• Nuclear Engineering and Technology
• /
• v.56 no.3
• /
• pp.907-915
• /
• 2024

Various core designs with multi-batch fuel management (FM) are proposed and optimized for an innovative small modular reactor (iSMR), focusing on enhancing the inherent safety and neutronic performance. To achieve soluble-boron-free (SBF) operation, cylindrical centrally-shielded burnable absorbers (CSBAs) are utilized, reducing the burnup reactivity swing in both two- and three-batch FMs. All 69 fuel assemblies (FAs) are loaded with 2-cylindrical CSBA. Furthermore, the neutron economy is improved by deploying a truly-optimized PWR (TOP) lattice with a smaller fuel radius, optimized for neutron moderation under the SBF condition. The fuel shuffling and CSBA loading patterns are proposed for both 2- and 3-batch FM with the aim to lower the core leakage and achieve favorable power profiles. Numerical results show that both FM configurations achieve a small reactivity swing of about 1000 pcm and the power distributions are within the design criteria. The average discharge burnup in the two-batch core is comparable to three-batch commercial PWR like APR-1400. The proposed checker-board CR pattern with extended fingers effectively assures cold shutdown in the two-batch FM scenario, while in the three-batch FM, three N-1 scenarios are failed. The whole evaluation process is conducted using Monte Carlo Serpent 2 code in conjunction with ENDF/B-VII.1 nuclear library.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.412-414
• /
• 2009

In recent times, starting up polymer electrolyte membrane fuel cells(PEMFC) in sub-zero condition is a great challenge of fuel cell electric vehicle(FCEV). The water produced in a cathode during PEMFCs operate. The water changes into the form of solid/ice in sub-zero temperatures and this makes trouble in PEMFC cells. Voltage of PEMFC drops and cold startup is failed. This paper describes an experimental study on the effect of thermal cycle to degradation of MEA in PEMFC.

• Nuclear Engineering and Technology
• /
• v.52 no.12
• /
• pp.2887-2900
• /
• 2020

Cladding failure in a fuel rod during operation in a BWR is analyzed using a FALCON code-based model. Comparative calculation with a neighbouring, intact rod is presented, as well. A considerable 'hot spot' effect in cladding temperature is predicted with the SLICE-DO model due to a thermal barrier caused by the localized crud deposition. Particularly significant overheating is expected to occur on the affected side of the cladding of the failed rod, in agreement with signs of significant localized crud deposition as revealed by Post Irradiation Examination. Different possibilities (criteria) are checked, and Pellet-Cladding Mechanical Interaction (PCMI) is shown to be one of the plausible potential threats. It is shown that PCMI could lead to discernible concentrated inelastic deformation in the overheated part of the cladding. None of the specific mechanisms considered can be experimentally or analytically identified as an only cause of the rod failure. However, according to the current calculation, a possibility of cladding failure by PCMI cannot be excluded if the crud thickness exceeded 300 ㎛.

• Nuclear Engineering and Technology
• /
• v.56 no.4
• /
• pp.1407-1424
• /
• 2024

In Pressurized Water Reactors, most of the failed fuel rods are often observed at the periphery of the fuel assembly, especially near the core baffle. The rod vibration-induced fretting wear is a significant failure mechanism strongly correlated with the coolant and support conditions. This paper presents a coupled vibration model of double-rod to predict the grid-to-rod fretting (GTRF) wear. A motion-dependent fluid force model is used to simulate the coolant cross flow, the gap constraints with asymmetric stiffness between spring and dimple on the vibration form, and the fretting wear are discussed. The results show the effect of the coupled vibration on the deterioration of wear, providing a sound theoretical explanation of some failure phenomena observed in the previous experiment. Exploratively, we analyze the impact of the baffle jet on the GTRF wear, which indicates that the high-velocity cross-flow will significantly affect the vibration forms while sharply changing the wear behavior.

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.3
• /
• pp.224-231
• /
• 2009

The improvement of cold start capability is one of the most challenging tasks to be solved for commercialization of fuel cell vehicle. In this study, cold start test and ice blocking test(IBT) of fuel cell stack were carried out under various operating conditions. This fuel cell stack can be thawed from -20$^{\circ}$C within 25s and the voltage change was found to be comprised of 4 steps; the first step is the voltage decrease by overpotential, the second step is the voltage increase by the cell temperature increase, the third step is the voltage decrease by ice blocking, and the last step is the voltage increase by thawing. Bootstrap startup was failed after shutdown at temperature under 40$^{\circ}$C because of much condensed water in the fuel cell. Quantitative estimation of cold start capability have been demonstrated by ice blocking test(IBT). In the results, it was found that cold start capability was improved double every 10$^{\circ}$C from 30$^{\circ}$C to 65$^{\circ}$C and enhanced by 30% at the condition of SR 3/4 compared to SR 1.5/2.0 and enhanced by 20% with dry purge condition compared to with RH 50% purge condition.

