• Journal of Radiation Protection and Research
• /
• v.34 no.2
• /
• pp.69-75
• /
• 2009

To obtain precise information about characteristics of gamma ray detector system responses, we developed new GUI computer program to analize full-energy absorption peak using our developed Delphi computer code for educational purpose. By use of the well known 4 nonlinear peak shaping functions, peaks were fitted with least square fit method in this code. In this paper, we described the methods to search for 12 coefficients in above 4 nonlinear peak shaping functions by use of our developed code in details. The computer code was tested for 1 $\mu$Ci $^{137)Cs$ 661 keV gamma ray peak spectrum detected by 25 % relative efficiency HPGe detector with 5.35 cm (D) $\times$ 5.5 cm (L) size.

• Journal of Radiation Protection and Research
• /
• v.19 no.2
• /
• pp.121-132
• /
• 1994

This study concerns about the measurement and the investigation of environmental radiation characteristics which the components and the distribution of exposure rates by terrestrial y-rays in Taegu area. $4^{'}{\phi}{\times}4^{'}$ NaI(T1) scintillation detector with a multichannel analyzer was used in the measurement of y-rays as a part of in-situ spectrometry at twenty eight different locations in this area. The conversion into the exposure rate from the measured ${\gamma}-ray$ spectrum has been carried out leading to a net exposure rate and component ones by $^{40}K,\;^{238}U$ series and $^{232}Th$ series products which are known by the major parts in the terrestrial ${\gamma}-rays$ generally. As a result, the average exposure rate by the terrestrial ${\gamma}-rays$ in Taegu area is $9.4{\mu}R/h$ and the distribution of individual exposure rates shows more or less differences between these locations even after the consideration of diurnal and yearly variations which are always involved in these measurements. The component parts of exposure rates are distributed $^{40}K\;2.9{\sim}4.6{\mu}R/h,\;^{238}U$ series $1.2{\sim}3,\;1{\mu}R/h,\;^{232}Th$ series $2.5{\sim}5.0{\mu}R/h$ over the measured locations.

• Journal of Radiation Protection and Research
• /
• v.31 no.3
• /
• pp.149-153
• /
• 2006

An ionization chamber is still widely used in many fields by virtue of its' simple operational characteristics and the possibility of its' various shapes. A parallel type of an ionization chamber for a steel sheet thickness measurement was designed and fabricated. High pure xenon gas, which was pressurized up to 6 atm, was chosen as a filling gas to increase the current response and sensitivity for a radiation. A high pressure gas system was also constructed. The active volume and the incident window size of the fabricated ionization chamber were $30\;cm^3\;and\;12\;cm^2$, respectively. Preliminary tests with a 25 mCi $^{241}Am$ gamma-ray source and evaluation tests in a standard X-ray field were performed. The optimal operation voltage was set from the results of the collection efficiency calculation by using an experimental two-voltage method. Linearity for a variation of the steel sheet thickness, which is the most important factor for an application during a steel sheet thickness measurement, was 0.989 in this study.

• Journal of Radiation Protection and Research
• /
• v.21 no.4
• /
• pp.263-271
• /
• 1996

The ANSI N13.32 recommends that a study of the angular response of a dosimeter be carried out once, although no pass/fail criterion is given for angular response. Gamma dose equivalent conversion and angular dependence factors were calculated by using MCNP code for the case of ANSI N13.32 extremity phantoms(finger and arm) at the depth of $7mg/cm^2$. Those extremity dosimeters were assumed to be irradiated from both monoenergitic photons and ISO X-ray narrow beams. These calculated gamma dose equivalent conversion and angular dependence factors were compared to B. Grosswendt's result calculated by using X-ray beams. The result showed that the dose equivalent conversion factors of this study agreed well with that of B. Grosswendt for all energies within 2% except 7% in the case of the low energies. In the case of angular dependence factors comparison, they agreed within 3%. It was shown that angular dependence factors of the finger phantom decreased as the horizontal angle of the phantom increased for the ISO X-ray beams less than 60keV. For the higher energy X-ray beams range they decreased slightly around 40 degree, but then increased from this energy to 90 degree.

