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김국철(K.C. Kim),석진익(J.I. Suk) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
A stochastic evaluation of fatigue crack growth in turbine rotor materials is important to enhance the reliability in the integrity analysis of power generation plants. In order to evaluate the scatter of fatigue crack growth length, experimental tests on fatigue crack propagation are carried out at a constant load amplitude using CrMoV turbine rotor steel, and 14 compact tension specimens are tested at the condition of maximum load 10.5 kN, stress ratio 0.1, and 10 ㎐ frequency at room temperature. The crack length is measured at size intervals of 0.2 ㎜ in crack growth, using the compliance method. We observed experimentally that the crack growth rate was strongly dependent upon the previous rate at each cyclic loading. Crack growth length is separated into two parts: previous crack growth rate-dependent length and variation-dependent length. A weight function is introduced for exact analysis. The previous crack growth rate-dependent length is then expressed as a function of two or three terms. The results are compared and evaluated for better prediction.
울진 5, 6호기 원자력 발전소 원자로 소재 조사전 재료 특성
김국철(K. C. Kim),김정태(J. T. Kim),석진익(J. I. Suk),권희경(H. K. Kwon),성운학(U. H. Sung) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
It is necessary to verify the integrity of the reactor vessel in operating the nuclear power plant because the reactor vessel is irradiated continuously by neutrons during the in-service. In order to prevent the brittle fracture due to the irradiation embrittlement, at first, it is confirmed that the reactor vessel would be sufficiently integrated during the design life throughout the preirradiation baseline test. Then, the reactor vessel material is measured for reduction of material properties by the surveillance test in the instrumented irradiation capsule designed for simulating the environment of reactor vessel. For the integrity analysis of the reactor vessel, there are upper-self energy evaluation, pressurized thermal shock (PTS) analysis, and determination of the pressure-temperature limit curve (P-T curve) in accordance with USNRC and ASME criteria. For the PTS and P-T curve, the integrity should be verified against the brittle fracture even in case the reactor vessel has the defect with the size designated at USNRC. Therefore, reactor vessel materiel is required to have excellent fracture toughness. In order to ensure above criteria, the fracture toughness should be evaluated based on reference nil-ductility transition temperature, RT<SUB>NOT</SUB>. The RT<SUB>NOT</SUB> is determined from drop weigh test and impact test, and the reliability of RT<SUB>NOT</SUB> is confirmed from the static and dynamic fracture toughness test. In this study, preirradiation baseline test results were summarized, and investigated on fracture characteristics for Ulchin 5/6 nuclear power plants. This baseline test data will be used as reference data for surveillance.
김국철(K.C. Kim),석진익(J.I. Suk),권희경(H.K. Kwon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.11
A spent nuclear fuel cask should safe in the case of most severe accident loading during transportation. Therefore, in order to verify the integrity of the shipping cask manufactured by doosan heavy industries for the first time in Korea, rapid loading K1C tests has performed as material property evaluation. In this paper, the dynamic fracture toughness obtained by rapid loading K<SUB>IC</SUB> tests is discussed. The procedure of the integrity evaluation of the shipping cask is as follow: First, the maximum flaw size for the full area of forging product of the shipping cask is measured by nondestructive examination. Second, the dynamic fracture toughness test is carried out at -40℃. Third, FEM is performed for the model of the shipping cask with the maximum size flaw measured by NDE under seismic loading. Finally, the integrity of the shipping cask is evaluated by comparing maximum stress intensity factor calculated by FEM with dynamic fracture toughness measured by the experiment. In the integrity evaluation, our company has carried out nondestructive examination and dynamic fracture toughness test, and GNB Company in Germany has carried out FEM analysis. From the evaluation, the integrity of shipping cask was confirmed.