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Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Materials Science Forum, 607, p.248 - 250, 2009/00
So far no standard procedure for the positron annihilation lifetime (PAL) technique has been established. A lack of the standards has led to difficulty in ensuring the equivalency and reliability of data from different laboratories. As a first, we conducted an interlaboratory comparison of PAL measurements for metal, polymer and silica glass with agreed procedures for data recording and analysis. The PAL data recorded at different laboratories were analyzed with a single lifetime component for the metal sample and with three components for the others, respectively. Based on the results of the reported positron and ortho-positronium lifetimes, the possible sources of the uncertainties in the PAL measurements are discussed. To reduce the effect of scattered 
rays, a lead shield was placed between the detectors. The uncertainty was significantly decreased, signifying that placing lead shields between the detectors effectively reduced the false signals due to the scattered rays.
Ito, Kenji*; Oka, Toshitaka*; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya; Honda, Yoshihide*; Hosomi, Hiroyuki*; et al.
Journal of Applied Physics, 104(2), p.026102_1 - 026102_3, 2008/07
Times Cited Count：48 Percentile：83.47(Physics, Applied)Interlaboratory comparison of positron annihilation lifetime measurements using synthetic fused silica and polycarbonate was conducted with the participation of 12 laboratories. By regulating procedures for the measurement and data analysis the uncertainties of the positron lifetimes obtained at different laboratories were significantly reduced in comparison with those reported in the past.
Kasahara, Naoto; Iwata, Koji; Imazu, Akira; Horikiri, Morito; Tokura, Sunao*
PNC TN9410 90-032, 321 Pages, 1989/12
Tubesheet structures are one of the most critical portions in the LMFBR components, and also have complicated configurations. Consequently, the specialized evaluation methods are required for design of tubesheets. In the case of structural design of the prototype LMFBR "Monju", the tentative design evaluation method had been suggested. It is the purpose of this study to propose the advanced method, that can be applied to designs of condenced tubesheets and of higher temperature operating ones, which are required in the demonstration LMFBR. As a conventional design method, ASME Sec. III A-8000 is basicaly adopted in the world. A-8000, however, is the elastic design method for LWR where main loading is inner pressure. For a design of tubesheets in LMFBR, It is necessary to make A-8000 adopted to thermal stress and to develop inelastic strain calculation methods. In this study we clarified the application range of A-8000 and proposed the improved method to calculate thermal stresses. The elastic design method based on perforated palate models without A-8000 is also developed. To evaluate inelastic responses of material, the relation between inelastic strain amplifications around holes of tubesheets and ligament efficiencies is obtained in the view point of dependence of inelastic behavior on ligament efficiencies. As the results, we developed the inelastic strain concentration factor which have consistency with the general purpose high temperature design code.
*; ; Iwata, Koji; Imazu, Akira
PNC TN9410 89-105, 201 Pages, 1989/07
This study aims at grasping the thermal transient strength characteristics of typical structures and weldment for FBR plant components, and examining the design evaluation method for creep fatigue failure. Thermal Stress Mitigation Structure Model(1) was subjected to cyclic thermal loading by using Thermal Transient Test Facility for Stuctures(TTS). Heat transfer analyses and elastic thermal stress analyses were carried out using the measured temperature data. Axisymmetric finite element analyses were carried out for most parts, and 3-dimensional calculations was performed for the slitted cylinder. Analyses were performed by using Finite Element Nonliner Structural Analysis System(FINAS). Creep fatigue damage evaluation based on the evaluation method without safety factors ror material strength(TTSDS) was carried out with these analyses results. The relation between creep fatigue damage evaluated by TTSDS and the crack depth of corresponding point was examined. These results correspond with the thermal transient strength tests of other structural elements using TTS so far. These data are to be used for structural thermal transient test data base.
*; *; *; Kasahara, Naoto; *; ; Imazu, Akira
PNC TN9410 89-088, 187 Pages, 1989/06
Thermal transient strength tests of structure models are carried out to develop the design method of the fast breeder reactor components under thermal loadings. The fifth testing model for Thermal Transient, Test Facility for Structures (TTS), "Thermal stress mitigation structure model (2)", have been designed and fabricated. The purpose of this model is to get the thermal transient strength data for the typical shape of FBR components and to confirm the function of specific structures under thermal loading. This testing model is a vertical type cylindrical vessel supported by a skirt. It has seven testing portion for failure test, such as two types of nozzle, a Y-junction, two types of skirt and a plate to shell junction. And it has three testing portion for confirmation of function, such as a thermal insulator, a flow straightener and tube to perforated plate weldments. In designing the model, thermo-hydraulic analysis, heat transfer analysis, thermal Stress analysis were performed. Testing portions were evaluated using the design guide for TTS exclusive use. Material and welding method are basically comparable to the prototype reactor internals.
