• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.380-387
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• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.282-293
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• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• Journal of Radiation Protection and Research
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• v.47 no.3
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• pp.152-157
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• 2022

Background: The hemi-body electron beam irradiation (HBIe^-) technique has been proposed for the treatment of mycosis fungoides. It spares healthy skin using an electron shield. However, shielding electrons is complicated owing to electron scattering effects. In this study, we developed a thimble-like head bolus shield that surrounds the patient's entire head to prevent irradiation of the head during HBIe^-. Materials and Methods: The feasibility of a thimble-like head bolus shield was evaluated using a simplified Geant4 Monte Carlo (MC) simulation. Subsequently, the head bolus was manufactured using a three-dimensional (3D) printed mold and Ecoflex 00-30 silicone. The fabricated head bolus was experimentally validated by measuring the dose to the Rando phantom using a metal-oxide-semiconductor field-effect transistor (MOSFET) detector with clinical configuration of HBIe^-. Results and Discussion: The thimble-like head bolus reduced the electron fluence by 2% compared with that without a shield in the MC simulations. In addition, an improvement in fluence degradation outside the head shield was observed. In the experimental validation using the inhouse-developed bolus shield, this head bolus reduced the electron dose to approximately 2.5% of the prescribed dose. Conclusion: A thimble-like head bolus shield for the HBIe^- technique was developed and validated in this study. This bolus effectively spares healthy skin without underdosage in the region of the target skin in HBIe^-.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2078-2084
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• 2020

Magnesium oxide (MgO) and Zinc oxide (ZnO) nanoparticles (NPs) have been successfully synthesized by solid-solid reaction method. The structural properties of ZnO and MgO NPs were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results indicated a formation of pure MgO and ZnO NPs. The mean diameter values of the agglomerated particles were around to be 70 and 50 nm for MgO and ZnO NPs, respectively using SEM analysis. Further, a wide-range of nuclear radiation shielding investigation for gamma-ray and fast neutrons have been studied for Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. FLUKA and Microshield codes have been employed for the determination of mass attenuation coefficients (μ_m) and transmission factors (TF) of Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. The calculated values for mass attenuation coefficients (μ_m) were utilized to determine other vital shielding properties against gamma-ray radiation. Moreover, the results showed that Zinc oxide (ZnO) nanoparticles with the lowest diameter value as 50 nm had a satisfactory capacity in nuclear radiation shielding.

• The Journal of Korean Society for Radiation Therapy
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• v.12 no.1
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• pp.85-90
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• 2000

• 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 Korean Society of Radiology
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• v.9 no.7
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• pp.459-465
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• 2015

Energy absorption distribution according to lead shielding for 511 keV ${\gamma}$ ray was evaluated using a Monte Carlo simulation in PET/CT. Experimental method was performed about the depth of skin surface(0.07), lens(3) and the depth(10) was conducted by using ICRU Slab phantom. Difference of energy absorption distribution according to lead thickness and effect of air gap according to distance of lead and phantom. As a result, study showed that using a lead shielding makes high energy distribution by backscatter electron. As a distance between lead and phantom increased, energy absorption distribution gradually decreased. 9 cm or more air gap should exist to prevent effect of backscatter electron which reaches skin surface, when 0.25 mmPb shielding is used. Also 1 cm or more air gap was needed to prevent the effect in 0.5 mmPb. If air gap was not concerned, 0.75 mm or more lead thickness was necessary to prevent effect of backscatter electron.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.2025-2037
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• 2021

The influence of lead cations on natural quartz (QZ) from Egypt as a glass shielding material for the composition with nominal formula (10Na₂O - (90 - x) QZ - xPbO (where x = 30, 35, 40, 45 and 50 mol %)) was examined. The studied samples are synthesized via the melt quenching method at 1050 ℃. The X-ray diffraction XRD patterns were confirmed the glass nature for studied samples. Moreover, the optical properties, and the transparency for all compositions were examined by UV-Vis spectroscopy. Also, the major elemental composition of the natural quartz were estimated via the X-ray fluorescence (XRF) technique. Further, the density and molar volume were determined. Furthermore, the nuclear shielding parameters such as, mass attenuation coefficient, effective atomic number, electronic density, the total atomic, and electronic cross sections as well as the mean free path, and the half value layer with different gamma ray energies (81 keV-1407 keV) were calculated. Besides, the results showed that the shielding behavior towards the gamma ray radiation for all glass samples was increased as the increment in PbO concentration in the glass system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.95-101
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• 2017

In this paper, the sizing removal condition for the pretreatment of composite materials is obtained numerically by applying an image processing algorithm and nickel-plated carbon fiber is fabricated by a dry process method to enhance its electromagnetic shielding performance. Sizings that are wrapped in a polymer type material during the manufacturing of carbon fiber should be removed for dry coating. A numerical value, that is the correlation, can be obtained by determining the regular pattern of the carbon fiber in the image taken by a scanning electron microscope (SEM) after the sizing is removed. The application of the proposed numerical method to the SEM image of the fiber after the sizing is removed with solution, compressed air, solution and compressed air (hybrid), showed that this method of eliminating the sizing is superior to the hybrid method. Then, by spreading the carbon fiber roll with the sizing removed, we were able to produce nickel plated carbon fiber by the roll-to-roll sputtering method. The electromagnetic shielding performance of the fabricated 30, 40 and 100 nickel coated carbon fibers was measured. The Korea Advanced Institute of Science and Technology evaluated the electromagnetic shielding performance of the 100 nickel-coated carbon fiber to have a maximum value of 73.2 (dB) and a minimum value of 66.7 (dB). This is similar to the electromagnetic shielding rate of copper and shows that this material can be used as a cable for EV / HEV automobiles.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.613-618
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• 2014

In this study, nitrogen doped graphene oxide (GO) was prepared using liquid phase ammonia treatment to improve its electrical properties. Also, the aminated GO was manufactured into a film format and the electromagnetic interference (EMI) shielding efficiency was measured to evaluate its electrical properties. The XPS result showed that the increase of liquid phase ammonia treatment concentration led to the increased nitrogen functional group on the GO surface. The measurement of EMI shielding efficiency reveals that EMI shielding efficiency of the liquid phase ammonia treated GO was better than that of non-treated GO. When GO was treated using the ammonia solution of 21% concentration, the EMI shielding efficiency increased by -5 dB at higher than 2950 MHz. These results were maybe due to the fact that nitrogen functional groups on GO help to improve the absorbance of electromagnetic waves via facile electron transfer.