• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.787-791
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• 2017

Americium-beryllium (Am-Be; n, ${\gamma}$) is a neutron emitting source used in various research fields such as chemistry, physics, geology, archaeology, medicine, and environmental monitoring, as well as in the forensic sciences. It is a mobile source of neutron activity (20 Ci), yielding a small thermal neutron flux that is water moderated. The aim of this study is to develop a model to increase the neutron thermal flux of a source such as Am-Be. This study achieved multiple advantageous results: primarily, it will help us perform neutron activation analysis. Next, it will give us the opportunity to produce radio-elements with short half-lives. Am-Be single and multisource (5 sources) experiments were performed within an irradiation facility with a paraffin moderator. The resulting models mainly increase the thermal neutron flux compared to the traditional method with water moderator.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.183-183
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• 1999

The phases and interface formation of MgF2 on Si(111) were studied by using LEED, AES, and TPD. When thick MgF2 film was deposited on the Si(111) surface at RT뭉 annealed at higher temperatures, a sequence of LEED patterns (no LEED pattern $\longrightarrow$1$\times$1$\longrightarrow$3$\times$1$\longrightarrow$7$\times$7) was observed. On the 1$\times$1 model in which Mg adsorbs on T4 site and F on H3 site could explain the simultaneous desorption of SiF2 and Mg. When thin MgF2 film was deposited, and initial $\alpha$-$\times$1 phase transforms to 3$\times$3 and $\beta$-1$\times$1 by thermal annealing with a slow evaporation of F and diffusion of Mg into the surface. the 3$\times$3 surface changes to ${\gamma}$-1$\times$1 by the selective desorptioon of F under e-beam irradiation and subsesquently to a Mg-induced {{{{ SQRT { 3} }}}} structure by annealing at $600^{\circ}C$.

• Journal of Pharmaceutical Investigation
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• v.4 no.4
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• pp.17-25
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• 1974

1. Neutron acivation analysis of arsenic contained in Korean human liver was studied in the view point of forensic chemistry, using 12 corpses. A sample of 1g was irradiated for 30 mins. in a neutron flux of $1.2{\times}10^{12}n/cm^2/sec$, followed by nitric-sulfuric acid digestion and then by Gutzeit separation. Radio activity was detected by it's scintillation counter. The arsenic content in the liver was found to be $0.01{\mu}g/g$ to $0.15{\mu}g/g$. 2. A rapid and convenient method for the radiochemical determination of minerals by neutron activation analysis was established. After neutron irradiation to the standard soln. of Cu and Mn in pneumatic tube (neutron flux : $1.2{\times}10^{12}n/cm^2/sec$), Cu and Mn were determined by estimating the ratio of the widths under energy peak area in ${\gamma}-ray-spectrogram$. When the standard soln. of Mn and Cu is irradiated for 15 mins. to 18 hrs., recovery test shows that the relative errors are 5.1% and 4.5% for copper and manganese, respectively.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.3-6
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• 1996

The Ultra-high molecular weight polyethylene (UHMWPE) is exclusivity used as the articulation component with metal or ceramic materials in artificial joint prosthesis because of its good mechanical properties. In the long term however, wear of UHMWPE causes complex problems and hence causes loosening of He prosthesis. In this study, we tried to enhance the wear property of UHMWPE by attaching a hydrophilic graft on the UHMWPE surface and by improving surface hardness without deteriorating the mechanical properties of UHMWPE. This was achieved by ion implantation and by ${\gamma}$-irradiation to the surface in acrylic acid solution and by photo-polymerization in divinylbenzen (DVB), diallysophthalate (DAIP) solution. The wear test was performed by a wear testing machine of ball-on-disk type devised by the authors. The UHMWPE with hydrophlic surface and increased surface hardness developed by above treatments showed less volumetric wear.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.711-713
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• 2017

Fiber Brag grating sensors were written in standard Ge-doped telecom optical fiber (Corning SMF-28) using an 800nm femtosecond laser and a phase mask. It were exposed to gamma-radiation up to a dose of 100 kGy to evaluate the radiation effect. The fs-FBG-2 sensor showed incomplete optical characteristics during irradiation, but the fs-FBG-1 sensor showed excellent radiation resistance with Bragg wavelength shift(BWS) of less than 10pm at a dose of 100 kGy.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.789-792
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• 2003

