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; Aoto, Kazumi; Onizawa, Takashi;
JNC TN9400 2001-042, 35 Pages, 2001/03
A study about non-destructive technique in Type 304 stainless steel, which is a main structural material in Fast Breeder Reactor plant, is being performed. In this study, the magnetic field change is considered as the non-destructive technique. This technique has a possibility that the damage before crack initiation is detected. We report that the results about the magnetic field change during creep damage known as time-dependent damage, in order to examine the applicability of non-destructive technique based on magnetic field change. The results are as follows. (1)The magnetic field changes during creep compared the magnetic field of creep-damaged specimen with that of only aged specimen. We have observed the area, which the magnetic field changes steeply as creep, (2)The fracture occurred in the area, which the magnetic field changes steeply. This result indicates that the fracture position is estimated by the magnetic field change. Based on these results, it is considered that creep damage is detected by magnetic field change.
Huang, J.
JNC TN9400 2001-046, 84 Pages, 2001/02
JNC-TN9400-2001-046.pdf:2.01MB
Electron impact ionization is a common way used in high temperature mass spectrometry to obtain ion source for vaporization analysis. For most of the atomic vapor species, their electron impact ionization cross sections are experimentally measured and can be found in database. For various molecular vapor species, however, both theoretic estimation and experimentally measured data are very limited. The cross sections of sodium-containing molecules are the most important parameters to calculate their partial vapor pressures. Up to date, neither experiment data nor theoretic result can be found in literatures. So a theoretic estimation has to be made for further vapor pressure measurements. In this study, the cross sections of sodium-containing molecules have been evaluated systematically in quantum mechanical level for the first time. The main possible sodium-containing vapor species in Fe-Na-O-H system, i.e. NaO(g), NaOH(g), Na
O(g) and Na(g) are taken into account. It is found that the classic model such as additive rule as well as its modified version (MAR) are not suitable for calculation of ionization cross sections when electron impact energy is low. A recent Binary-Encounter-Bethe(BEB) model using molecular orbital parameters is employed to calculate the cross sections of sodium molecules. The results are demonstrated as a function of impact electron energy. Reliability of the data predicted by BEB model is investigated. These data are very valuable for future study on vaporization behaviors of sodium complex compounds by high temperature mass spectrometry.
; Yoshida, Eiichi; Aoto, Kazumi
JNC TN9400 2001-025, 53 Pages, 2001/01
JNC-TN9400-2001-025.pdf:6.49MB
In this report the effects of sodium environment on the low-cycle fatigue and creep-fatigue behavior of Mod.9Cr-1Mo steel, which is a promising material for steam generator of future large scale FBR, was evaluated. The main results obtained were as follows; (1)The low-cycle fatigue lives in sodium were longer than those in air, which is the same as results on 2-1/4Cr-1Mo steel and no strength reduction effect could be detected. It was considered that the increase of fatigue life in sodium was mainly based on the extension of crack initiation life caused by restrained oxidation of specimen surface. (2)The creep-fatigue life of tensile hold tests in sodium was within the scatter of that in air under the same conditions. It is because creep damage in the bulk of the specimen was dominant in both environments due to the limited oxidation in sodium and the arrest of surface cracks in air. On the other hand, the creep-fatigue life of compressive hold tests in sodium tended to be closer to the average fatigue life in air. It is because oxidation in sodium was negligible and creep damage during a compressive hold time was small. (3)The fatigue and creep-fatigue life in sodium calculated using usual rule showed good agreement with experimental results.
; Aoto, Kazumi
JNC TN9400 2000-103, 32 Pages, 2000/09
JNC-TN9400-2000-103.pdf:1.94MB
In this study, the change of lath structure with the increase of distance from fractured surface was observed in detail and the localization of creep damage to decide fracture position was investigated. As the results of the relationship between lath width and distance from fractured surface, the lath width obviously increased as a distance from fractured surface decreased. Lath widths in the different positions of as-received specimen were almost same. These result indicates that recovery of lath structure lacalizes with creep damage. It was considered that the coarsening of precipitates caused localization of recovery in lath structure. Area fraction of precipitates and cross-section of each precipitate in different positions from fractured surface were measured and compared. There were no differences in area fraction of precipitates and cross-section of each precipitate in different positions. Therefore it was found out that the reason for localization of recovery of lath structure was not coarsening of precipitates.
