Thermal transient test and strength evaluation of a tubesheet structure made of Mod.9Cr-1Mo steel, 1; Test model design and experimental results

Ando, Masanori; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto*; Toyoshi, Akira*; Omae, Takahiro*; Enuma, Yasuhiro*

Nuclear Engineering and Design, 275, p.408 - 421, 2014/08

AA2013-0395.pdf:2.65MB

https://doi.org/10.1016/j.nucengdes.2014.04.032

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 600C 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.

Creep-fatigue evaluation of a structural model made of Mod.9Cr-1Mo steel subjected to the cyclic thermal loading

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.

Spectra thermal fatigue tests under frequency controlled fluid temperature variation; Superposed sinusoidal temperature fluctuations tests

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.

Spectra thermal fatigue tests under frequency controlled fluid temperature variation; Strength tests

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.

None

Nakayama, Fusao*; Enokido, Yuji*; Yoshida, Eiichi; Matsumoto, Toshiyuki; Hasebe, Shinichi

JNC TN9420 2005-001, 115 Pages, 2005/03

JNC-TN9420-2005-001.pdf:9.24MB

None

Experimental Study on Properties of High Cycle Thermal Fatigue, 3; Results of sinusoidal temperature fluctuation test at 20 second cycle

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

Spectra thermal fatigue tests under frequency controlled fluid temperature change; Development of test equipment and preliminary tests

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.

Creep properties and microstructure change of FBR grade type 316 stainless steel weld zone

Hasebe, Shinichi; Onizawa, Takashi; Kato, Shoichi

JNC TN9400 2003-019, 62 Pages, 2003/03

JNC-TN9400-2003-019.pdf:3.33MB

We conducted a long-term creep test of weld metal and welded joint made from what we consider optimal filler metals for more than 10000 hours at 550C, in order to evaluate their long-term properties at high temperatures, and select the appropriate filler metals for FBR grade type 316 stainless steel. We also conducted an evaluation of the long-term high temperature strength of the weld metals by observing changes in the microstructures that was subjected to material deterioration. The results obtained are as fo1lows. (1)Weld metal and welded joint made from 316 type and a specific optimal material for 16-8-2 type showed better creep properties than current materials. Especially for 16-8-2 type, the quality improved so much that predominance microstructure stability in the region of long-term. (2)We clearly showed that when -ferrite phase decomposed by long time heating. the Laves phase, phase and austenite phase were precipitated and the remaining -ferrite phase was changed to an -ferrite phase (Cr≒12%, Ni≒2%) as it became a low-alloy and reached equilibrium. (3)The long-term creep strength of the 316 type weld metal tends to decrease as phase separation increases due to a high Cr concentration in -ferrite phase. On the other hand, we confirmed that 16-8-2 type weld metal could maintain long-term creep strength almost as high as the base metal, because there was little separation of inter-metallic compounds due to its low concentration of Cr. (4)We found that change in the microstructure can be easily captured by analyzing the composition of the remaining -ferrite phase. This is an effective method to evaluate long-term high temperature strength.

High-cycle fatigue properties of structural materials for FBR (I); The study on the high-cycles fatigue properties of SUS304 at elevated temperature

Onizawa, Takashi; ; ; Yoshida, Eiichi

JNC TN9400 2002-028, 65 Pages, 2002/03

JNC-TN9400-2002-028.pdf:5.81MB

Fatigue fractures caused by high-cycle fatigue with thermal-striping or flow induced vibration have been occurred recently. For this reason, the importance of high-cycle fatigue life evaluation has been recognized. In this study, the high-cycle fatigue behavior was evaluated based on the results of high-cycle fatigue test up to 10 cycles at elevated temperature on Type 304 stainless steel, and the effect of notch on the high-cycle fatigue lives were investigated, too. The tests were carried out at 500C under a load control mode with frequency set at 30Hz. The results obtained from this study are as follows. (1)The date of high-cycle fatigue properties were obtained in the range below l0 cycles at 500C (2)It is considered that the fatigue limit exists from the examination results in the range up to 10 cycles on smooth fatigue specimen. The internal fatigue fracture wasn't observed in the high-cycle region. (3)The fatigue lives increased with decreasing stress range below 10 cycles on notch specimen. The fatigue lives that calculated from the specimen shape were conservatively evaluated at 10 cycles. (4)Fracture that affect of stationary crack was observed near the crack initiation point on the notch specimen in the high-cycle region.

Experience of NaK flow and heat transfer test loop dismantling

; 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.