• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.927-934
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• 2002

The HANARO ( High-flux Advanced Neutron Application Reactor) has been operated since 1995. The Cold Neutron (CN) hole was implanted in the reflector tank from the design stage. Before a vacuum chamber and a moderator cell for the cold neutron source are installed into the CN hole, it is necessary to measure exactly the size of the inside diameter and thickness of the CN hole to prevent the interference problem. Due to inaccessibility and high radiation field in the CN hole, a mechanical measurement method is not permitted. The immersed ultrasonic technique is considered as the best way to measure the thickness and the diameter of the CN hole. The 4-Axis manipulator was designed and fabricated for locating the ultrasonic sensors. The transducer of an ultrasonic sensor having 10 MHz frequency leads to high resolution as much as 0.03mm. The inside diameter and thickness of 550 points of the CN hole were measured using 2 channel ultrasonic sensors. The results show that the thickness and inside diameter of the CN hole is in the range of 3.3∼6.7mm and 156∼ 165mm, respectively. This data will be a good reference for the design of the cold neutron source facility.

• Economic and Environmental Geology
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• v.9 no.3
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• pp.135-141
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• 1976

The gamma-gamma logging method appplying in geophysical research are presented in this paper_ The logging probe assembly was designed which permits changing the source-to-detector spacing while conditions of proceeding ${\gamma}-{\gamma}$ logging, which a collimated gamma ray source ($^{60}Co$, 0.5mCi and/or 2 mCi) is separated from the scintillation detector as shown in Fig. 2 and 3, size is 6.0 cm in diameter and 120.0 cm in long and the exposed parts are made of stainless steel pipe. The results is confirmed by the experiment performed mainly in granite rock where a slightly constant shape was obtained but sometimes was shown sharpness shape for the measured scattered gamma-ray intensity. Consequently, the experimental results are obtained an adequate intensity of scattered gamma-rays and favourable response to density change, and also very closely correspond to between core samples of the test boring and to used this method of ${\gamma}-{\gamma}$ logging in the test bore-hole of the strata.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.915-920
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• 2001

A spent fuel problem has prevented the nuclear power from claiming to be a completely clean energy source. The nuclear transmutation technology to incinerate the long lived radioactive nuclides and produce energy during the incineration process is believed to be one or the best solutions. HYPER(Hybrid Power Extraction Reactor) is the accelerator driven transmutation system which is being developed by KAERI(Korea Atomic Energy Research Institute). Some major feature of HYPER have been developed and employed. On-power fueling concepts are employed to keep system power constant with minimum variation of accelerator power. A hollow cylinder-type metal fuel is designed for the on-line refueling concept. Lead-bismuth(Pb-Bi) is adopted as a coolant and Spallation target material. HYPER is a subcritical reactor which needs an external neutron source. 1GeV proton beam is irradiated to Lead-bismuth(Pb-Bi) target inside HYPER, and spallation neutrons are produced. When proton beams are irradiated, much heat is also deposited in the Pb-Bi target and beam window which separates Pb-Bi and accelerator vacuum. Therfore, an effective cooling is needed for HYPER target. In this paper, we performed the thermal-hydraulic analysis of HYPER target using FLUENT code, and also calculated thermal and mechanical stress of the beam window using ANSYS code.

• Publications of The Korean Astronomical Society
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• v.16 no.1
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• pp.31-36
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• 2001

We present the characteristics of the 2K CCD camera at the Bohyunsan Optical Astronomy Observatory of the Korea Astronomy Observatory at the time of its development. The purpose of this paper is to support the observers who may need detailed information on the characteristics of the camera and to provide helpful information on the optimization' of a CCD camera for those who try to develop their own camera. The 2K CCD camera was optimized to have a gain of $1.8e^-/ADU$ and a read out noise of $7e^-$ from an experiment using radioactive $^{55}Fe$ X-ray source. The charge transfer efficiency was measured as 0.9999976 for serial and 0.9999942 for parallel direction, which means $0.5\%$ charge loss along the serial direction and $1.2\%$ along the parallel direction across the chip. The quantum efficiency of the camera was measured from an experiment using a homogeneous light source consisting of a halogen lamp and an integrating sphere with a monochromator. The resulting quantum efficiency of the camera peaked at the wavelength range 600-700 nm with the value of $\~0.89$.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.985-990
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• 2003

In order to demonstrate Advanced Spent Fuel Conditioning Process (ACP), shielding facilities such as hot cell suitable to handling radionuclides and process property will be necessary. But the construction of new facilities needs much money, man-power and time, it is now scheduled to remodel the hot cell, which has already been installed and maintained at Irradiated Material Experiment Facility (IMEF) in the Korea Atomic Energy Research Institute (KAERI). The basic structure and concrete shield wall of hot cell partly have been constructed on the base floor in IMEF building in current status. And hot cell after remodeling will be used for carrying out the lab-scale experiment of ACP. The hot cell was built in accordance with 35 curies of fe-59(1.2 MeV) as design criteria of radiation dose limit. But the radioactive source of ACP is expected to be much higher than design criteria of IMEF, shielding ability of the hot cell in the current status is unsatisfactory to the hot test of ACP. Therefore shield wall shall be reinforced with heavy concrete, steel or lead. In this paper, dose rates are calculated according to ACP source, shielding materials, etc., and reinforcement structures are determined considering the current situation of hot cells, installation of shield windows and the easiness of work.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.63-70
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• 1993

