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Journal Articles

Numerical simulation of thermal striping phenomena for fundamental validation and uncertainty quantification; Application of least square version GCI and area validation method to impinging jet in a T-Junction piping system

Tanaka, Masaaki

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 14 Pages, 2018/10

A numerical simulation code MUGTHES has been developed to estimate high cycle thermal fatigue in SFRs. In development of numerical simulation code, verification, validation, and uncertainty quantification (VVUQ) are indispensable. In this study, numerical simulation at impinging jet condition in the WATLON experiment which was the water experiment of a T-junction piping system was performed for the fundamental validation. Based on the previous studies, the simplified least square version GCI method and the area validation metrics were employed as reference methods to quantify uncertainty and to measure the degree of difference between the numerical and the experimental results, respectively. Through the examinations, the potential applicability of the MUGTHES to the thermal striping phenomena was indicated and requirements of modification in the simulation was suggested in accordance with the uncertainty values.

Journal Articles

Development of numerical estimation method using spatial connection methodology for thermal striping in upper plenum of reactor vessel of an advanced loop-type sodium-cooled fast reactor in Japan

Tanaka, Masaaki; Murakami, Satoshi*

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 10 Pages, 2017/07

Thermal striping on the core instrumentation plate (CIP) around the primary control rod (PCR) and backup control rod (BCR) channels and the radial blanket fuel assemblies (RBAs) may be caused. Since the interaction between neighbor areas exists in the UIS and the cold sodium flowing from the RBA is affected by the external flow around the UIS, a spatial connection method consisting of the numerical model for the whole upper plenum and the local target area has been developed. The numerical results were compared with the experimental results to confirm applicability of the method to the practical problem. And, sensitivity of mesh arrangement to the numerical results was discussed by using wide and narrow area models with two different spatial resolutions in each model. Through the examinations, appropriate local model for the spatial connection mothed could be proposed.

Journal Articles

Fundamental validation of fluid-structure thermal interaction simulation code for thermal striping in sodium-cooled fast reactors with parallel triple jets mixing experiments

Tanaka, Masaaki; Kobayashi, Jun; Nagasawa, Kazuyoshi*

Proceedings of OECD/NEA & IAEA Workshop on Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation (CFD4NRS-6) (Internet), 12 Pages, 2016/09

A numerical simulation code named MUGTHES which can deal with conjugate heat transfer problem between the fluid and the structure parts has been developed in order to predict the thermal response in the structure for estimation of the thermal fatigue issue. To perform fundamental validation of the MUGTHES, the benchmark simulation was considered using the experiment of planar triple parallel jets mixing sodium test (PLAJEST). Since it was known by literatures that three representative flow mixing patterns were shown in accordance with the velocity rate of the side jets to the center jet, three typical experimental conditions in the PLAJEST were employed as boundary conditions for the benchmark. Through the numerical simulations, applicability of the large eddy simulation (LES) approach with the standard Smagorinsky model to simulate thermal striping phenomena was confirmed.

Journal Articles

Development of numerical estimation method for high cycle thermal fatigue by coupling of fluid-structure thermal interaction simulation and thermal stress analysis

Tanaka, Masaaki; Miyake, Yasuhiro*

Nippon Kikai Gakkai M&M 2015 Zairyo Rikigaku Kanfarensu Koen Rombunshu (Internet), 3 Pages, 2015/11

A prototype coupling method consisting of the fluid-structure thermal interaction simulation code MUGTHES and the structural thermal stress analysis code FINAS with interface program MUFIN has been developed in order to estimate the thermal fatigue in the SFRs. As a fundamental validation of the coupled method, it was applied to the water experiment for thermal mixing phenomena in a T-junction piping system. In the experiment, thermal interaction between the fluid and the structure made of aluminum installed to the branch pipe side wall was considered. Through the numerical simulations, applicability of the coupled method was confirmed.

Journal Articles

Numerical simulation of thermal striping phenomena in a T-junction piping system for fundamental validation and uncertainty quantification by GCI estimation

Tanaka, Masaaki; Miyake, Yasuhiro*

Mechanical Engineering Journal (Internet), 2(5), p.15-00134_1 - 15-00134_20, 2015/10

In this study, numerical simulation for the water experiment of a T-junction piping system (T-pipe) was carried out to validate the MUGTHES and to investigate the relation between the mechanism of temperature fluctuation generation and the unsteady motion of large eddy structures. In the numerical simulation, the large eddy simulation (LES) approach with standard Smagorinsky model was employed as eddy viscosity model to simulate large scale eddy motion in the T-pipe. As for uncertainty quantification in the validation process, the modified method of the Grid Convergence Index (GCI) estimation based on the least squire version could successfully quantify uncertainty. Through the numerical simulations, it could be found that the thermal mixing phenomena in the T-pipe were caused by the mutual interaction of the necklace-shaped vortex around the wake from the front of the branch jet, the horseshoe-shaped vortex and the Karman's vortex motions in the wake.

