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Uchibori, Akihiro; Watanabe, Akira*; Takata, Takashi; Ohshima, Hiroyuki
Nihon Kikai Gakkai Rombunshu (Internet), 84(859), p.17-00394_1 - 17-00394_6, 2018/03
For assessment of the wastage environment under tube failure accident in a steam generator of sodium-cooled fast reactors, a mechanistic computer code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium-water chemical reaction has been developed. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method was developed and introduced into the SERAPHIM code to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Validity of the unstructured mesh-based SERAPHIM code was investigated through the analysis of an underexpanded jet experiment. The calculated pressure profile showed good agreement with the experimental data. Numerical analysis of water vapor discharging into liquid sodium was also performed. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium-water reaction phenomenon.
Umeda, Ryota; Shimoyama, Kazuhito; Kurihara, Akikazu
JAEA-Technology 2017-018, 70 Pages, 2017/08
JAEA-Technology-2017-018.pdf:9.67MB
In case of the water leak into sodium in a SG of SFRs due to tube failure, reaction jet is formed by sodium-water reaction with exothermic heat. The reaction jet forms highly alkaline environment with high temperature and high pressure, which cause local thinning of adjacent heat transfer tubes (target wastage). In this report, for the purpose of elucidation of target wastage, the authors developed the experimental apparatus and experimental technique which enable the separate evaluation of wastage influence factors, including temperature, impingement velocity, reagent ratio and so on by using high temperature sodium hydroxide as major reaction product and sodium monoxide as secondary reaction product. In addition, the impingement corrosion experiments have been conducted by using high temperature reagents (NaOH and Na
O). Based on the corrosive data, authors quantitatively evaluated the influence factors of wastage and formulated the average corrosive equations.
Uchibori, Akihiro; Yanagisawa, Hideki*; Takata, Takashi; Kurihara, Akikazu; Hamada, Hirotsugu; Ohshima, Hiroyuki
JAEA-Research 2017-007, 61 Pages, 2017/07
JAEA-Research-2017-007.pdf:4.3MB
For safety assessment of a steam generator of sodium-cooled fast reactors, it is necessary to evaluate the possibility of occurring tube failure propagation and of water leak rate under sodium-water reaction accident. In the previous studies, a computer code called LEAP-II calculating a wastage-type failure propagation and the water leak rate during long-time event progress was developed. In this study, a numerical method to evaluate the possibility of occurring overheating rupture was introduced into the LEAP-II code to expand application range of this code. The completed code is called LEAP-III. The test analysis on a tube bundle configuration demonstrated that the overheating rupture model could provide conservative prediction.
Umeda, Ryota; Kurihara, Akikazu; Shimoyama, Kazuhito
JAEA-Technology 2016-030, 50 Pages, 2016/12
JAEA-Technology-2016-030.pdf:5.22MB
In case of tube failure of a steam generator in sodium-cooled fast reactors, the reaction jet with high temperature and high velocity under highly alkaline environment is formed by cited exothermic reaction (sodium-water reaction). When the high temperature reaction jet covers the adjacent tubes, the material strength of tube decreases in the high temperature condition, and the adjacent tube may be swollen and failed by inner pressure (overheating tube rupture). For evaluation of the overheating tube rupture, tube failure is judged by comparison the hoop stress loaded by inner pressure with stress strength standard defined as creep strength depending on tube temperature. Thus, it is important to confirm the validation of this failure criterion based on the findings obtained in the simulated experiment of overheating tube rupture. In this report, for consideration on the validation of the failure criteria and elucidation on the failure mode and strength characteristics of failure, the authors carried out the rapid heating rupture experiment for the thin single and double-walled 9Cr steel tubes at high temperature up to 1500 K by using TRUST-2 rig in the Japan Atomic Energy Agency.