pMOSFET having 10 ${\mu}um$ thickness Gd layer has been tested to be used as a slow neutron sensor. The total thermal neutron cross section for the Gd is 47,000 barns and the cross section value drops rapidly with increasing neutron energy. When slow neutrons are incident to the Gd layer, the conversion electrons are emitted by the neutron absorption process. The conversion electrons generate electron-hole pairs in the $SiO_2$ layer of the pMOSFET. The holes are easily trapped in Oxide and act as positive charge centers in the $SiO_2$ layer. Due to the induced positive charges, the threshold turn-on voltage of the pMOSFET is changed. We have found that the voltage change is proportional to the accumulated slow neutron dose, therefore the pMOSFET having a Gd nuclear reaction layer can be used for a slow neutron dosimeter. The Gd-pMOSFET were tested at HANARO neutron beam port and $^{60}CO$ irradiation facility to investigate slow neutron response and gamma response respectively. Also the pMOSFET without Gd layer were tested at same conditions to compare the characteristics to the Gd-pMOSFET. From the result, we have concluded that the Gd-pMOSFET is very sensitive to the slow neutron and can be used as a slow neutron dosimeter. It can also be used in a mixed radiation field by subtracting the voltage change value of a pMOSFET without Gd from the value of the Gd-pMOSFET.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.793-796
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• 2003

The electronics of a mobile robot ill nuclear facilities is required to satisfied the reliability to sustain survival in its radiation environment. To know how much radiation the robot has been encountered to replace sensitive electronic parts, a dosimeter to measure total accumulated dose is necessary. Among many radiation dosimeters or detectors, semiconductor radiation sensors have advantages in terms of power requirements and their sires over conventional detectors. This paper describes the use of the radiation-induced threshold voltage change of a commercial power pMOSFET as an accumulated radiation dose monitoring mean and that of the photo-current of a commercial PIN Diode as a dose-rate measurement mean. Commercial p-type power MOSFETs and PIN Diodes were tested in a Co-60 gamma irradiation facility to see their capabilities as radiation sensors. We found an inexpensive commercial power pMOSFET that shows good linearity in their threshold voltage shift with radiation dose and a PIN diode that shows good linearity in its photo-current change with dose-rate. According to these findings, a radiation hardened hybrid electronic radiation dosimeter for nuclear robots has been developed for the first time. This small hybrid dosimeter has also an advantage in the point of view of reliability improvement by using a diversity concept.

• Macromolecular Research
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• v.17 no.8
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• pp.580-584
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• 2009

The effects of crystallinity and radiation crosslinking on the physical properties of a microporous high density polyethylene (HDPE) film with Millad3988 as a nucleating agent were investigated. The pores of the HDPE film were affected by the crystallinity. The crystallinity of the HDPE films increased with increasing Millad3988 amount up to 0.1 wt% but decreased with further addition. The mechanical characteristics of the HDPE containing Millad3988 films improved with increasing irradiation dose up to 50 kGy, but decreased at 75 kGy due to severe degradation. The thermal shrinkage behavior of the HDPE films decreased with increasing radiation dose up to 50 kGy. The porosity of the stretched HDPEIMillad3988 films after ${\gamma}$-ray radiation increased with increasing y-ray radiation dose up to 50 kGy. The pores of the irradiated films were formed more easily by a stretching due to the formation of a crosslinked structure.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.167-170
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• 2015

Radioisotope (Nuclear) battery using $^{63}Ni$ was prepared as beta cell. The electroplated $^{63}Ni$ on Ni foil is fabricated, and beta cell and photovoltaic hybrid battery was designed to use at both day and night in space project. A Ni-plating solution is prepared by dissolving metal particles including $^{62}Ni$ and $^{63}Ni$ from neutron irradiation of ($n,{\gamma}$). Electroplating solution of a chloride bath consists on nickel ions in HCl, $H_3BO_3$, and KOH. The deposition was carried out at current density of $10mA\;cm^{-2}$. The prepared beta source was attached on a PN junction and measured I-V properties. The power output at activity of 0.07 mCi and 0.45 mCi were 0.55 pW and 2.69 nW, respectively.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.715-731
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• 2021

Uncertainties are calculated for pressurized water reactor (PWR) spent nuclear fuel (SNF) characteristics. The deterministic code STREAM is currently being used as an SNF analysis tool to obtain isotopic inventory, radioactivity, decay heat, neutron and gamma source strengths. The SNF analysis capability of STREAM was recently validated. However, the uncertainty analysis is yet to be conducted. To estimate the uncertainty due to nuclear data, STREAM is used to perturb nuclear cross section (XS) and resonance integral (RI) libraries produced by NJOY99. The perturbation of XS and RI involves the stochastic sampling of ENDF/B-VII.1 covariance data. To estimate the uncertainty due to modeling parameters (fuel design and irradiation history), surrogate models are built based on polynomial chaos expansion (PCE) and variance-based sensitivity indices (i.e., Sobol' indices) are employed to perform global sensitivity analysis (GSA). The calculation results indicate that uncertainty of SNF due to modeling parameters are also very important and as a result can contribute significantly to the difference of uncertainties due to nuclear data and modeling parameters. In addition, the surrogate model offers a computationally efficient approach with significantly reduced computation time, to accurately evaluate uncertainties of SNF integral characteristics.