• Journal of Radiation Protection and Research
• /
• v.48 no.4
• /
• pp.167-174
• /
• 2023

Background: A nondestructive test is commonly used to inspect the surface defects and internal structure of an object without any physical damage. X-rays generated from an electron accelerator or a tube are one of the methods used for nondestructive testing. The high penetration of X-rays through materials with low atomic numbers makes it difficult to discriminate between these materials using X-ray imaging. The interaction characteristics of neutrons with materials can supplement the limitations of X-ray imaging in material discrimination. Materials and Methods: The radiation image acquisition process for air-cargo security inspection equipment using X-rays and neutrons was simulated using a GEometry ANd Tracking (Geant4) simulation toolkit. Radiation images of phantoms composed of 13 materials were obtained, and the R-value, representing the attenuation ratio of neutrons and gamma rays in a material, was calculated from these images. Results and Discussion: The R-values were calculated from the simulated X-ray and neutron images for each phantom and compared with those obtained in the experiments. The R-values obtained from the experiments were higher than those obtained from the simulations. The difference can be due to the following two causes. The first reason is that there are various facilities or equipment in the experimental environment that scatter neutrons, unlike the simulation. The other is the difference in the neutron signal processing. In the simulation, the neutron signal is the sum of the number of neutrons entering the detector. However, in the experiment, the neutron signal was obtained by superimposing the intensities of the neutron signals. Neutron detectors also detect gamma rays, and the neutron signal cannot be clearly distinguished in the process of separating the two types of radiation. Despite these differences, the two results showed similar trends and the viability of using simulation-based radiation images, particularly in the field of security screening. With further research, the simulation-based radiation images can replace ones from experiments and be used in the related fields. Conclusion: The Korea Atomic Energy Research Institute has developed air-cargo security inspection equipment using neutrons and X-rays. Using this equipment, radiation images and R-values for various materials were obtained. The equipment was reconstructed, and the R-values were obtained for 13 materials using the Geant4 simulation toolkit. The R-values calculated by experiment and simulation show similar trends. Therefore, we confirmed the feasibility of using the simulation-based radiation image.

• Journal of Radiation Protection and Research
• /
• v.37 no.1
• /
• pp.16-24
• /
• 2012

In the present study, a gamma-ray detector and associated signal processing circuit was developed for a side-absorber of a dual-mode Compton camera. The gamma-ray detector was made by optically coupling a CsI(Tl) scintillation crystal to a silicon photodiode. The developed signal processing circuit consists of two parts, i.e., the slow part for energy measurement and the fast part for timing measurement. In the fast part, there are three components: (1) fast shaper, (2) leading-edge discriminator, and (3) TTL-to-NIM logic converter. AC coupling configuration between the detector and front-end electronics (FEE) was used. Because the noise properties of FEE can significantly affect the overall performance of the detection system, some design criteria were presented. The performance of the developed system was evaluated in terms of energy and timing resolutions. The evaluated energy resolution was 12.0% and 15.6% FWHM for 662 and 511 keV peaks, respectively. The evaluated timing resolution was 59.0 ns. In the conclusion, the methods to improve the performance were discussed because the developed gamma-ray detection system showed the performance that could be applicable but not satisfactory in Compton camera application.