Journal Articles

Benchmark analysis of thermal striping phenomena in planar triple parallel jets tests for fundamental validation of fluid-structure thermal interaction code for sodium-cooled fast reactor

Tanaka, Masaaki; Nagasawa, Kazuyoshi*

Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.6650 - 6663, 2015/08

For the fundamental validation of fluid-structure thermal interaction code (MUGTHES), numerical simulations for the planar triple parallel jets tests in WAJECO and PLAJEST have been conducted as the benchmark analysis. In comparison between the numerical results and the provided experimental results, thermal mixing process and large-scale eddy structures generated in the triple jets mixing and the relation between temperature fluctuation generation and large-eddy structures were revealed. And also, the attenuation process of temperature fluctuation from the fluid to the structure was indicated.

Journal Articles

Establishment of numerical estimation method for high cycle thermal fatigue estimation in sodium-cooled fast reactor, 1; Conceptual model development for numerical estimation by using PIRT method

Tanaka, Masaaki

Dai-20-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.55 - 58, 2015/06

Numerical estimation method for high cycle thermal fatigue on a structure has been developed in JAEA. In development of numerical simulation codes and application of the codes to plant design, implementation of verification and validation (V&V) is indispensable. A procedure called as V2UP (Verification and Validation plus Uncertainty quantification and Prediction) has been made by referring to the existing guidelines on V&V. The PIRT (Phenomena Identification and Ranking Table) method based on the nine-step process used by the USNRC for the next generation nuclear plant development was employed at the first step of the V2UP. Through the first step of the V2UP with PIRT method, the conceptual model for the numerical estimation of high cycle thermal fatigue was successfully constructed.

Journal Articles

Numerical investigation on thermal striping phenomena in a T-junction piping system

Tanaka, Masaaki; Miyake, Yasuhiro*

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 13 Pages, 2014/07

In this study, numerical simulation for the WATLON experiment which was the water experiment of a T-junction piping system (T-pipe) was carried out to validate the MUGTHES and to investigate the relation between the mechanism of temperature fluctuation generation and the unsteady motion of large eddy structures. In the numerical simulation, the large eddy simulation (LES) approach with standard Smagorinsky model was employed as eddy viscosity model to simulate large scale eddy motion in the T-pipe. As for uncertainty quantification in the validation process, the modified method of the Grid Convergence Index (GCI) estimation based on the least squire version could successfully quantify uncertainty. Through the numerical simulations, it was indicated that the fine mesh arrangement could improve the temperature distribution in the wake. It could be found that the thermal mixing phenomena in the T-pipe were caused by the mutual interaction of the necklace-shaped vortex around the wake from the front of the branch jet, the horseshoe-shaped vortex and the Karman's vortex motions in the wake.

Journal Articles

Investigation of uncertainty quantification procedure in validation process of fluid-structure thermal interaction simulation code

Tanaka, Masaaki; Ohno, Shuji

Dai-19-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.247 - 250, 2014/06

A procedure combined V&V of the code and numerical prediction process called as V2UP (Verification and Validation plus Uncertainty quantification and Prediction) has been developed by referring to the existing guidelines. By using numerical results by MUGTHES for the WATLON experiment which was a water experiment to investigate thermal mixing phenomena in a T-junction piping system, applicability of the GCI estimation method and the area validation metric (AVM) method and the modified one (MAVM) in the V2UP were examined. Through the examinations, it was found that the GCI estimation by using the modified least-square version was applicable and the AVM and the MAVM methods were applicable if transient data were obtained in the experiment.

