• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.201-206
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• 2011

A spacer grid assembly is one of the most important structural components of the nuclear fuel assembly of a pressurized water reactor (PWR), and it affects the performance of the fuel assembly. The primary design requirement is that the mechanical integrity of the fuel rod should be maintained by the spacer grid assembly during the operation of the reactor. It was known that fretting damage to the fuel rod can be reduced by adjusting the relative moving displacement between the fuel rod and its support. In this study, we used the finite element method to evaluate the characteristics of a sliding support designed to reduce fretting damage of fuel rods.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.173.1-173.1
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• 2005

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.746-751
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• 2001

Design requirements for the nuclear fuel assembly grid of the pressurized water reactor are reviewed from the mechanical/structural point of view. And mechanical/structural tests and numerical analyses on the various spacer grid candidates that has been uniquely designed by KAERI are carried out to find out their mechanical/structural performance. As a result, the results from the numerical analyses are good agreements with test results.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.297-302
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• 1998

유한요소법을 이용하여 스프링으로 연속 지지되고 축방향 하중이 작용하는 핵연료봉의 자유진동 해석올 수행하였다. 본 해석에는 지지격자 지지점에서 핵연료봉의 변위가 구속되지 않는 실제 경계조건을 반영하였다. 이러한 경계조건은 지지점 스프링 상수에 의하여 핵연료봉 해석모델의 탄성항이 약화되는 현상을 반영할 수 있어서 지지점이 구속된 기존의 모델보다 고유진동수를 작게 예측한다. 스프링 상수가 어떤 임계값 이하를 갖는 경우 고유진동수 뿐만 아니라 모드형상도 크게 변하기 때문에 지지점을 구속한 모델에 의한 해석은 실제 진동현상을 상당히 왜곡 할 수 있다. 핵연료봉에 작용하는 축방향력이 인장력에서 압축력으로 감소함에 따라 고유진동수도 감소하지만 핵연료봉의 고유형상은 변하지 않았다. 지지격자 스프링 상수의 점진적인 감소와 핵연료봉 축방향 압축력의 감소를 동시에 적용하는 경우 고유 진동수는 두 변수를 별도로 적용했을 때 얻은 최소값의 변화에 따르는 경향을 나타내었다.

• Geotechnical Engineering
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• v.13 no.4
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• pp.163-176
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• 1997

It has long been recognized that the H-beam steel rib has many shortcomings when used as a steel support in tunneling. One of the major shortcomings is the shotcrete shadow created behind H-beam flange which eventually reduces the load bearing capacity of shotcrete shell. In many European countries, plate girder as the H-beam steel rib has been replaced by lattice girder which has many advantages over the H-beam steel rib. Successful application of the lattice girder as a steel support requires a thorough investigation on the load bearing capacity of the lattice girder. Therefore, laboratory bending and compression tests were conducted on lattice girders with the aim of investigating the load bearing capacity of the lattice girders. The results of tests show that the load bearing capacity of laIn twice girders is higher than that of H-beams, which indicates that the lattice girder can be effectively used as a support in tunneling.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.897-908
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• 2019

The objective of this study is to evaluate the field support performance of highperformance lattice girder (BK-Lattice Girder) by using numerical analysis. Three types (50, 70, 95-type) of existing and high performance lattice girders were applied to the cross section of highway 2, 3, and 4 lane tunnels to compare the supporting performance. The numerical analysis was the finite element method and the lattice girder was modeled in three dimensions with an elasto-plastic frame. The ground was modeled as a spring receiving only compression. The load was applied as a concentrated load on the central ceiling of the tunnel section. The yield strengths of the lattice girders were determined from the numerical results to compare the supporting performance of lattice girder. In case of 50-type, the yield strengths of high-performance lattice girders were increased by 6.7~10.0% compared with those of the existing lattice girders. In the case of 70-type, the high-performance lattice girders increased yield strengths by 12.1~14.9% than the existing lattice girder. In the case of 95-type, the high-performance lattice girders increased yield strengths by 13.3~20.0% than the existing lattice girder. As a result of numerical analysis, it was considered that the high-performance lattice girder supported better than the existing lattice girder when only the lattice girders were constructed.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.310.2-310.2
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• 2003

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.1
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• pp.51-62
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• 2000

핵연료집합체 검증 프로그램의 일환으로 본 연구에서는 지진과 배과파단이 핵연료집합체의 건선성에 미치는 영향을 검토하였다 원자로 노심의 상세 동적해석을 이용하여 지진 및 배과파단시 핵연료 집합체에 발생하는 전단력 굽힘 모우멘트 및 변위를 계산하였고 또한 집합체를 지지하고 있는 지지격자체의 충격력을 검토하였다 이들 하중에 대한 핵연료집합체의 응력해석을 수행하여 사고조건하에서의 구조적 건전성에 대하여 언급하였고 추후 설계시 고려할 사항을 제시하였다.

• Nuclear Engineering and Technology
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• v.28 no.1
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• pp.17-26
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• 1996

The in-reactor fuel rod support conditions against the fretting wear-induced damage can be evaluated by residual spacer grid spring deflection or rod-to-grid gap. In order to evaluate the impact of fuel design parameters on the fretting wear-induced damage, a simulation methodology of the in-reactor fuel rod supporting conditions as a function of burnup has been developed and implemented in the GRIDFORCE program. The simulation methodology takes into account cladding creep rate, initial spring deflection, initial spring force, and spring force relaxation rate as the key fuel design parameters affecting the in-reactor fuel rod supporting conditions. Based on the parametric studies on these key parameters, it is found that the initial spring deflection, the spring force relaxation rate and cladding creepdown rate are in the order of the impact on the in-reactor fuel rod supporting conditions. Application of this simulation methodology to the fretting wear-induced failure experienced in a commercial plant indicates that this methodology can be utilized as an effective tool in evaluating the capability of newly developed cladding materials and/or new spacer grid designs against the fretting wear-induced damage.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.344.2-344
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• 2001