• Elastomers and Composites
• /
• v.49 no.4
• /
• pp.305-312
• /
• 2014

Most of military supersonic aircraft use an afterburner. It plays an important role in performing unusual duties for supersonic flight, takeoff, and combat situations. Recently, repetitive fuel leakage from the inner piston packing rubber of afterburner fuel pump in an aircraft J85-GE-21 turbojet engine has happened. These failures have only happened in one manufacturer's parts of two manufacturers. Thus, the cause of these failures was investigated through the comparative analysis for both the failed and the unfailed with two different manufacturers using various analysis methods. The failure analysis was performed using analysis methods such as swelling or swelling ratio, total sulfur content, polymer identification, loading and surface area of carbon black, and hardness. Consequently, the main cause of this failure was identified to be insufficient loading of carbon black as a reinforcing agent, together with small surface area of carbon black and somewhat low sulfur content.

• Journal of KSNVE
• /
• v.11 no.3
• /
• pp.401-409
• /
• 2001

Passive type mufflers installed on every car haute inherent problem of lowering engine power and fuel efficiency caused by backpressure which is byproduct of complex internal structure. Recent improvements like installing a calve to change exhaust gas path depending on power requirement and rpm have only marginally improved performance. Tremendous amount of recent research works on active exhaust noise control have failed to commercialize because of numerous physical and economical reasons. In this paper, a unique seal-active muffler using difference of transmission paths is presented. In this system exhaust pipe is divided into two and joined again downstream. Exhaust noise is reduced by destructive interference when two-divided noise join again with transmission paths'difference which is half of the wavelength of a main noise frequency. One divided path has a sliding mechanism to change length thereby transmission path length difference is adjusted to entwine rpm change. The proposed system has minimal backpressure and does not need a secondary sound source like a speaker so it can overcome many problems of failed active noise control methods. We have verified proposed system's superior performance by simulation and comparison experiment with passive mufflers.

• Korean System Dynamics Review
• /
• v.7 no.2
• /
• pp.35-56
• /
• 2006

Korea is implementing strong regulatory derives such as Feed in Tariff to provide incentives for renewable energy developers. But if the government is planning to increase the renewable capacity with only "Price policy" not considering the investors behavior in the competitive electricity market, the policy would be failed. It is necessary system thinking and simulation model analysis to decide government's incentive goal. This study is focusing on the assesment of the competitiveness of renewable energy with the current Feed in Tariff incentives compared to the traditional energy source, specially coal and gas. The simulation results show that the market penetration of renewable energy with the current Feed-in-Tariff level is about 60-70% of the government goal under condition that the solar energy and fuel cell are assumed to provide the whole capacity set in the governmental goal. If the contribution from solar and fuel cell is lower than planned, the total penetration of renewable energy will be dropped more. Notably, Wind power turned out to be proved only 10% of government goal because of its low availability.

• Nuclear Engineering and Technology
• /
• v.41 no.2
• /
• pp.179-186
• /
• 2009

This paper presents a thermal creep test under internal pressure and post-test characterization performed on high burnup (68 MWd/kgU) ZIRLO. This research has been done by the CSN, ENRESA, and ENUSA in order to investigate the behavior of advanced cladding materials in contemporary PWRs at higher burnup under dry cask storage conditions. Also, to investigate the hydride reorientation, the cool-down of the samples after the test has been done in a coordinated manner with the internal pressure. The creep results obtained are consistent with the expected behavior from reference CWSR material, Zr-4. During the test, the material retained significant ductility: one specimen leaked during the test at an engineering strain of the tube section of 17%; remarkably, the crack closed due to de-pressurization. Although significant hydride reorientation occurred during the cool-down under pressure, no specimen failed during the cool-down.

• Plant Journal
• /
• v.6 no.3
• /
• pp.46-52
• /
• 2010

This study investigated the coating failure of the blades of booster fans for the 200 MW flue gas desulfurization plant. Although the arc sprayed SM8222 have been tried as blade coating materials aimed to apply as alternatives of Metcoloy(R)2 due to better corrosion-erosion resistance but it is failed. Bond strength tests and practical field experiences have demonstrated high velocity oxy-fuel(HVOF) coating method with Diamalloy 3004 as an alternative to Metcoloy(R) 2 arc spray.