• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.60-72
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• 2019

The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1263-1274
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• 2009

Several experimental tests to simulate a reflood phase of a cold-leg LBLOCA of the APR1400 have been performed using the ATLAS facility. This paper describes the related experimental results with respect to the thermal-hydraulic behavior in the core and the system-core interactions during the reflood phase of the cold-leg LBLOCA conditions. The present descriptions will be focused on the LB-CL-09, LB-CL-11, LB-CL-14, and LB-CL-15 tests performed using the ATLAS. The LB-CL-09 is an integral effect test with conservative boundary condition; the LB-CL-11 and -14 are integral effect tests with realistic boundary conditions, and the LB-CL-15 is a separated effect test. The objectives of these tests are to investigate the thermal-hydraulic behavior during an entire reflood phase and to provide reliable experimental data for validating the LBLOCA analysis methodology for the APR1400. The initial and boundary conditions were obtained by applying scaling ratios to the MARS simulation results for the LBLOCA scenario of the APR1400. The ECC water flow rate from the safety injection tanks and the decay heat were simulated from the start of the reflood phase. The simulated core power was controlled to be 1.2 times that of the ANS-73 decay heat curve for LB-CL-09 and 1.02 times that of the ANS-79 decay curve for LB-CL-11, -14, and -15. The simulated ECC water flow rate from the high pressure safety injection pump was 0.32 kg/s. The present experimental data showed that the cladding temperature behavior is closely related to the collapsed water level in the core and the downcomer.

• Progress in Superconductivity
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• v.14 no.2
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• pp.87-91
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• 2012

Metallic magnetic calorimeters (MMCs) are one of the most competitive low temperature detector (LTD) readout sensors. They have the advantages of high time resolution, no heat dissipation, and a wide range of operating temperature. We apply MMCs to our neutrinoless double beta decay ($0v{\beta}{\beta}$) search experiment. A $CaMoO_4$ crystal was employed as both a source of $0v{\beta}{\beta}$ and an energy absorber. The crystal was thermally connected to a MMC sensor. We set a simple thermal model for this detector and measured pulse shapes are compared with a numerical solution of the thermal model.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.88-95
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• 1998

In this paper, we investigated the change of wettability, surface potential decay and dielectric properties caused by ultraviolet-treated, thermal-treated and discharge-treated FRP(fiber reinforced plastics) respectively for finding out the influence of dry treatments effected to electrical characteristics on the surface of polymer composites. For the change of wettability, the contact angle of thermal-treated specimen with the high temperature of $200^{\circ}C$ increased. But that of UV-treated and discharge- treated specimen decreased. The characteristic of surface potential decay shows the tendency of the remarkable decrease on UV-treated and discharge-treated specimens, but no difference on thermal-treated specimen compared with untreated one. Also, for the dielectric properties, it shows the increase at large on the treated specimens and especially, the remarkable increase on thermal-treated one.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2816-2829
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• 2021

Decay heat residuals of spent nuclear fuel (SNF), i.e., the differences between calculations and measurements, were obtained previously for various spent fuel assemblies (SFA) using the Polaris module of the SCALE code system. In this paper, we compare decay heat residuals to their uncertainties, focusing on four PWRs and four BWRs. Uncertainties in nuclear data and model inputs are propagated stochastically through calculations using the SCALE/Sampler super-sequence. Total uncertainties could not explain the residuals of two SFAs measured at GE-Morris. The combined z-scores for all SFAs measured at the Clab facility could explain the resulting deviations. Nuclear-data-related uncertainties contribute more in the high burnup SFAs. Design and operational uncertainties tend to contribute more to the total uncertainties. Assembly burnup is a relevant variable as it correlates significantly with the SNF decay heat. Additionally, burnup uncertainty is a major contributor to decay heat uncertainty, and assumptions relating to these uncertainties are crucial. Propagation of nuclear data and design and operational uncertainties shows that the analyzed assemblies respond similarly with high correlation. The calculated decay heats are highly correlated in the PWRs and BWRs, whereas lower correlations were observed between decay heats of SFAs that differ in their burnups.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2819-2827
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• 2022

