• Nuclear Engineering and Technology
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• v.30 no.1
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• pp.47-57
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• 1998

Boric acid concentrations of the refueling water storage tank and the accumulators for Westinghouse 3-loop type plants are increased to meet the post loss of coolant accident shutdown requirement for the extended fuel cycles from 12 months to 18 months. To maintain long term cooling capability following a LOCA, the switchover time is examined using BORON code to prevent the boron precipitation in the reactor core with the increased boron concentrations. The analysis results show that hot leg recirculation switchover times are shortened to 7.5 hours from 24 hours after the initiation of LOCA for Kori 3&4 and 8 hours from 18 hours for Ulchin 1&2, respectively. The How path in the mode J for Kori 3&4 is recommended to realign to the simultaneous recirculation of both hot and cold legs from the cold leg recirculation, as done by Ulchin 1&2.

• Analytical Science and Technology
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• v.22 no.4
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• pp.302-306
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• 2009

A trace amount of boron in steel significantly influences its mechanical and physical properties. A prompt gamma ray activation analysis (PGAA) method is used to measure boron in low alloy steel samples of KRISS 101-01-C21~C26. NIST SRMs of 362, 364, 1761 and 1767 serve as the control standards to validate the measurement method. The measured values of the NIST SRMs are consistent with their certified values within the expected uncertainties, except for that of NIST SRM 362. Experimental uncertainties are evaluated according to the guidelines given by the International Organization for Standardization (ISO). The expanded uncertainties are calculated with a coverage factor of 2, at approximately 95% confidence level. The calculated relative expanded uncertainties of boron mass fractions are between 3% and 7% at the mg/kg level. The results are compared with the results measured by the solvent extraction-inductively coupled optical emission spectrometry (ICP/OES) method.

• Polymer(Korea)
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• v.36 no.5
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• pp.549-554
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• 2012

It was known that triphenyl phosphate wasn't homogeneously dispersed in HDPE/EPDM/boron carbide blends, which caused the decrease in mechanical properties. HDPE, EPDM, boron carbide, and triphenyl phosphate were blended with PE-g-MAH(polyethylene-graft-maleic anhydride) as a compatiblizer for improving the miscibility of triphenyl phosphate. Tensile strength of HDPE/EPDM/boron carbide blends decreased with increasing the contents of triphenyl phosphate for flammability. However, the mechanical properties of HDPE/EPDM/boron carbide/triphenyl phosphate blends increased by the addition of compatiblizer because triphenyl phosphate was homogeneously mixed in the blend system. The homogeneous dispersibility of triphenyl phosphate was confirmed by using scanning electron microscopy (SEM). Increased thermal stability and flammability derived from high miscibility of triphenyl phosphate were confirmed by the results of thermogravimetric analysis (TGA) and limiting oxygen index (LOI). A self-extinguishing HDPE/EPDM/boron carbide/triphenyl phosphate blend was successfully fabricated with more than 21% LOI.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1464-1470
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• 2022

This paper presents a high performance burnable absorber named as CIMBA (Cylindrically Inserted and Mechanically Separated Burnable Absorber) for the soluble-boron-free SMR. The CIMBA is the cylindrical gadolinia inserted into the annular fuel pellets. Although the CIMBA utilizes the spatial self-shielding effect of the fuel material, a large reactivity upswing occurs when the gadolinia is depleted. To minimize the reactivity swing of the CIMBA-loaded FA, two approaches were investigated. One is controlling the spatial self-shielding effect of the CIMBA as burnup proceeds by a multi-layered structure of the CIMBA (ML-CIMBA) and the other is the mixed-loading of two different types of CIMBA (MIX-CIMBA). Both approaches show promising performances to minimize the reactivity swing, where the MIX-CIMBA is more preferable due to its simpler fabrication process. In conclusion, the MIX-CIMBA is expected to accelerate the commercialization of the CIMBA and can be used to achieve an optimal soluble-boron-free SMR core design.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.534-538
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• 1991

A procedure for spectrophotometric determination of traces of boron in high-purity trichlorosilane (TCS) is proposed utilizing an adsorptive separation. NaCl is chosen as an Lewis base adsorbent which forms a complex with boron compounds in TCS, and is well dissolved in sulfuric acid-quinalizarin color-forming agent without causing an interference in colorimetric measurements. The proposed adsorptive separation method is free from the formation of silica gel and gas bubbles during the analysis of TCS. The method reveals that the boron concentration in a semiconductor grade TCS is 6.1 ${\mu}$g/l within the standard deviation of ${\pm}$20%. On the other hand, the boron concentration of the purified TCS which is separated from NaCl-boron compounds complex is reduced to 0.2 ${\mu}$g/l, showing the efficient applicability of NaCl to the adsorptive separation. The effectiveness of NaCl for the removal of boron in TCS purification is also described in comparison with other well-known adsorbents.

• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.648-653
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• 2018

Elimination of soluble boron from reactor design eliminates boron-induced reactivity accidents and leads to a more negative moderator temperature coefficient. However, a large negative moderator temperature coefficient can lead to large reactivity feedback that could allow the reactor to return to power when it cools down from hot full power to cold zero power. In soluble boron-free small modular reactor (SMR) design, only control rods are available to control such rapid core transient. The purpose of this study is to investigate whether an SMR would have enough control rod worth to compensate for large reactivity feedback. The investigation begins with classification of reactivity and completes an analysis of the reactivity balance in each reactor state for the SMR model. The control rod worth requirement obtained from the reactivity balance is a minimum control rod worth to maintain the reactor critical during the whole cycle. The minimum available rod worth must be larger than the control rod worth requirement to manipulate the reactor safely in each reactor state. It is found that the SMR does have enough control rod worth available during rapid transient to maintain the SMR at subcritical below k-effectives of 0.99 for both hot zero power and cold zero power.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.305-309
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• 2014

When sunlight irradiates a boron-doped p-type solar cell, the formation of BsO2i decreases the power-conversion efficiency in a phenomenon named light-induced degradation (LID). In this study, we used boron-doped p-type Cz-Si solar cells to monitor this degradation process in relation to irradiation wavelength, intensity and duration of the light source, and investigated the reliability of the LID effects, as well. When halogen light irradiated a substrate, the LID rate increased more rapidly than for irradiation with xenon light. For different intensities of halogen light (e.g., 1 SUN and 0.1 SUN), a lower-limit value of LID showed a similar trend in each case; however, the rate reached at the intensity of 0.1 SUN was three times slower than that at 1 SUN. Open-circuit voltage increased with increasing duration of irradiation because the defect-formation rate of LID was slow. Therefore, we suppose that sufficient time is needed to increase LID defects. After a recovery process to restore the initial value, the lower-limit open-circuit voltage exhibited during the re-degradation process showed a trend similar to that in the first degradation process. We suggest that the proportion of the LID in boron-doped p-type Cz-Si solar cells has high correlation with the normalized defect concentrations (NDC) of BsO2i. This can be calculated using the extracted minority-carrier diffusion-length with internal quantum efficiency (IQE) analysis.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.487-494
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• 2020

Polyurethane/modified boron nitride (PU/m-BN) composite was synthesized from the poly(tetra methylene glycol) (PTMG), 4,4'-methylenebis(phenyl isocyanate) (MDI), and modified boron nitride (m-BN). The modification of boron nitride and synthesis of PU/m-BN composite were confirmed by Fourier transform infrared (FT-IR) spectroscopic analyses. The mechanical properties of the PU/m-BN composites were measured using the universal testing machine (UTM) and the thermal properties of the composites were investigated ser flash analysis (LFA) and UL94 measurements. As a result, the thermal conductivity of the polyurethane composite increased to 1.19 W/m·K, and the flame retardancy of the easy to burn polyurethane, which was not self-extinguishing was improved to UL94 V-1 grade.

• Analytical Science and Technology
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• v.5 no.1
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• pp.127-134
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• 1992

Effects of boron addition on microstructure and phases of plasma are melted tungsten have been investigated by optical microscopy, scanning electron microscopy, Auger electron spectroscopy, X-ray diffractometer, measurements of grain size and hardness. The change in the microstructure upon boron addition was studied by optical microscopy. It was observed that the grain refinement was induced upon content within the limit of solubility. When the boron content was above the solubility limit, two phases of primary tungsten and eutectic structure were observed and confirmed by AES and XRD analysis. It was also shown that recrystallization temperature was increased and recrystallized grain size was reduced as boron content increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.383-391
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• 2011

The hot-stamping technique is used to manufacture high-strength parts by press forming by heating at a temperature above the Austenite transformation temperature and then rapid cooling. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to show the microstructures and to investigate the mechanical properties under different heat-treatment conditions. The heat treatment of water quenching was conducted at the various temperatures and different elapsed times. These can be practical data useful when boron steels are used for hot stamping. Furthermore, the microstructures and mechanical properties of the spot-welded specimen with coatings and counterpart materials (SPRC 340, SPRC 590) is investigated in order to determine the welding characteristics of boron steel at different welding condition.