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Wakai, Takashi; Kobayashi, Sumio; Kato, Shoichi; Ando, Masanori; Takasho, Hideki*
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07
This paper describes a thermal fatigue test on a structural model with a dissimilar welded joint. In the present design of JSFR, there may be dissimilar welded joints between ferritic and austenitic steels especially in IHX and SG. Creep-fatigue is one of the most important failure modes in JSFR components. However, the creep-fatigue damage evaluation method has not been established for dissimilar welded joint. To investigate the evaluation method, structural test will be needed for verification. Therefore, a thermal fatigue test on a thick-wall cylinder with a circumferential dissimilar welded joint between Mod.9Cr-1Mo steel and 304SS was performed. Since the coefficients of thermal expansion of these steels were significantly different, buttering layer of Ni base alloy was installed between them. After the completion of the test, deep cracks were observed at the HAZ in 304SS, as well as at HAZ in Mod.9Cr-1Mo steel. There were many tiny surface cracks in BM of 304SS. According to the fatigue damage evaluation based on the finite element analysis results, the largest fatigue damage was calculated at HAZ in 304SS. Large fatigue damage was also estimated at BM of 304SS. Fatigue cracks were observed at HAZ and BM of 304SS in the test, so that analytical results are in a good agreement with the observations. However, though relatively small fatigue damage was estimated at HAZ in Mod.9Cr-1Mo steel, deep fatigue cracks were observed in the test. To identify the cause of such a discrepancy between the test and calculations, we performed a series of finite element analyses. Some metallurgical investigations were also performed.
Ando, Masanori; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto*; Toyoshi, Akira*; Omae, Takahiro*; Enuma, Yasuhiro*
Nuclear Engineering and Design, 275, p.408 - 421, 2014/08
Times Cited Count：4 Percentile：30.92(Nuclear Science & Technology)To clarify the failure mode of a semispherical tubesheet structure originally designed for SG in the JSFR, a cyclic thermal loading test was performed using a tubesheet model test structure. The tubesheet model made of Mod.9Cr-1Mo steel was subjected to 1,873 cycles of severe thermal transient loads using a large-scale sodium loop, in which sodium heated to 600
C and 250C was flowed repeatedly with periods for each transient of 2 and 1 h, respectively. After the test, the test model was inspected by PT. Then, observation using a SEM and hardness testing were performed. A thermal-hydraulic analysis was also performed to validate the measured temperature history during the thermal transient. Through these examinations and evaluation with thermal-hydraulic analysis, the manner of failure in the tubesheet under cyclic thermal loading is discussed.
Ando, Masanori; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto*; Toyoshi, Akira*; Omae, Takahiro*; Enuma, Yasuhiro*
Nuclear Engineering and Design, 275, p.422 - 432, 2014/08
Times Cited Count：12 Percentile：67.4(Nuclear Science & Technology)In this study, the strength of a tubesheet test model simulating a semispherical tubesheet structure subjected to cyclic thermal transients was evaluated using the finite element analysis (FEA). A test model made of Mod.9Cr-1Mo steel was subjected to 1,873 cycles of severe thermal transient loading using a large-scale sodium loop, in which elevated-temperature sodium at 600C and 250C was flowed repeatedly and kept at the final temperature for 2 and 1 h, respectively. Heat transfer analysis and stress analysis were performed using the sodium temperature data measured during the test. Then, the elastic and inelastic stress analysis results were used to investigate the failure mechanism by creep-fatigue damage and evaluate the failure strength. The evaluation based on the results of inelastic analysis estimated the number of cycles to failure within a factor of 3.
Ando, Masanori; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto*; Toyoshi, Akira*; Omae, Takahiro*; Enuma, Yasuhiro*
Nihon Kikai Gakkai M&M 2013 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.OS1510_1 - OS1510_3, 2013/10
To validate the failure mode and assess creep-fatigue damage evaluation, a thick cylinder test model made of Mod.9Cr-1Mo steel was subjected to 1,873 cycles of accelerated thermal transient loading using a large-scale sodium loop through which liquid sodium at 600C and 250C flowed repeatedly, with the period of each transient being 2 h and 1 h, respectively. After completion of the test, liquid penetrant testing, a surface observation and hardness testing were performed to characterize failure mode. Based on the finite element analysis, creep-fatigue life was evaluated by applying the JSME FRs code. The failure cycles evaluated by rules described in the JSME FRs code was shown to have a safety margin of greater than 300 times for this system.