JAEA Reports

lnvestigation of thermal-hydraulic issues resulting in the use of various coolants

; Yamaguchi, Akira

JNC-TN9400 2000-056, 150 Pages, 2000/05

JNC-TN9400-2000-056.pdf:6.67MB

[Purpose] The work was performed to make clear thermal-hydraulic issues resulting in the use of various coolants for fast reactors. [Method] Plant design features due to a use of working fluid other than sodium and design concepts relating a simplification of safety related systems were investigated. And based on the results, quantitative evaluation was made on the topical themal-hydraulic issues. Then both thermal stratification and striping phenomena were evaluated by the used of thermo-hydraulics computer programs. [Results] (1)Thermal-hydraulic issues Topical thermal-hydraulic issues of gaseous and heavy metal cooled reactors were extracted. (a)Gas cooled reactors : natural circulation,flow-induced vibration, depressurization accident (b)Heavy metal cooled reactors : thermal stratification, flow-induced vibration, sloshing And also the thermal-hydraulic issues relating compact reactor assembly and RVACS were extracted resulting from a simplification of safety related systems. (2)Evaluation of thermal stratification and striping phenomena. The following order of affects for the phenomena was obtained: (a) Thermal stratification: CO$$_{2}$$ $$<$$ Sodium $$<$$ Lead, (b) Thermal Striping: CO$$_{2}$$ $$<$$ Lead $$<$$ Sodium

JAEA Reports

Current status and future plan for thermaI striping investigations at JNC

; kasahara, Naoto; ; ; Kamide, Hideki

JNC-TN9400 2000-010, 168 Pages, 2000/02

JNC-TN9400-2000-010.pdf:8.78MB

Thermal striping is significant issue of the structural integrity, where the hot and cold fluids give high cycle fatigue to the structure through the thermal stress resulted from the time change of temperatur distibution in the structure. In the sodium cooled fast reactor, temperature change in fluid easily transfers to the structure because of the high thermal conductivity of the sodium. It means that we have to take care of thermal striping, The thermal striping is complex phenomena between the fluid and structure engineering fields. The investigations of thermal striping are not enough to evaluate the integrity directly. That is the fluctuation intensity at the structure surface is assumed to be temperature difference between source fluids (upstream to the mixing region) as the maximum value in the design. 0therwise, the design conditions are defined by using a mockup experiment and large margin of temperature fluctuation intensity. Furthermore, such evaluation manners have not yet been considered as a design rule. Transfer mechanism of temperature fluctuation from fluid to structure has been investigated by the authors on the view points of the fluid and structure. Attenuation of temperature fluctuation was recognized as a dominant factor of thermal fatigue. We have devdoped a numerical analysis system which can evaluate thermal fatigue and crack growth with consideration of the attenuation of temperature fluctuation in fluid, heat transfer, and structure. This system was applied to a real reactor and the applicability was confirmed. Further verification is planned to generalize the system. For the higher cost performance of the fast reactor, an evaluation rule is needed, which can estimate thermal loading with attenuation and can be applied to the design. An idea of the rule is proposed here. Two methods should be prepared; one is a precise evaluation method where mechanism of attenuation is modeled, and the other is simple evaluation method where ...

JAEA Reports

Numerical Investigation on Thermal Stratification and Striping Phenomena in Various Coolants

Yang Zumao*;

JNC-TN9400 2000-009, 81 Pages, 2000/02

JNC-TN9400-2000-009.pdf:47.3MB

It is important to study thermal stratification and striping phenomena for they can induce thermal fatigue failure of structures. This presentation uses the AQUA code, which has been developed in Japan Nuclear Cycle Development Institute (JNC), to investigate the characteristics of these thermal phenomena in water, liquid sodium, liquid lead and carbon dioxide gas.There are altogether eight calculated cases with same Richardson number and initial inlet hot velocity in thermal stratification calculations, in which four cases have same velocity difference between inlet hot and cold fluid, the other four cases with same temperature difference. The calculated results show : (1) The fluid's properties and initial conditions have considerable effects on thermal stratification, which is decided by the combination of such as thermal conduction, viscous dissipation and buoyant force, etc., and (2) The gas has distinctive thermal stratification characteristics from those of liquid because for

JAEA Reports

Numerical investigation on thermal striping conditions for a tee junction of LMFBR coolant pipes (IV); Investigation on second-order moments in coolant mixing region

