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JAEA Reports

The strain criterion of the liner material of the secondary coolant system of Monju

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JNC TN9400 2001-029, 40 Pages, 2001/01

JNC-TN9400-2001-029.pdf:0.93MB

Based on the lower limit of high temperature tensile and bending test results of SM400B, a criterion of strain for the Monju liner was proposed: Membrane and bending strain : $$varepsilon$$ m + $$varepsilon$$ b $$varepsilon$$ m+ $$varepsilon$$b $$leqq$$ 15% RT$$<$$T$$<$$350$$^{circ}$$C $$varepsilon$$ m+ $$varepsilon$$b $$leqq$$ 30% 350$$^{circ}$$C$$leqq$$T$$leqq$$1000$$^{circ}$$C This criterion must be applied with considering the following reference value for membrane strain, in order to prevent instable fracture arising from necking. This reference value was determined based on uniform elongation obtained by high temperature tensile tests. Membrane strain : $$varepsilon$$ m $$varepsilon$$ m $$leqq$$ 5% RT$$<$$T$$<$$350$$^{circ}$$C $$varepsilon$$ m $$leqq$$ 10% 350$$^{circ}$$C$$leqq$$T$$leqq$$1000$$^{circ}$$C The liner is subject to multiaxial stress state under temperature history due to heating by contacting to high temperature sodium and subsequent cooling. It was shown that the above strain criterion was valid under such circumstances, including other factors that could affect material properties.

JAEA Reports

Extension of finite element nonlinear structural analysis system 'FINAS'; Modeling of thinning process of structures in temperature analysis

Tsukimori, Kazuyuki; Furuhashi, Ichiro*

JNC TN9400 2001-015, 80 Pages, 2000/11

JNC-TN9400-2001-015.pdf:2.62MB

It is important to consider the thinning process in analyzing the behavior of structures including the change of their strength when thinning of structures is significant due to corrosion etc. The thinning process has already been considered in the integrity analyses of the liner affected corrosion thinning due to leaked sodium. However, in these cases the thinning process was considered only in stress analyses not in both temperature analyses and stress analyses, since the thickness of the liner was thin. In the cases of thick structures or the structures of which temperature gradient in the thickness is expected to be large due to thermal boundary conditions, the thinning process should be considered in the temperature analyses as well as stress analyses. In this study the function of modeling of thinning process in temperature analysis was developed. The concept of the method, the formulation, installation to 'FINAS', guideline of usage and the verification of the function are described. A simplified model of corrosion problem of a tube is pick up as an example. The effecct of thinning process in temperature analysis is discussed.

JAEA Reports

Interpretation of FAENA and TIFFSS experiment; Comparison of fatigue strength evaluation methods on thermal striping

kasahara, Naoto; Lejeail, V.*

JNC TN9400 2001-013, 46 Pages, 2000/09

JNC-TN9400-2001-013.pdf:0.97MB

Since thermal striping is a coupled thermohydraulic and thermomechanical phenomenon, sodium mock-up tests were usually required to confirm structural integrity. CEA and JNC have developed evaluation procedures of thermal striping to establish design-by-analysis methodology for this phenomenon. In order to compare and to validate these methods, two benchmark problems were planned under EJCC contract. One of benchmarks provided by CEA is temperature and fatigue evaluation of tubes and plates tests performed with the EAENA facility. Another problem from JNC is the same evaluation of plates tests conducted by the TIFFSS facility. This report describes the results of intercomparison of fatigue strength evaluation methods through application to both FAENA and TIFFFSS expeliments.

JAEA Reports

Relaxation function method for evaluation of general thermal loads

kasahara, Naoto

JNC TN9400 2001-012, 31 Pages, 2000/08

JNC-TN9400-2001-012.pdf:1.06MB

A rational analysis method for general thermal transient problems was proposed, by utilizing tansient response characteristics of structures. Structures can not respond to quick change of fluid temperature, since they have finite time constants. Low rate changes of fluid temperature hardly induce thermal stresses because of temperature homogenization in structures. In order to quantify above transient characteristics, author developed a relaxation function method that describes Green function of structures. This function can be applied to sensitivity analysis of thermal stress to fluid temperature and to optimization of heat removal systems.

