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외면 보수 용접이 원전 고온관 밀림노즐에서의 결함성장에 미치는 영향
나경환,윤은섭,박영섭,Na, Kyung-Hwan,Yun, Eun-Sub,Park, Young-Sheop 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.2
Nickel-based austenitic alloys such as Alloy 82 and 182 had been employed as the weld metals in nuclear power plants (NPPs) due to their high corrosion resistance as well as good mechanical properties. However, since the 2000s, the occurrence of primary water stress corrosion cracking has been reported in conjunction with these alloys in domestic and oversea NPPs. In the present work, we assumed an imaginary crack at the inner surface of a surge nozzle weld that had previously experienced the outside repair welding, and constructed its finite element model. Finite element analysis was performed with respect to the heat transfer, and then to the residual stress for obtaining the total applied stress distributions. These stress distributions were finally converted to the stress intensity factors for estimating crack growth rate. From the comparison of crack growth rate curves for the cases of no repair welding and outside repair welding, it was found that the outside repair welding did not exhibit negative effect on the crack growth for the surge nozzle under consideration in this work; in both cases, the cracks stopped growing before they became the through-wall cracks.
신혜영(Hye-young Shin),나경환(Kyung-hwan Na),박영섭(Young-sheop Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A methodology for hardness measurement on calandria interior surface of CANDU reactors is developed. This is utilized as a tool for an assessment of neutron irradiation embrittlement effect on the calandria. The best representative measurement points and the most applicable hardness test methods are determined in this study, considering not only operating environments such as neutron flux, pressure and temperature but also a continuous operability of the calandria. These results are applicable to a typical CANDU calandria during the period of a replacement of pressure tubes. Though there inevitably remain some permanent marks on the calandria-tubesheet as a result of indentation for hardness measurement, it has not any negative effects on the integrity of the calandria during the continuous operations. This methodology is useful for assuring the suitability of long term operation of CANDU reactors.
윤은섭(Yun Eun Sub),나경환(Na Kyung Hwan),박영섭(Park Young Sheop) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In nuclear power plants, nickel base alloys that have high corrosion resistance and good mechanical properties have been used in tubes, small bore penetrations and dissimilar metal weld materials. But, since 2000, several PWSCC (Primary Water Stress Corrosion Cracking) occurrences have been reported worldwide in various pressure boundary components. PWSCC is the mechanism that forms cracks in susceptible materials in the presence of a corrosion environment and tensile stresses. If the materials and environments are fixed, PWSCC characteristics are mainly determined by tensile stresses. In this paper, PWSCC growth assessment of nickel base alloy dissimilar metal welds are introduced. To calculate the total stress, the operating stress and weld residual stress are considered. The FEA (Finite Element Analysis) method is applied to calculate the weld residual stress, and finally PWSCC growth rate is calculated.