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Hasebe, Shinichi; Kobayashi, Sumio; Tanaka, Hiroshi*; lbaraki, Koichi*; Fukasaku, Hiroshi*
JNC TN9400 2004-034, 73 Pages, 2004/03
JNC-TN9400-2004-034.pdf:6.02MB
In a nuclear power plant, it is necessary to be attentive to fatigue fracture of the structural material caused by cyclic thermal stress due to the mixing of temperature different fluids. The purpose of this study is to obtain data to demonstrate high cycle thermal fatigue evaluation methods by applying the effects of the frequency of temperature fluctuation. A sinusoidal temperature fluctuation test of with a 20 second period was conducted using high cycle fatigue test equipment (SPECTRA). A SUS304 steel pipe was used as the test sample, at an average sodium temperature of 425 deg-C, fluctuation amplitude of 200deg-C and a sodium flow rate of 300 l/min in the test pipe. The results obtained are as follows: (1)valid strength data to verify evaluation methods could be obtained by applying a 20 second cycle temperature fluctuation to the test sample with SPECTRA. A Crack penetrated at about 157,150 cycles. (2)Numerous cracks in an axial direction were observed on the jnner surface of the test sample in the upper flow area. An air fatigue test demonstrated the difference in the strength of the test sample between axial direction and circumferential direction, revealing that cracks were distributed in an axial direction since anisotropic influences easily appear on the hjgh cycle side. (3)An approximated curve obtained by the common relation of crack and axial direction distance indicates that the boundary of a crack would be located about 430 mm downstream from the tapered end of the test sample with the upper now. (4)Crack occurring on the inner surface progressed to a depth of 1 to 2 mm in thecrystal grain, then progressed along the crystal grain boundary. Striations were formed on areas of the fracture surface in the grain, but were not found on the fracture surface of the grain boundary. Sinusoidal temperature fluctuation tests at the periods of 2,5,10,and 40 seconds are planned to confirm the influence of fluctuation frequency responsiveness on structural material
; ; Tanaka, Hiroshi*; lbaraki, Koichi*; Fukasaku, Hiroshi*
JNC TN9400 2004-033, 65 Pages, 2004/02
JNC-TN9400-2004-033.pdf:1.79MB
At a nuclear power plant, where fluids of high and low temperature flow into each other, it is necessary to prevent structural failure damage caused by the high cycle thermal fatigue (thermal striping phenomenon). The Sodium Temperature Controlled Thermal Fatigue Test Equipment (SPECTRA) was developed by modifying the Thermal Transient Test Facility for Structure (TTS) in order to clarify the effect of temperature fluctuation induced by the thermal striping phenomenon on the crack initiation and its propagation behavior. As two electromagnet pumps mix sodium flows both temperature of 600deg-C and 250deg-C, SPECTRA is able to provide the sinusoidal fluctuation of sodium temperature in the specimen which is made as 66.9mm in inner diameter, 11.1mm in thickness and 1600mm in length. The temperature measurement test by stainless steel was carried out using SPECTRA, and the following results were confirmed: (1)Temperature fluctuation periods of 2-20 seconds of sodium can be induced stably for a long term under the conditions of the mean temperature of 425deg-C and the difference of 200deg-C. (2)The sinusoidal temperature fluctuation range is reduced linearly with the axial direction of specimen. (3)Transmission characteristics of the fluctuation amplitude in the specimen's wall are corresponded to known equations for thermal transmission. (4)It can control the temperature fluctuation as superimpose both short and long periods. After this, sinusoidal temperature fluctuation tests for the stainless steel specimen are going to be carried out based on obtained results.