JAEA Reports

Inelastic structural design approach using their relaxation locus

kasahara, Naoto

JNC TN9400 2001-007, 43 Pages, 2000/08

JNC-TN9400-2001-007.pdf:0.81MB

Elevated temperature structural design codes pay attention to strain concentration at structural discontinuities due to creep and plasticity, since it causes to enlarge creep-fatigue damage of materials. One of the difficulties to predict strain concentration is its dependency on loading, constitutive equations, and relaxation time. This study investigated fundamental mechanism of strain concentration and its main factors. The results revealed that strain concentration was caused from strain redistribution between elastic and inelastic regions, which can be quantified by the characteristics of structural compliance. Characteristic of compliancc is controlled by elastic region in structures and is insensitive to constitutive equations. It means that inelastic analysis is easily applied to get compliance characteristics. By utilizing this fact, simplified inelastic analysis method was proposed based on charactelistics of compliance change for prediction of strain concentration.

JAEA Reports

"Local solid element modeling" for detailed analyses of floor liner

Tsukimori, Kazuyuki

JNC TN9400 2000-086, 103 Pages, 2000/08

JNC-TN9400-2000-086.pdf:3.67MB

ln order to evaluate the integrity of the floor liner of "MONJU" at sodium leakage accident, nonlinear finite element analyses have been conducted considering the effect of thinning of the liner due to molten salt type corrosion. Modeling by shell elements is appropriate since liner is composed of thin plates, however, it is difficult to deal with the very local strain behaviors. 0n the other hand, modeling by solid elements makes the numerical calculation impractical. If we extract the small part of the liner which includes local discontinuities, it is possible to evaluate local strain behaviors practically by using the solid element analysis model of the part. To realize this approach, the method to generate all the boundary displacements of the part model from the shell element analysis result of total structure is needed. The aims of this study are to develop the method to deal with the incompatibility between shell and solid elements at part model boundary, and to build numerical analysis circumstances including this method to make the detailed nonlinear finite element analyses of the floor liner of "MONJU" possible. Summary of the results is shown below, (1)The problem of the incompatibility between shell and solid elements was solved by introducing weighting function at 'T' and 'L' type corners and the interpolation function of 4-node rectangular plate bending element at the connection between liner plate and frame. (2)Software system was developed by using 'FINAS' and verified. (3)This approach was applied to one of the cases of the floor liner analyses of "MONJU" at sodium leakage accident. The analysis result showed that three-dimensional local strain behavior could be evaluated directly. ln addition, it was confirmed that the result by shell element analysis was conservative in evaluation of strain compared with that by solid element analysis in this case.

JAEA Reports

Interpretation of FAENA and TIFFSS experiment; Comparison of temperature evaluation methods on thermal striping

kasahara, Naoto; Lejeail, V.*

JNC TN9400 2001-014, 44 Pages, 2000/06

JNC-TN9400-2001-014.pdf:1.2MB

Since thermal striping is a coupled thermohydraulic and thermomechanical phenomenon, sodium mock-up tests were usually required to confirm structural integrity. CEA and JNC have developed evaluation procedures of thermal striping to establish design-by-analysis methodology for this phenomenon. In order to compare and to validate these methods, two benchmark problems were planned under EJCC contract. One of benchmarks provided by CEA is temperature and fatigue evaluation of tubes and plates tests performed with the FAENA facility. Another problem from JNC is the same evaluation of plates tests conducted by the TIFFSS facility. This report describes the results of intercomparison of temperature evaluation methods through application to both FAENA and TIFFFSS experiments.