Wakai, Takashi; Inoue, Osamu*; Ando, Masanori; Kobayashi, Sumio
Transactions of 22nd International Conference on Structural Mechanics in Reactor Technology (SMiRT-22) (CD-ROM), 9 Pages, 2013/08
Ando, Masanori; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto*; Toyoshi, Akira*; Omae, Takahiro*; Enuma, Yasuhiro*
Nuclear Engineering and Design, 255, p.296 - 309, 2013/02
Times Cited Count：19 Percentile：81.37(Nuclear Science & Technology)To verify the failure mode and assess creep-fatigue damage, a thick cylinder test model made of Mod.9Cr-1Mo steel was subjected to 1,873 cycles of accelerated thermal transient loading using a large-scale sodium loop through which liquid sodium at 600 C and 250 C flowed repeatedly, with the period of each transient being 2 h and 1 h, respectively. After completion of the test, the test model was inspected using liquid penetrant testing. Observations using a scanning electron microscope and hardness testing were then performed to characterize creep-fatigue damage in the structural model subjected to cyclic thermal transient loading in a sodium environment. Finite element analysis were performed to evaluate the relationship between creep-fatigue damage and the observed crack conditions.
Kawasaki, Nobuchika; Takasho, Hideki*; Kobayashi, Sumio; Hasebe, Shinichi; Kasahara, Naoto
Proceedings of 2008 ASME Pressure Vessels and Piping Division Conference (PVP 2008) (CD-ROM), 9 Pages, 2008/07
To clarify frequency-dependent attenuation effects of fluid temperature fluctuation on fatigue strength, thermal fatigue strength tests subjected to superposed sinusoidal temperature fluctuations were performed by the SPECTRA test facility. After these fatigue tests, cylindrical test pieces were cut away from the test loop, and cracks were observed on the inner surface of the test pieces. Fatigue lives at crack initiation positions were evaluated based on the test conditions. Adopting power spectrum density functions and frequency transfer functions, fatigue lives were predicted within a factor 3.
Kawasaki, Nobuchika; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto
Proceedings of 2007 ASME Pressure Vessels and Piping Division Conference/8th International Conference on Creep and Fatigue at Elevated Temperatures (PVP 2007/CREEP-8) (CD-ROM), 8 Pages, 2007/07
Thermal fatigue strength tests subjected to sinusoidal fluid temperature waves were performed by the SPECTRA test facility, where frequencies were 0.05, 0.2, and 0.5Hz. Cracks were observed on the inner surface of cylindrical test pieces after testing. 0.05Hz's wave caused a greater number of and deeper cracks than 0.5Hz's wave under the same fluid temperature range and the same fatigue cycles. The crack initiation region of the 0.05Hz's wave was larger than for the 0.5Hz's wave. Estimated fatigue failure cycles based on the frequency transfer functions were compared with test results. Frequency-dependency in failure cycles was observed through these test results, and frequency transfer functions could estimate this dependency. The test results supported the fatigue damage evaluation method with frequency transfer functions.
Kawasaki, Nobuchika; Kubayashi, Sumio; Hasebe, Shinichi; Kasahara, Naoto
Proceedings of 2006 ASME Pressure Vessels and Piping Division Conference (PVP 2006)/International Council on Pressure Vessel Technology (ICPVT-11) (CD-ROM), 8 Pages, 2006/07
The coolant leakage by thermal striping phenomenon should be prevented at nuclear power plants and a lot of efforts are made to develop its evaluation methods. The frequency transfer function method can explain temperature and stress response to fluid temperature history using transfer function models; therefore it is considered as an excellent evaluation method. To measure temperature response of structures to fluid and to confirm their frequency characteristics, transient temperature measurement tests were performed by JAEA. In the transient temperature measurement tests, three different frequencies of sinusoidal fluid temperature waves (0.05, 0.2, 0.5Hz) were controlled using frequency controlled thermal fatigue test equipment (SPECTRA) and temperature responses at inner and outer structural surfaces were measured along the test sections. Frequency effects on temperature attenuation during transfer process from fluid to structures were confirmed and the effective heat transfer function in frequency transfer function method was verified by transient temperature measurement test results.
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.
kasahara, Naoto; Hasebe, Shinichi; Kobayashi, Sumio; Ando, Masanori; Kawasaki, Nobuchika; Morita, Hiroshi*
ASME PVP-Vol.472, P. 2986, 2004/00
Focusing on the cover layer materials (as the Radon Barrier Materials), which could have the effect to restrain the radon from scattering into the air and the effect of the radiation shielding, we produced the radon barrier materials with crude bentonite on an experimental basis, using the rotary type comprehensive unit for grinding and mixing, through which we carried out the evaluation of the characteristics thereof.
