mutextrm{s}$ shaping time.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.545-552
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• 2002

In order to investigate the influence of nuclear power plant operation on its nearby environment, soil, stream and marine sediment samples were collected in the vicinity of the Youngkwang Nuclear Power Plant in Korea, and analyzed for artificial and natural radionuclide radioactivity. From the analytical result, Cs-137 was detected in most soil samples. but it may have been derived fiom past nuclear weapon tests because Cs-134 having short half-live was not detected. The radioactivities of Cs-137 in the sediment samples were also detected which are within the normal range in the sediments based upon the published literature between 1997 and 1999. For the quality control of radioactivity analysis of environmental samples, sets of marine sediments in the Gamami area were analyzed using two HPGe Gamma-ray Spectroscopes (30% and 45%) according to the geostatistical sampling strategy, and Cs-137 and K-40 results were interpreted by analysis of variance (ANOVA). In the two-way ANOVA, variances derived from the geochemical variation were significant, but errors from sampling and analytical procedures are negligible. In conclusion. all the radioanalytical procedures of this study including sampling are validated to be acceptable.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Korean Journal of Remote Sensing
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• v.12 no.1
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• pp.1-16
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• 1996

Korea Aerospace Research Institute(KARI) is developing a Korea Multi-Purpose Satellite I(KOMPSAT-I) which accommodates Electro-Optical Camera(EOC), Ocean Color Imager(OCI), Space Physics Sensor(SPS) for cartography, ocean color monitoring, and space environment monitoring respectively. The satellite has the weight of about 500 kg and is operated on the sun synchronized orbit with the altitude of 685km, the orbit period of 98 minutes, and the orbit revisit time of 28days. The satellite will be launched in the third quarter of 1999 and its lifetime is more than 3 years. EOC has cartography mission to provide images for the production of scale maps, including digital elevation models, of Korea from a remote earth view in the KOMPSAT orbit. EOC collects panchromatic imagery with the ground sample distance(GSD) of 6.6m and the swath width of 15km at nadir through the visible spectral band of 510-730 nm. EOC scans the ground track of 800km per orbit by push-broom and body pointed method. OCI mission is worldwide ocean color monitoring for the study of biological oceanography. OCI is a multispectral imager generating 6 color ocean images with and <1km GSD by whisk-broom scanning method. OCI is designed to provide on-orbit spectral band selectability in the spectral range from 400nm to 900nm. The color images are collected through 6 primary spectral bands centered at 443, 490, 510, 555, 670, 865nm or 6 spectral bands selected in the spectral range via ground commands after launch. SPS consists of High Energy Particle Detector(HEPD) and Ionosphere Measurement Sensor(IMS). HEPD has mission to characterize the low altitude high energy particle environment and to study the effects of radiation environment on microelectronics. IMS measures densities and temperature of electrons in the ionosphere and monitors the ionospheric irregularities in KOMPSAT orbit.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.4
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• pp.318-323
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• 1981

This study was conducted to establish an effective radiation treatment and selection method for induced mutants in M_1 population of soybean treated with gamma-ray. About 64% of total M_1 plants was reduced in plant height up to 50 - 60% and among which 60 - 70% of the plants were contained mutations in M_2 generation. About 60% of the MI plants have born 6 - 15 seeds per plant and 50 - 60% of their progenies produced mutants in M_2 generation. Positive correlation between plant height and number of seeds per plant in M_1 population was found. Higher visible macro-mutation rate in M_2 was observed in the groups of reduced plant height and seed number in the M_1 generation, whereas the frequency of chlorophyll mutation was increased in the group of less damaged plants. The size of mutation sector was increased with reduction in number of seeds per M_1 plant and the mutants were occurred at random in all the parts of M_1 plants. For the effective selection of mutants in soybean mutation breeding, the M_1 seeds should be harvested from the radiation damaged M_1 plants with the application of higher doses of mutagens, and handling M_2 generation by bulk population method is recommendable.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.225-232
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• 1994

Purpose : This study was to obtain the basic dosimetric data using the 10 MV X-ray for the total body irradiation. Materials and Methods : A linear accelerator photon beam is planned to be used as a radiation source for total body irradiation (TBI) in Chonnam University Hospital. The planned distance from the target to the midplane of a patient is 360cm and the maximum geometric field size is 144cm x 144cm. Polystyrene phantom sized $30{\times}30{\times}30.2cm^3$ and consisted of several sheets with various thickness, and a parallel plate ionization chamber were used to measure surface dose and percent depth dose (PDD) at 345cm SSD, and dose profiles. To evaluate whether a beam modifier is necessary for TBI, dosimetry in build up region was made first with no modifier and next with an 1cm thick acryl plate 20cm far from the polystyrene phantom surface. For a fixed sourec-chamber distance, output factors were measured for various depth. Results : As any beam modifier was not on the way of radiation of 10MV X-ray, the $d_{max}$ and surface dose was 1.8cm and $61\%$, respectively, for 345cm SSD. When an 1cm thick acryl plate was put 20cm far from polystyrene phantom for the SSD, the $d_{max}$ and surface dose were 0.8cm and $94\%$, respectively. With acryl as a beam spoiler, the PDD at 10cm depth was $78.4\%$ and exit dose was a little higher than expected dose at interface of exit surface. For two-opposing fields for a 30cm phantom thick phantom, the surface dose and maximum dose relative to mid-depth dose in our experiments were $102.5\%$ and $106.3\%$, respectively. The off-axis distance of that point of $95\%$ of beam axis dose were 70cm on principal axis and 80cm on diagonal axis. Conclusion: 1. To increase surface dose for TBI by 10MV X-ray at 360cm SAD, 1cm thick acrylic spoiler was sufficient when distance from phantom surface to spoiler was 20cm. 2. At 345cm SSD, 10MV X-ray beam of full field produced a satisfiable dose uniformity for TBI within $7\%$ in the phantom of 30cm thickness by two-opposing irradiation technique. 3. The uniform dose distribution region was 67cm on principal axis of the beam and 80cm on diagonal axis from beam axis. 4. The output factors at mid-point of various thickness revealed linear relation with depth, and it could be applicable to practical TBI.