JAEA Reports

Investigation of technologies on structure and materials that contribute to the reduction of construction cost and elongation of design life of FBRs

JNC TN9400 2001-021, 290 Pages, 2000/05

JNC-TN9400-2001-021.pdf:8.1MB

For the commercialization of FBRs, not only construction cost but also maintenance cost must be reduced. At the same time, design life should be extended. For this purpose, elevated temperature design standard has been successively updated and new materials have been developed. However, more efforts are necessary to make FBR competitive against advanced LWRS. From this viewpoint, this report widely surveyed innovative technologies that had not been assessed in the current effort for the improvement of the design standard but were considered to be able to contribute to cost reduction. Areas investigated were specification and fabrication of structural material, design evaluation, fabrication, inspection, operation and maintenance. Promising technologies were selected from the result and the extent of improvement of the design of the intermediate heat exchanger of the so-called "Demonstration Reactor Phase I Design Study" was quantitatively evaluated; the allowable stress level calculated by elastic analysis can be roughly doubled and the design life of 60 years was envisaged. Moreover, a new concept of design standard that is indispensable to utilize the above promising technologies in actual plant designs without decreasing reliability. The new system of codes and standards must cover not only design evaluation but also specification and fabrication of structural material, fabrication inspection, operation and maintenance. At the same time, it must show quantitatively the safety margins that must be made and the way to achieve it so that the cost be minimum as well.

JAEA Reports

Study on optimaI vertical isolation characteristics

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JNC TN9400 2000-060, 168 Pages, 2000/05

JNC-TN9400-2000-060.pdf:4.09MB

Optimal vertical isolation characteristics were studied for the structural concept of vertical seismic isolation system, which uses a common deck and a set of large coned dish springs. Four kinds of earthquake wave and three kinds of artificial seismic wave were used. The earthquake response analysis of a base isolated building was carried out considering some ground conditions and some vertical vibration characteristics of the building isolator. Floor response and acceleration time history at the vertical isolation level were arranged. Using the acceleration time history as a seismic input, the earthquake response analysis of the vertical isolation system according to single degree of freedom model was carried out. Linear analysis and non-linear analysis were made. ln the linear analysis, vertical isolation frequency was examined within 0.8 to 2.5 Hz, and damping ratio was examined within 2 to 60%. ln the non-linear analysis, it was examined within vertical isolation frequency 0.5 to 5Hz, which depended only on the rigidity of the coned disk spring, rigidity ratio of the damping devise 1 to 20 and yield seismic intensity of the damping devise 0.01 to 0.2. As the optimal vertical isolation characteristics of the system, the criterion of largest relative displacement, maximum acceleration and maximum value of the floor response acceleration between 5 to 12Hz was set, the combination region of the appropriate parameter were examined. ln case of largest relative displacement 50mm, acceleration response magnification of 0.75, floor response magnification of 0.33 were used as a criterion, from the result of the linear analysis, vertical frequency was set at 0.8 to l.2 Hz, and by combining the damping ratio over 20 %, it was proven that appropriate vertical isolation characteristics were obtained. The result of the non-linear analysis showed that the combination of the coned disk spring of vertical frequency 0.8 to 1.0 Hz and the damping element of rigidity ...

JAEA Reports

Study on sodium coolant loop-type reactor; Parametric study on maximum thermal stress depending on routing dimension of piping system

Tsukimori, Kazuyuki; Furuhashi, Ichiro*

JNC TN9400 2000-049, 93 Pages, 2000/03

JNC-TN9400-2000-049.pdf:2.82MB

lt is one of the important key points to reduce thermal stress of the primary piping system in the design of sodium coolant loop-type FBR plants. The objectives of this study are to understand the characteristics of the thermal stresses in the simple S-shaped hot leg piping systems which run from the outlet nozzle of the reactor vessel (R/V) to the inlet nozzle of the intermediate heat exchanger (IHX), and to propose some recommendable routings of piping systems. Results are summarized as follows. (1)Generally, the thermal stresses in elbows are severer than those at nozzles. The tendency was observed that the stress in elbow decreases with the increase of the distance between the outlet nozzle of R/V and the inlet nozzle of IHX and also the distance between the outlet nozzle of R/V and the liquid surface level. (2)lt is expected to reduce thermal stresses in elbow to big extent by adopting super 90 degree elbows. Therefore, in these cases the dimension region which satisfies the allowable stress is broad compared with that in the case of the conventional 90 degree elbow. (3)The stress estimations in elbow based on 'MITl notice No.501' become excessively large compared with the results by FEA using shell elements, when the maximum stress occurs at the end of elbow. ln these cases, the estimation can be rationalized by replacing the maximum stress by the mean of stresses at the end and at the middle of the elbow. (4)Two routings with 105 degree elbows are recommended. 0ne has the advantage from the view point of reduction of length of pipe and the other does from the view point of reduction of thermal stresses, compared with the routing with 90 degree elbows.