Akabane, Masaaki*; Horiki, Sachiyo*; Osakabe, Masahiro*; Koizumi, Yasuo; Uchibori, Akihiro; Ohno, Shuji; Ohshima, Hiroyuki
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 7 Pages, 2015/05
Behavior of liquid droplets in a high-velocity gaseous jet was experimentally investigated to provide validation data for the evaluation method of sodium-water reaction phenomenon. The visualization experiment on the entrained liquid droplets in the air jet submerged in a water pool was carried out. Filament-like wisps from the wavy gas-liquid interface were observed. The wisps were broken off and entrained into the air jet. The velocity of the entrained liquid droplets was estimated from an image processing. The axial velocity of the liquid droplets increased as the air inlet velocity increased. Acceleration behavior of the liquid droplets was also confirmed quantitatively.
Uchibori, Akihiro; Ohshima, Hiroyuki
Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 6 Pages, 2014/11
A computer code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium-water chemical reaction has been developed to evaluate wastage environment under tube failure accident in a steam generator of sodium-cooled fast reactors. In this study, the numerical model for liquid droplet entrainment and its transport was developed. The applicability of the model was investigated through the analysis of the basic experiment. It was demonstrated that our numerical model could reproduce the time to end of entrainment and the pressure variation during the occurrence of entrainment.
Jang, S.*; Takata, Takashi; Yamaguchi, Akira*; Uchibori, Akihiro; Kurihara, Akikazu; Ohshima, Hiroyuki
Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 8 Pages, 2014/11
Numerical quantification of the self-wastage phenomenon has been carried out using a multi-dimensional computational code: SERAPHIM. The width of the completely enlarged crack was investigated in this study. Several steps of numerical calculations were devised to reproduce transient self-wastage phenomenon caused by Sodium Water Reaction (SWR). In the analyses, 2-dimensional calculation was carried out to obtained thermal hydraulic properties in the reaction zone. The wastage amount was evaluated based on hypothetical Arrhenius equation by using the temperature and molar concentration of Sodium hydroxide. New analytical grid was created by exchanging the solid cells to fluid cells in the reaction based on the wastage amount evaluation. These series of procedure have been repeated. The width and the shape of the enlarged crack showed good agreement with the experimental results.
Okamoto, Koji*; *
JNC TY9400 2000-016, 90 Pages, 2000/06
JNC-TY9400-2000-016.pdf:2.53MB
no abstracts in English
; 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 700
C 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.
Tanabe, Hiromi; Hamada, Hirotsugu
PNC TN9410 91-028, 14 Pages, 1991/01
A COMPUTER CODE,SWACS,WAS DEVELOPED TO ANALYZE A LARGE LEAK SODIUM-WATER REACTION EVENT IN AN LMFBR STEAM GENERATOR. THE JAPANESE PROTOTYPE REACTOR,MONJU,HAS A COVER GAS SPACE IN ITS STEAM GENERATOR BUT DIFFERENT DESIGNS ARE ALSOCONSIDERED FOR A FUTURE LARGER PLANT. THEREFORE,SWACS WAS MODIFIED TO ANALYZE THESODIUM-WATER REACTION EVENT UNDER SUCH VARIOUS DESIGNS. SO FAR THE CALCULATIONALMODULE OF AN INITIAL SPIKE PRESSURE AND ITS PROPAGATION TO IHTS WAS IMPROVED AND THERESULTS WERE COMPARED WITH THE DATA FROM LLTR AT ETEC, U.S.A. AND WATER-EXPLOSIVE SIMULATION TESTS AT PNC,JAPAN. THE COMPARISON REVEALED A FAIRLY GOODAGREEMENT BETWEEN THE TESTS AND THE ANALYSES. FOLLOWING THE VALIDATION STUDY,SWACS WAS USED FOR THE APPLICATION ANALYSIS TO COMPARE THE PRESSURE BEHAVIORBETWEEN THE COVER-GAS TYPE AND THE NO-COVER-GAS TYPE STEAM GENERATOR OF A FUTURELARGER PLANT. THE ANALYSIS CLARIFIED THE APPLICABILITY OF SWACS TO SUCH A DESIGN STUDYFROM A VIEWPOINT OF SUPPRESSING THE SWR PRESSURE.