JNC-TN9400 2000-008, 323 Pages, 2000/02

JNC-TN9400-2000-008.pdf:25.2MB

This rport presents numerical results on theemal striping characteristics at a tee junction of LMFBR coolant pipe, carried out using a direct numerical simulation code DINUS-3. In the numerical investigations, it was considered a tee junction system consisted of a main pipe (1.33 cm$$^{I.D.}$$) with a 90$$^{circ}$$ elbow and a branch pipe, and four parameters, j.e., (1)diameter ratio $$alpha$$ between both the pipes, (2)flow velocity ratio $$beta$$ between both the pipes, (3)angle $$gamma$$ between both the pipes, and (4)Reynolds number Re. From the numerical investigations, the following characteristics were obtained: (1)According to the decreasing of the diameter ratio, significant area of second-order moments was expanded in the fixed condition of $$beta$$=1.0. (2)Significant second-order moments area was expanded for the increasing of the flow velocity ratio $$beta$$ specified by varying of the main pipe velocity in the case of a $$alpha$$ = 1.0 constant condition. 0n the other hand, the area was expanded for the decreasing of the velocity ratio $$beta$$ defined by varying of the branch pipe velocity in the case of a $$alpha$$ = 3.0 constant condition. (3)Maximum second-order moments values were generated in the case of $$gamma$$ = 180$$^{circ}$$ due to the influence of interactions between main pipe flows and jet flows from the branch pipe. (4)According to the increase of Reynolds number, significant area of second-order moments was expanded due to the activation of turbulence mixing in the main pipe.

JAEA Reports

Thermal striping an experiental investigation on mixing of jets; Part III Remaining hydrodynamic results from initial experiments

Tokuhiro, Akira; Kimura, Nobuyuki;

JNC-TN9400 2000-014, 86 Pages, 1999/06

JNC-TN9400-2000-014.pdf:11.72MB

Experiments were performed using the WAJECO facility to investigate the thermohydraulic mixing of multiple jets flowing out of a LMFBR core. Mixing is the root of the thermal striping problem. The multiple jets are typically at different velocities and temperatures and may induce thermal stresses upon components they impinge. In our study we modeled the mixing of three vertical jets, the central at a lower temperature than the two adjacent jets at equal temperatures. The jets are quasi-planar. The parameters were the average exit jet velocities (Uo,av) and the temperature difference between the "cold" and "hot" jets ($$Delta$$Thc=Thot-Tcold). Measurements of the liquid velocity, initially using laser Doppler velocimetry (LDV) and later ultrasound Doppler velocimetry (UDV), for both our reference single-jet and the triple-jet configuration, comprised Phase I of the experiments (up to 1994). Two reports (TN9410 96-181 and TN9410 96-296; in Japanese) reported on the hydraulic and heat tra

JAEA Reports

Low temperature creep and stress corrosion cracking tests of rupture disk (Alloy600)

; *; Yoshida, Eiichi; Aoto, Kazumi

JNC-TN9400 2000-011, 33 Pages, 1999/03

JNC-TN9400-2000-011.pdf:13.45MB

The damage was observed in rupture disk for the A-loop superheater of sodium-water reaction products releasing system for MONJU on March 3, 1998. Low temperature creep and stress corrosion cracking tests were carried out as the causes investigation of the damage. As the result, the followings are clarified. (1)The possibility that low temperature creep is the principal damage is small. (2)The stress corrosion cracking under NaOH environment due to the reaction of Na vapor and moisture condensed on the surface of glass beads as remains is the most probable cause on the damage. (3)Comparatively many glass beads remained in damaged surface. The gap between rupture disk and vacuum support was narrower than other parts, and they were not directly exposed to the Na vapor for a long time. The above factors caused the perfect intergranular cracking by stress corrosion. Since NaOH was chemically changed into the harmless Na$$_{2}$$O on the location except for damaged zone by full Na vapor, the stress corrosion cracking was not generated.

JAEA Reports

Development of structural response diagram approach to evaluation of thermal stress caused by thermal striping

Kasahara, Naoto; Yacumpai, A.*; Takasho, Hideki*

JNC-TN9400 99-019, 34 Pages, 1999/02

JNC-TN9400-99-019.pdf:0.97MB

At incomplete mixing area of high temperature and low temperature fluids near the surface of structures, temperature fluctuation of fluid gives thermal fatigue damage to wall structures. This thermohydraulic and thermomechanical coupled phenomenon is called thermal striping, which has so complex mechanism and sometimes causes crack initiation on the structural surfaces that rational evaluation methods are required for screening rules in design codes. In this study, frequency response characteristics of structures and its mechanism were investigated by both numerical and theoretical methods. Based on above investigation, a structural response diagram was derived, which can predict stress amplitude of structures from temperature amplitude and frequency of fluids. Furthermore, this diagram was generalized to be the Non-dimensional structural response diagram by introducing non-dimensional parameters such as Biot number, non-dimensional frequency, and non-dimensional stress. The use of the Non-dimensional structural response diagram appears to evaluate thermal stress caused by thermal striping, rapidly without structural analysis, and rationally with considering attenuation by non-stationary heat transfer and thermal unloading. This diagram can also give such useful information as sensitive frequency range to adjust coupled thermohydraulic and thermomechanical analysis models taking account of four kinds of attenuation factors: turbulent mixing, molecular diffusion, non-stationaly heat transfer, and thermal unloading.