*; *; *; Imazu, Akira
PNC TN9410 89-100, 56 Pages, 1989/05
A series of biaxial fatigue tests were conducted with 304 steel at 550 
C as the first step of a study on an evaluation of elevated temperature multiaxial creep-fatigue behavior of structural materials. The following results were obtained. (1)A fatigue life under a nonproportional loading decresed to 1/2 - 1/3 compared with a propotional loading. (2)It was shown that an equivalent strain range which is obtained by a strain path integration of mises type equivalent strain is promising to discribe the multiaxial fatigue behavior. (3)It was shown that further investigation should be concentrated on an effect of strain path and strain rate upon the multiaxial fatigue behavior.
; Imazu, Akira
PNC TN9410 89-001, 160 Pages, 1989/01
Many sorts of structural component tests were conducted for the prototype fast breeder reactor "MONJU" with an objective of development of structural design guide for high temperature application, structural integrity assessment method, fabrication-testing guide and in-service inspection guide. This report is composed of many short descriptions of selected structural tests, the test objective, the test method, the test condition and the test result. Structural tests for future large FBRs are also included in this report.
*; ; Imazu, Akira; *
PNC TN9410 88-139, 151 Pages, 1988/08
A simplified thermo-hydraulic-stress analysis code PEGASUS was verified in its applicability to viscous flow examples. The "MONJU" reactor vessel model tested at "Thermal Transient Test Facility for Structures (TTS)" was selected as one of the examples. Other nine examples including basic and practical ones were also analyzed.verification of PEGASUS code was performed comparing the results from PEGASUS code with those from theoretical solutions, experimental data, and the other codes. Results obtained from the comparison are as follows. PEGASUS code gives accurate solutions for laminar viscous flow, and approximate solutions for turbulent viscous flow with adequate value of eddy diffusivity of momentum. In the example of the "MONJU" reactor vessel model the counter flow of hot sodium caused by its buoyancy was found to be analyzed qualitatively. The future problems found in this study are that viscous flow analysis needs much CPU time for the calculation and includes complexity to determine the appropriate fluid properties for turbulent flow.
*; *; Imazu, Akira
PNC TN9410 88-080, 132 Pages, 1988/06
A series of analytical investigations were made into the seismic response characteristics of bellows, as a part of work aiming at establishing reliable seismic design and analysis methodologies for bellows piping systems. Simplified calculation methods were developed for the axial and lateral seismic response of bellows, in which bellows is modeled as an equivalent rod or beam, respectively. Using these methods, spectral response analyses were performed on the bellows with the number of convolutions as a parameter, and the results were compared with detailed FEM analysis by FINAS. Analyses were also made to compare with available vibration test data. The simplified methods were found to give fairly good results when compared with those by FINAS, and relatively conservative results when compared with experimental data. Through this study, simplified methods were established to evaluate the seismic response and stress of bellows with sufficient accuracy for practical design use.
Kasahara, Naoto; Tokura, Sunao*; Iwata, Koji; Horikiri, Morito; Imazu, Akira
PNC TN9410 88-037, 169 Pages, 1988/02
Tubesheet Structures of Heat Exchanger is one of the most important structures in the Fast Breeder Reactor Plants, and simplified analysis methods for design are necessary because of those complex structures. The conventional method exists in ASME Code Sec. III A-8000, which is only available for elastic analysis. In this study we developed simplified inelastic analysis methods on tubesheet structures using the equivalent inelastic properties of perforated region. To define the equivalent elastoplastic stress-strain relation we adopted the Ludwik type equation. And Igari's creep strain equation on perforated plates was examined, which proves to be conservative. As the application of these properties this study proposed two simplified models. The one is equivalent axisymmetric solid plate model to evaluate junction between rim and shroud. The other is partially perforated equivalent solid plate model to evaluate the outermost holes. These models were validated by comparison with thermal transient test data.