• Journal of Radiation Protection and Research
• /
• v.20 no.2
• /
• pp.97-102
• /
• 1995

Adaptive response induced by low dose ${\gamma}-ray$ irradiation in human peripheral lymphocytes was examimed. Human lymphocytes were exposured to low dose of ${\gamma}-ray$ (priming dose, 0.01Gy) followed by high dose (challenging dose, 1.5Gy) after various time intervals (4, 7, 20 hours). Frequencies of micronuclei were enumerated in both primed and unprimed groups. Maximum reduction in frequency of micronuclei was observed when challenging dose irradiation was followed by priming dose after 4hr incubation period. When challenging doses were irradiated 7 or 20hr after priming dose, frequencies of micronuclei were reduced slighty. However, these reduction were not statistically significant. In this study, human peripheral lymphocytes were irradiated at Go phase and they showed adaptive response induced by low dose radiation. Since micronucleus assay is relatively simpler and faster than other methods, it may be a good tool for evaluating radiation-induced adaptive responses.

• Journal of Radiation Protection and Research
• /
• v.35 no.1
• /
• pp.21-25
• /
• 2010

Burnup of spent fuel should be determined accurately for the safety control of spent fuel. Especially, it is necessary to measure the burnup profile along the nuclear fuel axis. In the present work, an ionization chamber was designed and fabricated to measure the gamma ray profile inside the guide tube of spent fuel. The ionization chamber was composed of three parts; induction part, gas-inlet part, and sensor part. The sensor part had two electrodes; cathode and anode. A guide electrode was considered in the ionization chamber design to make the ionization chamber to be inserted easily into the guide tube. Pure gas (argon and xenon) was inserted into the ionization chamber, and the leakage current and saturation curve were measured to determine the operation characteristics of the ionization chamber. The gamma ray radiation was also measured in relatively high dose environment. The gamma ray profile of the spent fuel will be measured with the ionization chamber.

• Journal of Radiation Protection and Research
• /
• v.34 no.3
• /
• pp.107-114
• /
• 2009

A Compton camera, which is based on Compton kinematics, is a very promising gamma-ray imaging device in that it could overcome the limitations of the conventional gamma-ray imaging devices. In the present study, the image quality of a rotating Compton camera was evaluated by using 4-D Monte Carlo simulation technique and the applicability to nuclear industrial applications was examined. It was found that Compton images were significantly improved when the Compton camera rotates around a gamma-ray source. It was also found that the 3-D imaging capability of a Compton camera could enable us to accurately determine the 3-D location of radioactive contamination in a concrete wall for decommissioning purpose of nuclear facilities. The 4-D Monte Carlo simulation technique, which was applied to the Compton camera fields for the first time, could be also used to model the time-dependent geometry for various applications.

• Journal of Radiation Protection and Research
• /
• v.47 no.1
• /
• pp.16-21
• /
• 2022

Background: Epidemiological observations such as mental retardation, physical deformities, etc., in children besides different types of cancer in the adult population of the Malwa region have been reported. The present study is designed to get insight into the role of naturally occurring radioactive material (NORM) in causing detrimental health effects observed in the general population of this region. Materials and Methods: Deep soil samples were collected from different locations in the Malwa region. Their activity concentrations were determined using low-level background gammaray spectrometry. High efficiency and high purity germanium detector capped in a lead-shielded chamber having a resolution of 1.8 keV at 1,173 keV and 2.0 keV at the 1,332 keV line of ⁶⁰Co was used in the present work. Data were evaluated with Genie-2000 software. Results and Discussion: Mean activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in deep soil were found to be 101.3 Bq/kg, 65.8 Bq/kg, and 688.6 Bq/kg, respectively. The mean activity concentration of ²³⁸U was found to be three and half times higher than the global average prescribed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). It was further observed that the activity concentration of ²³²Th and ⁴⁰K has a magnitude that is nearly one and half times higher than the global average prescribed by UNSCEAR. In addition, the radioisotope ¹³⁷Cs which is likely to have its origin in radiation fallout was also observed. It is postulated that the NORM present in high quantity in deep soil somehow get mobilized into the water aquifers used by the general population and thereby causing harmful health problems. Conclusion: It can be stated that the present work has been able to demonstrate the use of low background gamma-ray spectrometry to understand the role of NORM in causing health-related effects in a general population of the Malwa region of Punjab, India.