• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.10a
• /
• pp.177-183
• /
• 1997

The fuel rod for PWR is supported by the spring of the sapcer grid to maintain its axial location and lateral space between fuel rods to get proper functions during the residence in the reactor. The long exposure duration makes the spring to be relax and loss the spring force that results in a fuel rod rattling which may cause fuel rod failure. Here considering the spring behaviour as a function of burnup the reaction forces of the springs are calculated by the finite element program developed herein to evaluate the integrity of the fuel rod from fretting. The results are compared with previous data and ANSYS for the validation of the program and procedures.

• Nuclear Engineering and Technology
• /
• v.53 no.9
• /
• pp.2990-3002
• /
• 2021

The mechanical interaction between the fuel pellet and the cladding tube of a nuclear fuel rod is a very important for safety studies as this phenomenon could lead to fuel failure and release of radioactivity. To investigate the ductility of cladding tubes used in WWER type nuclear power plants, several mandrel tests were performed in the Centre for Energy Research (EK). This modified mandrel test was used to model the mechanical interaction between the fuel pellet and the cladding using a segmented tool. The tests were conducted at room temperature and at 300 ℃ with inactive as-received and hydrogenated cladding ring samples. The results show a gradual decrease in ductility as the hydrogen content increases, the ductile-brittle transition was seen above 1500 ppm hydrogen absorbed.

• Nuclear Engineering and Technology
• /
• v.43 no.5
• /
• pp.405-412
• /
• 2011

Used nuclear fuel will likely be stored dry for extended periods of time in the USA. Until a final disposition pathway is chosen, the storage periods will almost definitely be longer than were originally intended. The ability of the important-tosafety structures, systems, and components (SSCs) to continue to meet storage and transport safety functions over extended times must be determined. It must be assured that there is no significant degradation of the fuel or dry cask storage systems. Also, it is projected that the maximum discharge burnups of the used nuclear fuel will increase. Thus, it is necessary to obtain data on high burnup fuel to demonstrate that the used nuclear fuel remains intact after extended storage. An evaluation was performed to determine the conditions that may lead to failure of dry storage SSCs. This paper documents the initial technical gap analysis performed to identify data and modeling needs to develop the desired technical bases to ensure the safety functions of dry stored fuel.

• Journal of the Korean Society of Industry Convergence
• /
• v.24 no.3
• /
• pp.315-321
• /
• 2021

In this study, the natural frequency analysis of the fuel pipe and vibration test jig was performed as a basic study to determine the vibration characteristics of the vehicle's fuel pipe and the stability analysis of fatigue failure of the pipe. The natural frequencies of the fuel pipe and the fuel pipe with the test jig were calculated and the results were compared. As a result of the analysis, it was found that the natural frequency of the fuel pipe and the natural frequency of the test jig differed about 7 times, so that the vibration of the test jig did not affect the vibration of the fuel pipe. In addition, as a result of the natural frequency analysis of the fuel pipe itself and the pipe with the test jig attached, the maximum error is less than about 1%. In the future, it was suggested that the analysis of the design changed fuel pipe may be performed without a test jig.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.3
• /
• pp.26-31
• /
• 2014

High temperature fuel cell system, such as molten carbonate fuel cells(MCFC) and solid oxide fuel cells(SOFC), are capable of operating at MW rated power output. The power output change of high temperature fuel cell imposes the thermal and mechanical stresses on the fuel cell stack. To minimize the thermal-mechanical stresses on the stack and increase the systems reliability, we should divide the power plant configuration to several banks. However, the improvement of reliability in fuel cell power plant system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we evaluate the cost for operation and installation, the benefit for electric energy and thermal energy sales, and the system reliability for several cases : these cases relate with the bank configuration.

• Nuclear Engineering and Technology
• /
• v.33 no.1
• /
• pp.73-82
• /
• 2001

Pressurized water reactor(PWR) fuel rods. which are continuously supported by a spring system called a spacer grid(SG), are exposed to reactor coolant at a flow velocity of up to 6-8 m/s. It is known that the vibration of 3 fuel rod is generated by the coolant flow, a so-called flow-induced-vibration(FIV), and the relative motion induced by the FIV between the fuel rod and the SG can wear away the surface of the fuel rod, which occasionally leads to its fretting failure. It is, therefore, important to understand the vibration characteristics of the fuel rod and reflect that in its design. In this paper, vibration analyses of the fuel rod with two different SGs were performed using both analytical and experimental methods. Updating of the finite element(FE) model using the measured data was performed in order to enhance confidence in the FE model of fuel rods supported by an SG. It was found that the modal parameters are very sensitive to the spring constant of the SG.

• Journal of Applied Reliability
• /
• v.15 no.4
• /
• pp.241-247
• /
• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.04a
• /
• pp.203-206
• /
• 2005

The objective of study on composite cylinder for alternative fuel vehicle is to develop safe, efficient, and commercially viable, on-board fuel storage system for the fuel cell vehicle or natural gas vehicle that use highly compressed gaseous fuel such as hydrogen or natural gas. This study presents the whole procedure of development and certification of a type 3 composite cylinder of 207bar service pressure and 70 liter water capacity, which includes design/analysis, processing of filament winding, and validation through various testing and evaluation. Design methods of liner configuration and winding patterns are presented. Three dimensional, nonlinear finite element analysis techniques are used to predict burst pressure and failure mode. Design and analysis techniques are verified through burst and cycling tests. The full qualification test methods and results for validation and certification are presented.

• Nuclear Engineering and Technology
• /
• v.52 no.10
• /
• pp.2402-2409
• /
• 2020

Analytical criteria for the onset of fuel fragmentation and Burst Fission Gas Release in fuel rods with ballooned claddings are formulated. On that basis, the GRSW-A model integrated with a fuel behaviour code is updated. After modification, the updated code is successfully applied to simulation of the Halden LOCA test IFA-650.12. Specifically, the calculation with Burst Fission Gas Release during the test resulted in prediction of cladding failure, whereas it could not be predicted at the test planning, before new models were implemented. A good agreement of the current model with experimental data for transient Fission Gas Release in the tests IFA-650.12 and IFA-650.14 is shown, as well.

• Nuclear Engineering and Technology
• /
• v.43 no.6
• /
• pp.509-522
• /
• 2011

FRAPCON-3.4a and FRAPTRAN 1.4 are the most recent versions of the U.S. Nuclear Regulatory Commission (NRC) steady-state and transient fuel performance codes, respectively. These codes have been assessed against separate effects data and integral assessment data and have been determined to provide a best estimate calculation of fuel performance. Recent updates included in FRAPCON-3.4a include updated material properties models, models for new fuel and cladding types, cladding finite element analysis capability, and capability to perform uncertainty analyses and calculate upper tolerance limits for important outputs. Recent updates included in FRAPTRAN 1.4 include: material properties models that are consistent with FRAPCON-3.4a, cladding failure models that are applicable for loss-of coolant-accident and reactivity initiated accident modeling, and updated heat transfer models. This paper briefly describes these code updates and data assessments, highlighting the particularly important improvements and data assessments. This paper also discusses areas of improvements that will be addressed in upcoming code versions.