• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.347-360
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• 2013

This paper presents an experimental investigation of the small-break loss-of-coolant accident (SBLOCA) and the loss-of-feedwater accident (LOFW) in a scaled integral test facility of REX-10. REX-10 is a small integral-type PWR in which the coolant flow is driven by natural circulation, and the RCS is pressurized by the steam-gas pressurizer. The postulated accidents of REX-10 include the system depressurization initiated by the break of a nitrogen injection line connected to the steam-gas pressurizer and the complete loss of normal feedwater flow by the malfunction of control systems. The integral effect tests on SBLOCA and LOFW are conducted at the REX-10 Test Facility (RTF), a full-height full-pressure facility with reduced power by 1/50. The SBLOCA experiment is initiated by opening a flow passage out of the pressurizer vessel, and the LOFW experiment begins with the termination of the feedwater supply into the helical-coil steam generator. The experimental results reveal that the RTF can assure sufficient cooldown capability with the simulated PRHRS flow during these DBAs. In particular, the RTF exhibits faster pressurization during the LOFW test when employing the steam-gas pressurizer than the steam pressurizer. This experimental study can provide unique data to validate the thermal-hydraulic analysis code for REX-10.

• Korean Journal of Veterinary Research
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• v.23 no.1
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• pp.9-16
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• 1983

The effects of ethanol on Na-K-ATPase activity were investigated with cat kidney homogenate. The results were summarized as follows: 1. Na-K-ATPase activity was inhibited with dose-dependent manner by ethanol of higher concentration than 1%, and showed an estimated $I_{50}$ (the inhibitor concentration to cause 50% inhibition) of 7.5%. 2. Hydrolysis of ATP was linear with the incubation time in the absence and presence of 8% ethanol, whereas it was different with preincubation time in the presence of 15% ethanol. 3. Inhibition of Na-K-ATPase activity by ethanol was not affected by increased enzyme concentration, and showed the reversibility of the inhibitory pattern. 4. Kinetic studies of cationic-substrate activation of Na-K-ATPase showed that ethanol had both properties of classical competitive inhibition for $Mg^{{+}{+}}$ or $K^+ and non-competitive inhibition for ATP or $Na^+$. 5. Arrhenius plot yield two break point at $21^{\circ}$ and $30^{\circ}C$ in the absence of ethanol, whereas showing only one break point at $18^{\circ}C$ in the presence of 8% ethanol. These results suggested that ethanol inhibited Na-K-ATPase activity reversible through a disturbance of microenvironment of lipids associated with the enzyme.

• Nuclear Engineering and Technology
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• v.36 no.5
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• pp.475-484
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• 2004

Extending the lifetime of a nuclear power plant [(hereafter referred to simply as NPP)] is one of the most important concerns in the global nuclear industry. Cables are one of the long-life items that have not been considered for replacement during the design life of a NPP. To extend the cable life beyond the design life, it is first necessary to prove that the design life is too conservative compared with actual aging. Condition monitoring is useful means of evaluating the aging condition of cable. In order to simulate natural aging in a nuclear power plant. a study on accelerated aging must first be conducted. In this paper, evaluations of mechanical aging degradation for a neoprene cable jacket were performed after accelerated aging under tcontinuous and intermittent heating conditions. Contrary to general expectations, intermittent heating to the neoprene cable jacket showed low aging degradation, 50% break-elongation, and 60% indenter modulus, compared with continuous heating. With a plant maintenance period of 1 month after every 12 or 18 months operation, we can easily deduce that the life time of the cable jacket of neoprene can be extended much longer than extimated through the general EQ test. which adopts continuous accelerated aging for determining cable life. Therefore, a systematic approach that considers the actual environment conditions of the nuclear power plant is required for determining cable life.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.979-988
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• 2017

The feasibility of cooling in a pressurized heavy water reactor after a large break loss-of-coolant accident has been analyzed using Multidimensional Analysis of Reactor Safety-KINS Standard code during the recirculation phase. Through evaluation of sensitivity of the fuel channel temperature to various effective recirculation flow areas, it is determined that proper cooling of the fuel channels in the broken loop is feasible if the effective flow area remains above approximately 70% of the nominal flow area. When the flow area is reduced by more than approximately 25% of the nominal value, however, incipience of boiling is expected, after which the thermal integrity of the fuel channel can be threatened. In addition, if a dramatic reduction of the recirculation flow occurs, excursions and frequent fluctuations of temperature in the fuel channels are likely to be unavoidable, and thus damage to the fuel channels would be anticipated. To resolve this, emergency coolant supply through the newly installed external injection path can be used as one alternative means of cooling, enabling fuel channel integrity to be maintained and permanently preventing severe accident conditions. Thus, the external injection flow required to guarantee fuel channel coolability has been estimated.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.2
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• pp.90-96
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• 2021

In this study, the method of determining the state of grid points in the adaptable surface particle method based on grid system developed as a free-surface tracing method was improved. The adaptable surface particle method is a method of determining the state of the grid point according to the shape of the free-surface and obtaining the intersection of the given free-surface and grid line where the state of the grid point changes. It is difficult to determine the state of grid points in the event of rapid flow, such as collision or separation of free-surfaces, and this study suggests a method for determining the state of current grid points using the state of surrounding grid points where the state of grid point are known. A grid layer value was assigned sequentially to a grid away from the free-surface, centering on the boundary cell where the free-surface exists, to identify the connection information that the grid was separated from the free-surface, and to determine the state of the grid point sequentially from a grid away from the free-surface to a grid close to the free-surface. To verify the improved method, a numerical analysis was made on the problem of dam break in which a sudden collision of free-surface occurred and the results were compared, and the results were relatively reasonable.