The disposal area of a deep geological repository (DGR) for the disposal of spent nuclear fuels (SNFs) is estimated considering the spacing between deposition holes and between disposal tunnels, as determined by a thermal analysis using the decay heat of a reference SNF. Given the relatively large amount of decay heat of the reference SNF, the disposal area of the DGR is found to be overestimated. Therefore, we develop a computer program using MATLAB, termed ACom (Assembly Combination), to combine SNFs when stored in canisters such that the decay heat per canister is evenly distributed. The stability of ACom was checked and the overall distribution of the decay heat per canister was analyzed. Finally, ACom was applied to disposal scenarios suggested in the conceptual design of a DGR for SNFs, and it was confirmed that the decay heat per canister could be evenly distributed and that the maximum decay heat of the canister could be much lower than that of a canister estimated using a reference SNF. ACom can be used to improve the disposal efficiency by reducing the disposal area of a DGR for SNFs by ensuringg a relatively even distribution of decay heat per canister.

• Transactions on Electrical and Electronic Materials
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• v.3 no.4
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• pp.10-15
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• 2002

Surface states of polydimethylsiloxane (PDMS) treated by plasma were investigated by the analysis by x-ray photoelectron spectroscopy (XPS) and surface voltage decay. Plasma treatment causes the silica-like(SiO$\_$x/, x=3∼4) oxidative layer, which is confirmed with XPS, and lowers surface resistivity from 1.78$\times$1014 Ω/square to 1.09$\times$10$\^$13/ Ω/square with increasing the plasma treatment time. By measuring the decay time constant of surface voltage, the calculated surface resistivity was compared with the value directly measured by a voltage-current method, so good agreement between two methods was obtained. It was observed that the plasma treatment led to decrease of the thermal activation energy of the surface conduction from 31.0 kJ/mol of untreated specimen to 21.8 kJ/mol. It is found that our results allow the examination of effects of plasma on electrical properties of PDMS.

• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.57-62
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• 2004

Turbulent drag reduction (DR) efficiency of water soluble poly(ethylene oxide) (PEO) with two different molecular weights was studied as a function of polymer concentration and temperature in a turbulent flow produced via a rotating disk system. Its mechanical degradation behavior as a function of time in a turbulent flow was also analyzed using both a simple exponential decay function and a fractional exponential decay equation. The fractional exponential decay equation was found to fit the experimental data better than the simple exponential decay function. Its thermal degradation further exhibited that the susceptibility of PEO to degradation increases dramatically with increasing temperature.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.75-78
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• 2002

In this paper, we investigated the change of wettability, surface potential decay and surface resistivity caused by thermal-treated and plasma-treated FRP respectively for finding out the influence of electrical characteristics on the surface of polymer composites. For the change of wettability, the contact angle of thermal-treated specimen with the high temperature of 200$^{\circ}C$ increased. But that of plasma-treated specimen decreased. The characteristic of surface potential decay shows the tendency of the remarkable decrease on plasma-treated specimens, but no difference on thermal-treated specimen compared with untreated one. Also, for the surface resistivity, it shows the same trend compared with the change of contact angle. We can conclude that the degradation phenomena of epoxy surface are dominated by the induction of hydrophilicity and hydrophobicity.

• Journal of Photoscience
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• v.9 no.2
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• pp.296-298
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• 2002

Irreversible photobleaching of bacteriorhodopsin (bR), namely denaturation induced by illumination of visible light, was investigated by absorption kinetic measurements. The denaturation kinetics revealed that light illumination significantly enhanced the structural decay of bR. The kinetic analyses showed that the molecular structure of bR denatures according to a single-exponential decay, whereas irreversible photobleaching has two decay components. The decay constant of the slow component of photobleaching is almost same as that in the dark. An Arrhenius plot of the denaturation kinetic constants for the fast and slow components showed similar activation energies of approximately 19 kcal/mol.