A simplified safety assessment is carried out on rock-cavern type disposal of LLW using the analytical repository source term (REPS) model. For reliable prediction of the leach rates for various radionuclides, degradation of concrete structures, corrosion rate of waste container, degree of corrosion on the container surface, and the characteristics of radionuclides are considered in the REPS model. The results of preliminary assessment show that Cs-137, Ni-63, and Sr-90 are dominant. For the parametric uncertainty and sensitivity analysis, Latin hypercube sampling technique and rank correlation technique are applied. The results of the potential public health impacts show that radiological dose to intruder in the worst case scenario will be negligible and that more attention should be given to near-field performance.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.446-452
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• 2018

To improve the accuracy and safety of irradiation tests in High flux Advanced Neutron Application ReactOr (HANARO), the nuclear energy deposition rate, which is called nuclear heating, was estimated for an irradiation capsule with an iridium sample in the irradiation hole in order. The gamma rays emitted from the radioisotopes (RIs) of the structural materials such as flow tubes of fuel assemblies and heavy water reflector tank were considered as radiation source. Using the ORIGEN2.1 code, emission rates of delayed gamma rays were calculated in consideration of the activation procedure for 8 years and 2 months of HANARO operation. Calculated emission rates were used as a source term of delayed gamma rays in the MCNP6 code. By using the MCNP code, the nuclear heating rates of the irradiation capsules in the inner core, outer core, and heavy water reflector tank were estimated. Calculated nuclear heating in the inner core, outer core, and heavy water reflector tank were 200-260 mW, 80-100 mW, and 10 mW, respectively.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.112-119
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• 2021

Background: This work aims to develop a new imaging system based on a pulse shape discrimination-capable Cs₂LiYCl₆:Ce (CLYC) scintillation detector combined with the rotational modulation collimator (RMC) technique for dual-particle imaging. Materials and Methods: In this study, a CLYC-based RMC system was designed based on Monte Carlo simulations, and a prototype was fabricated. Therein, a rotation control system was developed to rotate the RMC unit precisely, and a graphical user interface-based software was also developed to operate the data acquisition with RMC rotation. The RMC system was developed to allow combining various types of collimator masks and detectors interchangeably, making the imaging system more versatile for various applications and conditions. Results and Discussion: Operational performance of the fabricated system was studied by checking the accuracy and precision of the collimator rotation and obtaining modulation patterns from a gamma-ray source repeatedly. Conclusion: The prototype RMC system showed reliability in its mechanical properties and reproducibility in the acquisition of modulation patterns, and it will be further investigated for its dual-particle imaging capability with various complex radioactive source conditions.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.130-137
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• 2022

In the geological repository of radioactive nuclear waste, anaerobic corrosion can generate hydrogen, and may conservatively lead to the production of hydrogen-air layer. The accumulated hydrogen may cause a hazardous flame propagation resulting from any potential ignition sources. This study numerically investigates the processes of ignition and flame propagation in the layered mixture. Simple geometry was chosen to represent the geological repository, and reactive flow simulations were performed with different ignition power, energy, and locations. The simulation results revealed the effects of power and energy of ignition source, which were also analyzed theoretically. The mechanism of layered flame propagation was suggested, which includes three stages: propagation into the hydrogen area, downward propagation due to the product gas, and horizontal propagation along the top wall. To investigate the effect of the ignition source location, simulations with eight different positions were performed, and the boundary of hazardous ignition area was identified. The simulation results were also explained through scaling analysis. This study evaluates the potential risk of the accumulated hydrogen in geological repository, and illustrates the layered flame propagation in related ignition scenarios.

• Journal of Surface Science and Engineering
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• v.56 no.1
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• pp.84-93
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• 2023

The spent nuclear fuel is burned during the planned cycle in the plant and then generates elements such as actinide series, fission products, and plutonium with a long half-life. An 'interim storage' step is needed to manage the high radioactivity and heat emitted by nuclides until permanent-disposal. In the case of Korea, there is no space to dispose of high-level radioactive waste after use, so there is a need for a period of time using interim storage. Therefore, the intensity of neutrons and gamma-ray must be determined to ensure the integrity of spent nuclear fuel during interim storage. In particular, the most important thing in spent nuclear fuel is burnup evaluation, estimation of the source term of neutrons and gamma-ray is regarded as a reference measurement of the burnup evaluation. In this study, an analysis of spent nuclear fuel was conducted by setting up a virtual fuel burnup case based on CE16×16 fuel to check the total amount and spectrum of neutron, gamma radiation produced. The correlation between BU (burnup), IE (enrichment), and CT (cooling time) will be identified through spent nuclear fuel burnup calculation. In addition, the composition of nuclide inventory, actinide and fission products can be identified.