Hasebe, Shinichi; Kobayashi, Sumio; Ando, Masanori; Kasahara, Naoto
JNC TN9400 2003-004, 110 Pages, 2003/01
JNC-TN9400-2003-004.pdf:4.23MB
At a nuclear power plant, where fluids of high and low temperatures flow into each other, it is necessary to prevent structural failure damage caused by high cycle thermal fatigue (thermal striping phenomenon). High cycle fatigue test equipment on thermal can be develop 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 crack initiation and their propagation behavior. The test equipment has the following characteristic. (1)Fluid is controlled by a circulation pump, and by continuously changing the flow quantity ratio of high and low temperature Sodium, sinusoidal temperature fluctuations at various period of the test samples can be taken. (2)Mixing is done by the jet flow mix, thus it can generate axisymmetric temperature fluctuations by accelerating the mixing process of high and low temperature Sodium. (3)It can also control the temperature fluctuation, in which short and long term changes are superimposed. (4)Because the test sample cylinder is hollow, analysis of thermal stress and data from crack initiation to crack propagation can easily be obtained. Sinusoidal temperature fluctuations, random temperature fluctuations, and strength testing of the weld zone by test samples made of stainless steel are planned in the next stage.
; Hirakawa, Yasushi; ;
JNC TN9410 2001-023, 84 Pages, 2001/08
JNC-TN9410-2001-023.pdf:6.77MB
NaK (an alloy of sodium and potassium) Flow and Heat Transfer Test Loop was dismantled from January to Februaly 2001. This report shows experience and results obtained in the dismantling. NaK has a low melting point, -12.6C and has high chemical activity even comparing to sodium because of containing potassium of 78wt%. In addition, the dismantling of the NaK loop was the first experience in OEC. Therefore before dismantling NaK loop, evaluation of dismantling method, trainings of NaK handling and experiments of NaK reaction were carried out by all concerned to ensure the safety. As a result, the test loop was safely dismantled and NaK handling method was obtained. Followings are major results of this experience: (1)Fpllowings were confirmed by experiments. (a)When NaK was exposed in atmosphere, NaK super oxide was produced by exothermal reaction with oxygen. However, the effect of thermal diffusion to NaK and a metal tray scarcely leads the ignition. (b)Exposing NaK alternately in low and high oxygen atmosphere increases the possibility of ignition. (c)As nitrogen gas may react exothermally with burning NaK and formulate KNO
, nitrogen gas does not have instant extinguish capability. (2)Cutting NaK pipe in the vinyl-bag filled with argon gas was effective to avoid NaK ignition. (3)Because there were no solidified crevice in components like sodium at the room temperature, NaK equipments were more easily dismantled than sodium equipments.
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JNC TN9450 2001-001, 150 Pages, 2001/06
JNC-TN9450-2001-001.pdf:5.98MB
This report shows the results of crack inspection in crack propagation tests that were carried out at the Air-cooling Thermal Transient Test Facility (ATTF), Test specimens were made of 304 type austenitic stainless steel, and they were the same cylindrical shape, 1,500 mm in height, 130 mm in outer diameter and 30 mm in thickness. And they had initial slits machined on inner surfaces. Firstly the specimens were heated up to 650 C in a furnace, then cooled by pressurized air blowing through the specimen for 90 seconds. These cyclic changes of temperature gradients in the wall of specimens were loaded. Specimens were tested for several years. The specimen No. CPTT-102 with machined two circumferential slits and two semi-elliptical slits was tested up to 10,000 cycles. And the specimen No. CPTT-103 with machined six semi-elliptical slits of different length respectively was tested up to 5,000 cycles. Cracks of specimens were inspected nondestructively fbr a giving cycle in these tests. Applied inspection methods were ultra-sonic testing, potential-drop method and inner surface observation. Ultra-sonic testing was carried out by applying the pulse-echo method. Potential-drop testing was carried out by measurement of localized constant direct current beyond cracks. Photographs of the inner surface of specimens were taken using a bore-scope. The results of ultra-sonic testing have been close to destructive test results. The depth of crack by the potential-drop method was almost corresponding to destructive test results, too. Photographs of the inner surface were synthesized by the computer, and connection between main crack and hair crack was observed.
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JNC TN9450 2000-005, 220 Pages, 2000/06
JNC-TN9450-2000-005.pdf:13.1MB
This report shows the experimental results of crack propagation tests using the air-cooled thermal transient test facility (ATTF). These tests were carried out to get the crack growth data on fundamental structures under cyclic thermal transients. The test specimens were made of 304 type austenitic stainless steel. Geometry is cylindrical shape, 1500 mm in height, 130 mm in outer diameter and 30 mm in thickness. And they had semi-elliptical initial slits machined on inner surfaces. The specimen was heated up to 650 C by furnace, then cooled by pressurized air blowing in the specimen for 90 seconds. Cyclic change of temperature gradients in the wall of specimens was loaded by this sequence. The tests were continued till 10,000 cycles at maximum case. Specimens were tested during several years. The specimen No. CPTT-102 with machined two circumferential slits and two semi-elliptical slits was tested up to 10,000 cycles. And the specimen No. CPTT-103 with machined six semi-elliptical slits of different length respectively was tested up to 5,000 cycles. This report concerns to feature of cracks that grew up from semi-elliptical slits on both No. CPTT-102 and No. CPTT-103.