; *; *; Imazu, Akira
PNC TN9410 87-181, 447 Pages, 1987/12
This report describes the inelastic analysis and creep-fatigue damage evaluation of a reactor vessel model subjected to severe cyclic thermal transient loadings between 250C and 600C. The object of this study is to present the prospect of damage evaluation method based on inelastic analysis. Many analytical results and evaluated results of the reactor vessel model are presented here, and discussed focusing on the application of inelastic analytical results to the design usage. The results are as follows: (1)Elastically evaluated strain ranges are more than two times larger than inelastically evaluated strain ranges. (2)Creep-fatigue damage directly evaluated from inelastic analysis showed that in some cases there was no safety margin. (3)A new method, including safety margin more than ten against creep-fatigue failure, is presented. (4)By this method, the safety margin could be rationally reduced compared with the current method based on elastic analysis.
Furuhashi, Ichiro*; ; Imazu, Akira
PNC TN9410 87-158, 231 Pages, 1987/11
Simplified analyses of discontinuity thermal stresses were performed using axisymmetrical shell theory for the purpose of saving cost and time of thermal stress calculations in the design of FBR's components. By these analyses, steady and unsteady thermal stresses are to be calculated easily and quickly for the following regions (1)edge of cylinder, (2)discontinuity of material properties and thickness, dissimilar metal pipe joint, (3)axial temperature distribution, cylinder near the liquid surface level, (4)junction of vessel & flange, (5)junction of nozzle and vessel, (6)skirt structures, nozzle safe end, and (7)ring reinforcement. Also, simple formulae were proposed for estimating thermal stresses caused by (9)circumferential temperature distribution of cylinder, (10)thermal striping near the structural wall. By using these results, one can easily evaluate thermal stresses for various shapes and dimensions, and saving of cost and time should be accomplished in the design of FBR's components.
; *; Imazu, Akira
PNC TN9410 87-171, 135 Pages, 1987/10
The objective of this report is to develop non-linear fracture mechanics applicable to the calculation of creep-fatigue crack growth relating to postulated sodium leak. The procedure adopted here is (1) survey and selection of creep-fatigue fracture mechanics parameters, (2) development of analytical method and computer code, (3) analyses of plates with semi-eliptical surface crack, (4) calculation of growth and (5) assessment of crack opening area. CANIS code (Crack ANalysis in Structures) was initially developed for only fatigue crack parameters J and J^ and was extended to creep crack parameters J' and J'^. Fracture mechanics parameters of plate with semi-eliptical surface crack (b/a = 0.167, a/t = 0.25, 0.4, 0.6, 0.8, 0.9) were calculated. Then crack growth under creep-fatigue condition, namely hold time up to 8000 hr. at 500C, was calculated. The crack growth calculation method based on elastic-plastic-creep analysis is described in this report. The preliminary analyses showed that crack opening area seemed to be less than 1 cm
, but additional analytical data and creep crack growth data at lower crack growth rate region were needed for more accurate assessment of crack opening area in the future.
*; *; ; Iwata, Koji; Imazu, Akira
PNC TN9410 87-112, 206 Pages, 1987/09
A series of experimental and analytical investigations was made into the vibration characteristics of bellows, as a part of works aiming at the establishment of seismic design and analysis methods for the piping systems with bellows expansion joints. Vibration tests were made using scaled models of bellows, and eigenvalue analyses were performed using both finite element method (FINAS program) and some simplified methods. Some axial, bending, and shell type modes were identified in the vibration tests in terms of mode shapes and eigenfrequencies. The analysis results by FINAS program were in good accordance with the test results for all the vibration modes, while the simplified formula provided in the EJMA Std. did not give good estimation for bending modes. A new simplified calculation method for bending mode eigenfrequency was developed, in which the fluid-structure interaction effect induced by flowsleeve was also taken into consideration. Through this study, analysis methods to evaluate the vibration characteristics of bellows with simplicity and precision, were established, which will be reflected on the provision of seismic design and anlysis methods for piping systems with bellows expansion joints.