Ueno, Fumiyoshi; Otori, Norikazu
JNC TN9400 2000-097, 55 Pages, 2000/09
JNC-TN9400-2000-097.pdf:1.19MB
If high temperature sodium is burned in humid air, its compound will become high temperature melt of sodium hydroxide as a solvent. If this melt includes peroxide ion, it will be a considerably active aggressive and corrosive for steels. This study was carried out in order to investigate the ability of presence of peroxide ion in sodium hydroxide solvent at high temperature. Laser Raman Spectroscopy was employed to analyze the Raman spectra of sodium peroxide and mixed specimen of sodium hydroxide with sodium peroxide. These reagents were heated up to 1073K under Ar gas atmosphere in the specially made vesse1. Detectability and stability of peroxide ion at high temperature were investigated. Also we investigated about superoxide ion by using sodium peroxide and potassium superoxide. Superoxide ion was induded in sodium peroxide as an impurity. As the result, the stability of peroxide ion in high temperature melt was showed up to 873K for sodium peroxide and 823K for sodium hydroxide mixed with sodium peroxide. And as the results for superoxide ion, its stability was showed as up to 873K for unmixed potassium superoxide and up to 773K for sodium hydroxide mixed one. Additionally, it was considered that superoxide ion will not change into peroxide ion in sodium hydroxide solvent at high temperature.
Huang, J.; Furukawa, Tomohiro
JNC TN9400 2000-101, 47 Pages, 2000/08
JNC-TN9400-2000-101.pdf:1.52MB
A vapor pressure measurement instrument was set up by utilizing the "Microvision Plus (LM70)" quadrupole mass spectrometer combined with the Knudsen vapor effusion cell. The purpose of the vapor pressure measurement is to obtain reliable thermodynamic data of sodium-iron complex compounds. Then, the behaviors of these compounds in various environmental conditions can be investigated in detail for analysis of sodium-leak related accidents in fast breeder reactors (FBR). Therefore, the reliability of the measurement system is of great importance. The following major procedures were made step by step. (1)Vertical alignment arrangements (2)Alignment of the ion mass in Q-mass analyzer (3)"True" signal identification (4)Noise reducing (5)Determination of electron impact conditions (6)Sensitivity improvement by adjusting parameters (7)Temperature calibration (8)Vapor pressure calibration First, special attention was paid to the mechanical settlements, exploration of the parameters' effects, calibration of temperature and pressure. Second, the vapor pressure measurement system was optimized for the specific requirements based on the extensive investigation in this study. Furthermore, it is confirmed that the measured pressures of the standard vapor species (silver and lead) are accurate. Finally, identical result can be reproduced in the same conditions so that the measurement system is believed to be reliable for the future researches.
Wakai, Takashi; Aoto, Kazumi
JNC TN9400 2001-078, 115 Pages, 2000/06
JNC-TN9400-2001-078.pdf:2.39MB
Structure Safety Engineering Group of JNC/OEC makes efforts to develop the guideline for the defect assessment procedures for large scale fast breeder reactor (FBR) components based on the fracture mechanics. The guideline will be applied to the leak before break (LBB) assessment of the piping system of FBR with flaws. A creep-fatigue crack growth assessment procedure as the principal content of the guideline is proposed based on the linear damage summation concept in this report. For some typical flaw model, fracture mechanics parameters and material strength properties are also appended to the report.