JAEA Reports

Analysis of weld residual stresses by FINAS (1)

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JNC TN9400 2000-047, 114 Pages, 2000/03

JNC-TN9400-2000-047.pdf:8.25MB

Prediction of weld residual stresses by a general finite element code is beneficial to the improvement of the accuracy of integrity assessment and residual life assessment of FBR plants. This reports develops an evaluation method of weld residual stresses using FINAS. Firstly, we suggested a basic procedure derived from parametric analyses with a simple weld joint model. The procedure can be summarized as follows: (1)For heat conduction analysis, prepare different models corresponding to the number of layers to be modeled. Hand over the analytical results to the following model. (2)Use multi-linear stress-strain curves for modeling the stress-strain response of base metal and weld metal. Use the isotropic hardening rule. (3)When metals are melt, use a user-subroutine to keep stresses from arising. (4)Put the thermal expansion coefficient as zero when heat is being input. Then, using the above procedure and TIG welding, we predicted the weld residual stresses of plate and tube. The results agreed well with the other reports, showing the suggested procedure was reasonable.

JAEA Reports

Interpretation of SSOUFFLE experiment : Comparison of the JNC and CEA approaches

Laurent LE BER*; kasahara, Naoto

JNC TN9400 2001-011, 14 Pages, 2000/02

JNC-TN9400-2001-011.pdf:0.37MB

For considering strength reduction of weldments in elevated temperature components, CEA and JNC have developed design evaluation procedures, Both procedures were applied to the same benchmark problems and their results were compared under EJCC contract. One of benchmarks that provided by CEA is creep-fatigue evaluation of plates subjected to cyclic bending. The objective of this problem is comparison of both material data and strength reduction evaluation of welded joints. When applied to SOUFFLE experiments, JNC and CEA evaluation procedures were clarified to give adequate predictions. Comparison of material data between Japanese 316FR and French 316L(N) showed such similar characteristics as strain hardening of base metai, non-strain hardening of weld metal and approximately the same fatigue strength of weld metal with its base metal. Both fatigue strength approaches were different, since JNC considers material difference between base and weld metal for strength reduction of welded joints and CEA evaluates fatigue strength reduction of weld metal. Concerning creep strength, both of JNC and JEA take strength reduction of weld metal into account.

JAEA Reports

Interpretation of TTS experiment : Comparison of creep fatigue evaluation methods of weldment

kasahara, Naoto; Laurent LE BER*

JNC TN9400 2001-010, 27 Pages, 2000/01

JNC-TN9400-2001-010.pdf:0.63MB

For considering strength reduction of weldments in elevated temperature components, CEA and JNC have developed design evaluation procedures. Both procedures were applied to the same benchmark problems and their results were compared under EJCC contract. One of benchmarks that provided by JNC is creep-fatigue evaluation of a welded vessel subjected to cyclic thermal transient loading. The objective of this problem is comparison of total strength evaluation methods of base metal and welded joints against actual loading conditions. This report compared results of the JNC problem evaluated by both procedures from view points of material properties, strength evaluation of base metals, and strength reduction evaluation of welded joints. Main differences of procedures were found in strain concentration evaluation methods of base metal, initial stress evaluation methods of relaxation, fatigue strength reduction factors of weldments, and creeep strength reduction factor of weldments. Both of CEA and JNC procedures were confirmed to be conservative for weldments of 316FR.