Tsukimori, Kazuyuki*; Iwata, Koji; Imazu, Akira; *; *; Shimakawa, T.*
PNC TN9410 87-126, 93 Pages, 1987/07
There is an idea of the application of piping expansion joints to main piping systems of Large-scale FBRs as one of the cost reduction measures. The internal pressure buckling test of bellows is one of the important items of the FBR piping expansion joints feasibility study. In PNC the internal pressure buckling test is going on in order to establish the analytical method and rules for the internal pressure buckling of bellows. In this report the buckling test results of the series of the sub-scale bellows (12B, 7
30 convolutions) subjected to internal pressure are described, which were obtained during 1986 FY. The followings are the main results. (1)The root bulge occurred in the region between 7 and 10 convolutions and the column squirm occurred in the region between 15 and 30 convolutions. The simple plastic hinge mechanism predicts the critical pressure well in the former region and the simple column squirm analysis in the latter. (2)The initial bending angle of bellows affected the critical pressure badly only in the case of the column squirm. The buckling pressure of bellows must be estimated taking the bending deformation into consideration.
; Furuhashi, Ichiro*; Imazu, Akira
PNC TN9410 87-094, 402 Pages, 1987/06
This report describes flexibility, simplified stress calculation method and simple axisymmetrical modelling method for nozzles which were designed for large EBRs based on the IHX floating support concept. Stress analyses of nozzles were conducted with 3-dimensional solid model etc. under piping reaction force, internal pressure and thermal transient loadings by finite element FINAS code. The results of analyses are as follows; (1)Spring constants representing nozzle flexibility were prepared for piping analyses from the results of 3-dimensional shell analyses, (2)For internal pressure, an equivalent axial force was applicable in piping analyses, (3)Thermal transient loadings of 1 C/sec temperature change caused higher stress than allowable limit, so more discussion is needed in thermal design of the FBRs, (4)Simplified stress calculation methods for each loading were developed, (5)Analytical modelling of 3-dimensional nozzle shapes to axisymmetrical shapes was developed for each loading.
Kasahara, Naoto; Horikiri, Morito; Iwata, Koji; Uno, Tetsuro*; Imazu, Akira; Tokura, Sunao*
PNC TN9410 87-057, 245 Pages, 1987/03
The structural design methods for tubesheets have been studied in connection with the development of fast breeder reactors, because tubesheet structures have complex and 3-dimmensional configulation, and are subjected to severe thermal loading. In Japan the tentative guidelines for structural design methods for tubesheets of FBR plants are proposed by the task group on the design methods of tubesheets in Power Reactor and Nuclear Fuel Development Corporation. The objective of this study is to validate this tentative methods by using data obtained from thermal transient tests of tubesheet models of evaporator and detailed analytical study, and moveover to provide usuful knowledge to rationalize the tentative guidelines. In this report, simplified methods of thermal and stress analyses for tubesheet structures are newly proposed and applied to thermal transient tests of tubesheet models which were carried out in 1984. The works contained in this report are summarized as; (1)Heat transfer analyses with 3-dimensional full model and elastic analyses with the same model are executed on the tubesheet structure, and the mechanism of thermal stress generation in the tubesheets is clarified. (2)Two simplified heat transfer analysis models are developed: the convection film model and the modified perforated plate model. Tbose models are proved to be accurate enough through the comparison with the results of 3-dimensional analyses. (3)Heat-transfer coefficient on the tubesheet structures are discussed with the data of temperature tests and thermal-hydraulicanalyses. As the results, it is shown that the film heat-transfer formula for turbulent flow inside tubes canbe used conservatively for inner surface of shrouds. (4)The simplified inelastic analysis method for tubesheets is developed. This method uses 2-dimensional models considering 3-dimensional effects of shrouds. As the results of comparison with the thermal transient test data of tubesheet model, the ...
; Furuhashi, Ichiro*; Imazu, Akira
PNC TN9410 87-028, 209 Pages, 1987/02
The thermal stresses are generated in the walls of chemical plants, thermal power plants, and fast breeder reactors, etc. during start-up or shut-down of plants or during emergency shut-down. Parametric structural analyses will be required in the structural design of these plants to demonstrate that these thermal stresses are lower than allowable values. This report gives diagrams for calculating thermal stresses due to temperature distribution in wall thickness for various thermal parameters. We can get thermal stresses quickly by these diagrams without parameteric structural analyses. These diagrams can be most effectively applied for choosing the most desirable geometries at the initial stage of the design, even though they are not recommended to be used for the different types of thermal stresses caused by temperature distribution in axial direction of pipings and vessels.