; *; ; ; Aoto, Kazumi;
JNC TN9400 2000-059, 43 Pages, 2000/05
JNC-TN9400-2000-059.pdf:2.08MB
The purpose of this study is to understand the material properties of manufacturable high-purity iron and high-purity iron-based alloy in present technology and to get an applicable prospect for the structural and functional material of the frontier fast reactor. Then the about 10kg high-purity iron and iron-based alloy were melted using a cold-crucible induction melting furnace under the ultra-high vacuum. Subsequent to that, the compatibility between the melted material and the high-temperature sodium environment which is a special feature of the fast reactor and tensile property at room and elevated temperatures were investigated using the melted materials. Also, the creep test using the high-purity 50%Cr-Fe alloy at 550
C in air in order to understand the high temperature creep property. ln addition, the material properties such as thermal expansion coefficient, specific heat and electrical resistance were measured and to evaluate the outlook for the structural material for the fast reactor. The following results were obtained based on the property test and evaluation. (1)lt was possible to melt the about 10kg high-purity ingot and high-purity 50%Cr-Fe alloy ingot using a cold-crucible induction melting furnace under the ultra-high vacuum. (2)The tensile tests of the high-purity 50%Cr-Fe alloy were performed at room and elevated temperatures in order to understand the deformation behavior. From the experimental results, it was clear that the high-purity 50%Cr-Fe alloy possesses high strength and good ductility at elevated temperatures. (3)The physical properties (the thermal expansion coefficient and specific heat etc.) were measured using the high-purity 50%Cr-Fe alloy. lt was clear that the thermal expansion coefficient of high-purity 50%Cr-Fe alloy was smaller than that of SUS304. (4)From the corrosion test in liquid sodium, the ordinary-purity iron showed the weight loss after corrosion test. However the high-purity iron showed ...
Momma, Yoshio*; *; ; ; ; Aoto, Kazumi
JNC TN9400 2000-044, 22 Pages, 2000/03
JNC-TN9400-2000-044.pdf:1.37MB
ln the past the microstructural observation was mostly applied to understand the materials behavior qualitatively in R&D of the new materials and the life prediction for the fast breeder reactor components. However, the correlation between the changes in properties and microstrutures must be clarified to ensure the structural integrity. Particularly we are interested in the method to correlate the long-term properties and microstructural changes at high temperatures. The current research is to quantify the changes in microstructure of the weld metal for the welded structure of the reactor vessel. ln this research we have conducted creep testing of the weld metals at 823 and 873K up to 37,000h. Two types of the weld metals (16Cr-8Ni-2Mo and 18Cr-12Ni-Mo) were subjected to the creep testing. Based on the areas of the precipitates, the microstructural characterization with time and creep damage was attempted. The creep strength of the 16Cr-8Ni-2Mo weld metal is lower than that of the 18Cr-12Ni-Mo one at higher stresses, shorter times. But there is a trend toward to become similar strength with lower stresses and increasing times. The creep-rupture ductility of the 16Cr-8Ni-2Mo weld metal is superior to that of the 18Cr-12Ni-Mo one. The creep-rupture takes place at the interface of the sigma (
) phases precipitated in the delta (
) ferrites at 823K lower stresses and 873K. The amount of precipitates in the 16Cr-8Ni-2Mo weld metal is smaller than that in the 18Cr-12Ni-Mo one at each temperature and stress. Also it is apparent that the amount of the precipitates is primarily responsible to the decomposition of the phase, because the amount of the residual ferrites measured by the Magne-Gauge reduces with times. Using the Larson-Miller parameter it was possible to correlate the amount of the precipitates linearly with the LMP values.
; Yoshida, Eiichi; Aoto, Kazumi
JNC TN9400 2000-042, 112 Pages, 2000/03
JNC-TN9400-2000-042.pdf:8.55MB
A sodium-water reaction drove from the single tube break in steam generator of FBR might overheat labor tubes rapidly under internal pressure loadings. lf the temperature of tube wall becomes too high, it has to be evaluated that the stress of tube does not exceed the material strength limit to prevent the propagation of tube rupture. This study clarified the tensile and creep properties of Mod.9Cr-1Mo steel at ultra-high temperature which will be used in evaluation of the tube burst by sodium-water reaction. The strain rates for tensile test are from 10%/min to 10%/sec, and creep-rupture time is maximum 277sec. The range of test temperature is 700C to 1300C. The main results obtained were as follows; (1)The evaluation data on the relationship between tensile strength and strain rate and creep-rupture strength in shorter time on Mod.9Cr-1Mo steel were acquired. (2)Short-term mechanical properties of Mod.9Cr-1Mo steel were evaluated based on the results of tensile and creep-rupture tests up to 1300C. As a result of the evaluation, recommended equation of creep-rupture strength in the short-term was proposed. (3)Tensile and creep-rupture strength of Mod.9Cr-1Mo steel tube showed the value which was higher than the 2 1/4Cr-1Mo steel, and it was proven to have the superior properties.