JAEA Reports

JNC contribution to the Benchmark Problem on thermal transient strength evaluation of a welded vessel

kasahara, Naoto

JNC TN9400 2001-009, 55 Pages, 2000/01

JNC-TN9400-2001-009.pdf:3.11MB

Fatigue and creep-fatigue strength of welded joints are lower than base metals, when applied to elevated temperature components subjected to cyclic thermal transient loading. CEA and JNC have developed design evaluation procedures for considering strength reduction of weldments in elevated temperature components. It was planned to compare both procedures based on the same benchmark problems under EJCC contract. One of benchmarks provided by CEA is fatigue and creep-fatigue evaluation of welded plates due to reverse bending at 550$$^{circ}$$C. Another problem by JNC is creep-fatigue evaluation of a welded vessel due to cyclic thermal transient loading. Point of view of the later problem is comparison of total strength evaluation of base metal and welded joints against actual loading conditions. This report describes details of the TTS experiments and defines the JNC benchmark problem.

JAEA Reports

Frequency response function method with constraint efficiency factors for Hot/Cold spot problems

Kasahara, Naoto

JNC TN9400 2001-008, 80 Pages, 2000/01

JNC-TN9400-2001-008.pdf:1.67MB

Temperature fluctuation from incomplete fluid mixing induces typically bending plus peak stress across wall thickness. For this stress mode, author has developed the frequency response function to establish design-by-analysis methodology for this phenomenon. On the other hand, it is pointed out that hot and cold spots appear near T-junctions in piping systems, Those induce other stress modes from three-dimensional temperature distributions. This report describes the extension of the frequency response method to hot and cold spot problems by introducing constraint efficiency factors. Its applicability was validated by application to a hot spot near the T-junction of PHENIX secondary piping system.

JAEA Reports

Benchmark problems on thermal striping evaluation of FAENA and TIFFSS sodium experiments

kasahara, Naoto; Lejeail, V.*

JNC TN9400 2001-006, 57 Pages, 2000/01

JNC-TN9400-2001-006.pdf:3.17MB

Since thermal striping is a coupled thermohydraulic and thermomechanical phenomenon, sodium mock-up tests were usually required to confirm structural integrity. CEA and JNC have devdoped evaluation procedures of thermal striping to establish design-by-analysis methodology for this phenomenon. Attenuation of temperature and stress amplitude was one of the most important factors in the integrity assessment. Since this attenuation depends on frequencies of temperature fluctuation, benchmark problems based on frequency control tests were planned to confirm above procedures. One of benchmarks Provided by CEA is temperature and fatigue evaluation of tubes and plates due to channel flows. Another problem from JNC is the same evaluation of plates subjected to vertical jets. This report explains details of both experiments and defines the benchmark problems.

JAEA Reports

Frequency response function method for evaluation of thermal striping phenomena

kasahara, Naoto

JNC TN9400 2001-005, 40 Pages, 2000/01

JNC-TN9400-2001-005.pdf:0.75MB

A rational analysis method of thermal stress induced by fluid temperature fluctuation is developed, by utilizing frequency response characteristics of structures. High frequency components of temperature fluctuation are attenuated in the transfer process from fluids to structures. Low frequency components hardly induce thermal stress since temperature homogenization in structures. Based on investigations of frequency response mechanism of structures to fluid temperature, a frequency response function of structures was derived, which can predict stress amplitudes on structural surfaces from fluid temperature amplitudes and frequencies. This function is formulated by separation of variables, and is composed of an effective heat transfer function and an effective thermal stress one. The frequency response function method appears to evaluate thermal stress rationally and to give information on damageable frequency range of structures.

JAEA Reports

Evaluation of random temperature fluctuation problems with frequency response approach

Lejeail, V.*; kasahara, Naoto

JNC TN9400 2001-004, 82 Pages, 2000/01

JNC-TN9400-2001-004.pdf:1.68MB

Since thermal striping is a coupled thermohydraulic and thermomechanical phenomenon, sodium mock-up tests were usually required to confirm structural integrity. Authors have developed the frequency response function to establish design-by-analysis methodology for this phenomenon. Applicability of this method to sinusoidal fluctuation was validated through two benchmark problems with FAENA and TIFFSS facilities under EJCC contract. This report describes the extension of the frequency response method to random fluctuations. As an example of application, fatigue strength of a Tee junction of PHENIX secondary piping system was investigated.

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