*; *; Kuroha, Mitsuo
PNC TN9410 86-023, 112 Pages, 1986/03
It is essential to clarify wastage behavior of a heat transfer tube in a sodium-water reaction in order to analyze a water leakage incident in a steam generator of LMFBR Monju. There fore wastage tests in small and intermediate leak ranges were conducted for austenitic stainless steel JIS 
SUS321 of a Monju superheater tube material by use of Small Leak Sodium-Water Reaction Test Loop (SWAT-2) and Large Leak Sodiam-Water Reaction Test Rig (SWAT-1). In the tests, a water leak rate, a distance from a leak nozzle to a target tube, and a sodium temperature were varied as empirical parameters. Test Results are as follows: (1)In the small 1eak range (0.1
10g/sec), the wastage rate of SUS321 depends on L/D and has maximum value at L/D of 20 to 30 ; where L ls distance from the nozzle to the target and D is a nozzle diameter. Since the maximun wastage rate of SUS321 is about half as high as that of SUS304, SUS321 is more resistive against wastage than SUS304. (2)In the intermediate leak range (30 and 150 g/sec), the wastage rate depends on L/D and has a peak at L/D of 2050. The maximum wastage rate is quarter as high as that of 2%Cr-1Mo Steel. (3)Empirical formulas were derived from these test results concerning the relation between the wastage rate and the parameters.
*; *; *
PNC TN941 85-127, 92 Pages, 1985/08
RECT-II (the Removal test of reaction products by cold trap) was conducted by use of SWAT-3 (the Steam Generator Safety Test Facility) at PNC in order to construct the post-accident operation of steam generators of the prototype FBR Monju and a larger plant following it. In prior to the test, some amount of the sodium-water reaction products (SWRP) generated in the water injection test (Run 18) was remained in the sodium system. An objective of the test is to confirm the purifying method to remove SWRP by hot sodium circulating through a cold trap (CT). A meshless type cold trap was selected to avoid choking by impurities and to enable efficient SWRP removal. RECT-II started on April 4, 1984 and terminated on April 26 when the plugging temperature decreased to 187C. Major results obtained in the test are as follows: (1)Post-test observation revealed that the SWRP having remained at the bottom of the evaporator and the sodium outlet pipe were completely removed through the purification operation. (2)Hence, it is concluded that after the hot draining the SWRP of 14 kg-H0 remained in the sodium system out of that generated by the 42 kg-H0 injection and that almost all of the former was removed through the operation. (3)However, some amount of the hydrocarbon-oxide and SWRP in the slit articles simulating crevice and stagnant region still remained after the operation. Then it is concluded that it is insufficient to remove SWRP in crevice and stagnant region by the circulation of hot sodium. (4)A mass transfer coefficient of oxygen is evaluated as 2 
10
[g/(mm H ppm)] if the cross section of the evaporator and inner surface of the 8 inch horizontal pipe are assumed to be the entire surface area of SWRP. (5)Since the choking of the cold trap degrades the efficient SWRP removal, it is essential to develop a cold trap which hardly chokes and easily regenerates even after choking; one of answers for this request is a ...
Hamada, Hirotsugu; Uchibori, Akihiro; Ohshima, Hiroyuki
no journal, ,
For the purpose of a safety evaluation of heat transfer tube failure in the FBR steam generator, the long-term leak enlargement and propagation analysis code (LEAP-III) is under development. A model of overheating tube rupture was incorporated into LEAP-III and LEAP-III was applied to an analysis of SWAT-3 test to evaluate the applicability of the code.