JAEA Reports

Numerical investigation on thermal striping conditions for a tee junction of LMFBR coolant pipes (II); Investigation for the MONJU EVST tee junction

PNC-TN9410 98-044, 47 Pages, 1998/06

PNC-TN9410-98-044.pdf:6.69MB

Thermal striping phenomena characterized by stationary random temperature fluctuations are observed in the region immediately above the core exit of liquid-metal-cooled fast breeder reactors (LMFBRs) due to the interactions of cold sodium flowing out of a control rod (C/R) assembly and hot sodium flowing out of adjacent fuel assemblies (F/As). Therefore the in-vessel components located in the core outlet region, such as upper core structure (UCS), flow guide tube, C/R upper guide tube, etc., must be protected against the stationary random thermal process which might induce high-cycle fatigue. In this study, thermal striping conditions at the tee junction in the MONJU EVST system (maximum temperature difference : 110 $$^{circ}$$C, Velocity ratio between main and branch pipes : 0.25) were investigated numerically by the use of computer programs. From the investigations, the following results have been obtained: (1) Effects of the secondaly flows generated by the existence of 90$$^{circ}$$ elbow located at upstream position of the tee junction were negligeble, because the flow velocity in the main pipe is 0.25 of the flow velocity in the branch pipe. (2) A ration between maximum and effective amplitudes of the temperature fluctuations calculated by the DINUS-3 code was 3.18. It was concluded that the value 6.0 as the ratio used in the integrity evaluation of the EVST system is a coservative side. (3) There was a limit in ability of a time-averaged multi-dimensional code AQUA, in the evaluation of thermal striping phenomena with recirculation flows. One of the reasons was considered that the local equilibrium of turbulence flows was not established in this tee junction problem.

JAEA Reports

Development of analytical model for evaluating temperature fluctuation in coolant(XI); Validation of the evaluation model for thermally fluid-structure interaction phenomena

PNC-TN9410 97-039, 187 Pages, 1997/05

PNC-TN9410-97-039.pdf:11.45MB

A numerical evaluation system, which is consisted of four codes, AQUA, DINUS-3, THEMIS and BEMSET has been developed for thermal striping phenomena. To validate the system for the phenomena, thermally fluid - structure interaction analysis was carried out using a existing sodium experiment of parallel impinging jet simulating the outlet region of an LMFBR core. Calculational results on the RMS values of temperature fluctuation, the histograms of temperature amplitudes and frequencies, the auto-power spectral density distributions of temperature fluctuations and the damping characteristics of temperature fluctuations showed good agreement with the measured values under the test conditions of various flow velocity. From the comparisons with the experimental data, it was concluded that the numerical evaluation system is applicable to the evaluation of thermally fluid - structure interaction phenomena related to the thermal striping.

Oral presentation

Study on high cycle thermal fatigue at a bottom of UIS in a sodium-cooled fast reactor; Modified countermeasures for temperature fluctuation at a bottom of UIS

Kobayashi, Jun; Kimura, Nobuyuki*; Tanaka, Masaaki; Kamide, Hideki; Oyama, Kazuhiro*; Watanabe, Osamu*

no journal, , 

no abstracts in English

Oral presentation

Numerical investigation of thermal striping on core instrumentation plate in upper plenum of JSFR with spatial connection method

Tanaka, Masaaki; Murakami, Satoshi*

no journal, , 

Thermal striping on the core instrumentation plate (CIP) around the primary control rod (PCR) and backup control rod (BCR) channels and the radial blanket fuel assemblies (RBAs) may be caused. Since the interaction between neighbor areas exists in the UIS and the cold sodium flowing from the RBA is affected by the external flow around the UIS, a spatial connection method consisting of the numerical model for the whole upper plenum and the local target area has been developed. The numerical results were compared with the experimental results to confirm applicability of the method to the practical problem. And, sensitivity of mesh arrangement to the numerical results was discussed by using wide and narrow area models with two different spatial resolutions in each model. Through the examinations, appropriate local model for the spatial connection mothed could be proposed.

25 (Records 1-20 displayed on this page)