• Molecules and Cells
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• v.42 no.7
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• pp.546-556
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• 2019

Protein phosphatase 4 (PP4) is a crucial protein complex that plays an important role in DNA damage response (DDR), including DNA repair, cell cycle arrest and apoptosis. Despite the significance of PP4, the mechanism by which PP4 is regulated remains to be elucidated. Here, we identified a novel PP4 inhibitor, protein phosphatase 4 inhibitory protein (PP4IP) and elucidated its cellular functions. PP4IP-knockout cells were generated using the CRISPR/Cas9 system, and the phosphorylation status of PP4 substrates (H2AX, KAP1, and RPA2) was analyzed. Then we investigated that how PP4IP affects the cellular functions of PP4 by immunoprecipitation, immunofluorescence, and DNA double-strand break (DSB) repair assays. PP4IP interacts with PP4 complex, which is affected by DNA damage and cell cycle progression and decreases the dephosphorylational activity of PP4. Both overexpression and depletion of PP4IP impairs DSB repairs and sensitizes cells to genotoxic stress, suggesting timely inhibition of PP4 to be indispensable for cells in responding to DNA damage. Our results identify a novel inhibitor of PP4 that inhibits PP4-mediated cellular functions and establish the physiological importance of this regulation. In addition, PP4IP might be developed as potential therapeutic reagents for targeting tumors particularly with high level of PP4C expression.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.980-992
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• 2024

Steam line break accident (SLB) in the nuclear reactor is one of the representative Non-LOCA accidents in which thermal-hydraulics and neutron kinetics are strongly coupled each other. Thus, the multi-scale and multi-physics approach is applied in this study in order to examine a realistic safety margin. An entire reactor coolant system is modelled by system scale node, whereas sub-channel scale resolution is applied for the region of interest such as the reactor core. Fuel performance code is extended to consider full core pin-wise fuel behaviour. The MARU platform is developed for easy integration of the codes to be coupled. An initial stage of the steam line break accident is simulated on the MARU platform. As cold coolant is injected from the cold leg into the reactor pressure vessel, the power increases due to the moderator feedback. Three-dimensional coolant and fuel behaviour are qualitatively visualized for easy comprehension. Moreover, quantitative investigation is added by focusing on the enhancement of safety margin by means of comparing the minimum departure from nucleate boiling ratio (MDNBR). Three factors contributing to the increase of the MDNBR are proposed: Various geometric parameters, realistic power distribution by neutron kinetics code, Radial coolant mixing including sub-channel physics model.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2099-2112
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• 2024

This study examined the effects of CRUD on reflood heat transfer behaviors of nuclear fuel rods during a loss-of-coolant-accident (LOCA) in a pressurized water reactor using a best-estimate thermal-hydraulic analysis code. Changes in thermal properties and boiling heat transfer characteristics of the CRUD layer were extensively reviewed, and a set of correction factors to reflect the changes was implemented into the code. A heat structure layer reflecting the effects of CRUDs on the properties was added to the outer surface of the fuel cladding. Numerical simulations were conducted to examine the effects of CRUDs on reflood cooling of overheated fuel rods for representative separate and integral effect tests, FLECHT-SEASET and LOFT. In LOFT analysis, the average cladding temperature was increased due to the low thermal conductivity of CRUD during steady-state operation; however, in both analyses, the peak cladding temperature decreased, and the quenching time was reduced. Obtained results revealed that when the porous CRUD layer is deposited on the fuel cladding, two opposite effects appear. Low thermal conductivity of the CRUD layer always increases fuel temperature during normal operation; however, its hydrophilic porous structures may contribute to accelerated reflood cooling of fuel rods during a LOCA.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.165-172
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• 2016

An experimental study of the thermal-hydraulic characteristics of passive safety systems (PSSs) was conducted using a system-integrated modular advanced reactor-integral test loop (SMART-ITL). The present passive safety injection system for the SMART-ITL consists of one train with the core makeup tank (CMT), the safety injection tank, and the automatic depressurization system. The objective of this study is to investigate the injection effect of the PSS on the small-break loss-of-coolant accident (SBLOCA) scenario for a 0.4 inch line break in the safety-injection system (SIS). The steady-state condition was maintained for 746 seconds before the break. When the major parameters of the target value and test results were compared, most of the thermal-hydraulic parameters agreed closely with each other. The water level of the reactor pressure vessel (RPV) was maintained higher than that of the fuel assembly plate during the transient, for the present CMT and safety injection tank (SIT) flow rate conditions. It can be seen that the capability of an emergency core cooling system is sufficient during the transient with SMART passive SISs.

• Journal of Microbiology and Biotechnology
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• v.30 no.3
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• pp.469-475
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• 2020

During meiosis I, programmed DNA double-strand breaks (DSBs) occur to promote chromosome pairing and recombination between homologs. In Saccharomyces cerevisiae, Mec1 and Tel1, the orthologs of human ATR and ATM, respectively, regulate events upstream of the cell cycle checkpoint to initiate DNA repair. Tel1^ATM and Mec1^ATR are required for phosphorylating various meiotic proteins during recombination. This study aimed to investigate the role of Tel1^ATM and Mec1^ATR in meiotic prophase via physical analysis of recombination. Tel1^ATM cooperated with Mec1^ATR to mediate DSB-to-single end invasion transition, but negatively regulated DSB formation. Furthermore, Mec1^ATR was required for the formation of interhomolog joint molecules from early prophase, thus establishing a recombination partner choice. Moreover, Mec1^ATR specifically promoted crossover-fated DSB repair. Together, these results suggest that Tel1^ATM and Mec1^ATR function redundantly or independently in all post-DSB stages.