Shimoyama, Kazuhito; Kurihara, Akikazu; Kikuchi, Shin; Umeda, Ryota; Ohshima, Hiroyuki
no journal, ,
Corrosion may proceed on the tube surface due to chemical reaction between sodium and water (self-wastage), in case of water/steam leak though the penetrating crack caused in the steam generator tube of sodium-cooled fast reactor. We performed the self-wastage experiments under high sodium temperature condition to evaluate the effect of wastage dimension and water leak rate on self-wastage rate in the fine crack in this report.
Umeda, Ryota; Kurihara, Akikazu; Shimoyama, Kazuhito; Kikuchi, Shin; Ohshima, Hiroyuki
no journal, ,
no abstracts in English
Uchibori, Akihiro; Ohshima, Hiroyuki
no journal, ,
A mechanistic computer program called SERAPHIM to calculate compressible multicomponent multiphase flow with sodium-water chemical reaction has been developed as one of the evaluation methods for heat transfer tube failure accident in a steam generator of sodium-cooled fast reactors. In this study, applicability of the SERAPHIM program was investigated through the analysis of the experiment on water vapor discharging into liquid sodium under the actual condition of the steam generator. The water vapor under expanded jet reacting with the ambient liquid sodium appeared in the numerical result. The high-velocity region of the entrained liquid droplets was formed around the jet. The impingement position of the liquid droplets on the target tube located above the water vapor discharging tube agreed with the position of the wastage mark confirmed in the experiment. The temperature distribution measured around the reacting jet was also successfully reproduced by the SERAPHIM program.
Ohshima, Hiroyuki; Kurihara, Akikazu; Yamaguchi, Akira*; Takata, Takashi*; Narabayashi, Tadashi*; Deguchi, Yoshihiro*
no journal, ,
When a heat transfer tube is failed in a steam generator (SG) of a sodium-cooled fast reactor (SFR), pressurized water and/or water vapor leaks into liquid sodium surrounding the tube and forms a reacting jet with high temperature and high alkali. This reacting jet might cause the secondary failure of adjacent heat transfer tubes due to wastage or over-heating tube rapture resulting in undesirable failure propagation. Therefore, the sodium-water reaction phenomenon (SWR) is one of the most important issues for the design and safety assessment of SFRs. The authors have carried out systematic experiments for the elucidation of SWR and developed a new multi-physics numerical simulation system which is based on mechanistic and theoretical modeling of SWR rather than empirical modeling and can contribute to detailed and quantitative evaluations of SWR in any types of SGs. This paper summarizes the results of four-year R&D activities.
Umeda, Ryota; Kurihara, Akikazu; Shimoyama, Kazuhito
no journal, ,
Overheating tube rupture of adjacent tubes arises from water/steam leak in steam generators of sodium-cooled fast reactors. It is very important to predict the tube wall stress (tube wall temperature) with a high degree of accuracy on evaluation of overheating tube rupture, and is crucial to estimate quantitatively material strength standard which is one of the major influencing factor. Therefore, in present study, the authors carried out tube rupture experiments with rapidly-heating which were simulated the tube thermally-affected by sodium-water reaction jet, and evaluated quantitatively failure hoop stress and failure time. Then, the authors confirmed that existing stress strength standard was applicable to thin diameter and thick-walled single tube in case of sodium-water reaction exceeding 1300C under practical steam generator operation conditions.
Umeda, Ryota; Kurihara, Akikazu; Shimoyama, Kazuhito
no journal, ,
no abstracts in English
Jang, S.*; Yamaguchi, Akira*; Takata, Takashi; Ohshima, Hiroyuki
no journal, ,
In a self-wastage phenomenon, which occurs when a quite small leak of water or water vapor occurs in a steam generator of sodium cooled fast reactor, many parameters such as a shape and rate of leakage and sodium temperature are related mutually. In the present study, DEMATEL (Decision Making Trial and Evaluation Laboratory) method is applied to choose dominant parameters in the self-wastage phenomenon.
