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Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07
Wakui, Ryohei; Kitagaki, Toru; Higuchi, Hidetoshi; Takeuchi, Masayuki; Koizumi, Kenji; Washiya, Tadahiro
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 7 Pages, 2012/07
Furukawa, Tomohiro; Hirakawa, Yasushi
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 5 Pages, 2012/07
As a preliminary investigation into the establishment of a lithium removal technique for the components used at the IFMIF, experiments were performed on the dissolution of lithium in ethanol, pure water and ethanol-water. In these experiments, lithium was immersed in the solvents, and the degree of dissolution was measured. From the obtained data, the average dissolution rate and the amount of hydrogen generated by the chemical reaction were calculated. The average dissolution rates in ethanol, pure water and ethanol-water at 30 
C were 0.01, 1.6, and 0.43 mm/min, respectively. Although the average dissolution rate increased with the testing temperature in the low-temperature range for all solvents, this increase was saturated in the high-temperature range in experiments with pure water and ethanol-water as solvents. The volume of gas collected during each experiment was in good agreement with the volume of hydrogen assumed to be generated from the chemical reaction.
Doi, Daisuke; Nakagiri, Toshio
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07
no abstracts in English
Sato, Hiroyuki; Yan, X.; Ohashi, Hirofumi; Tachibana, Yukio; Kunitomi, Kazuhiko
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 8 Pages, 2012/07
An original control strategy for VHTR gas-turbine system with dry cooling against ambient air temperature fluctuation was established in order to enable the freedom of site selection wherever desired without significant drawbacks on the performance. The operability of power conversion system and degradation of power generation efficiency were examined. A control simulation for a large ambient temperature increase was conducted by system analysis code. It was shown that the design goal can be effectively met simply by monitoring and controlling a few of key operating parameters.
Kikuchi, Shin; Seino, Hiroshi; Kurihara, Akikazu; Ohshima, Hiroyuki
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07
In this work, we studied the kinetics of Na-NaOH reaction as secondary surface reaction in the SWR by using DTA technique. Melting points of Na and NaOH, phase transition temperature of NaOH, Na-NaOH reaction temperature, and the decomposition temperature of NaH were identified from DTA curves. Na, NaOH, and Na
O as major chemical species were identified from the XRD analysis of the residues after the DTA experiment. It was inferred that NaO could be generated as Na-NaOH reaction product. Based on the measured reaction temperature, the first-order Arrhenius type rate constant of NaO generation and these related kinetic parameters were obtained by the application of kinetic laws. According to this kinetic study, it was found that NaO generation should be considered during SWR.
Takeda, Takeshi; Otsu, Iwao; Nakamura, Hideo
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 11 Pages, 2012/07
Guo, L.*; Morita, Koji*; Tobita, Yoshiharu
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07
In core disruptive accidents (CDAs), the motions and interactions of solid particles, such as refrozen fuels, disrupted pellets, etc., not only dominate fundamental behaviors of multiphase flows, but also drastically influence the process of CDAs. In the fast reactor safety analysis code, SIMMER-III, strong ineractions among solid particles in multiphase flows with rich solid particles were not taken into consideration for fluid-dynamics models of SIMMER-III. In this article, a hybrid method for multiphase flows analysis is developed by coupling the discrete element method (DEM) with the multi-fluid model of SIMMER-III. In the coupling algorithm, motions of liquid and gas phases are solved by a time-factorrization (time-splitting) method. For the solid phases, contacts among particles and interactions with fluid phases are considered through DEM. Numerical simulations of dam-break behavior with rich solid particles show reasonable agreements with corresponding experimental results. It is expected that SIMMER-III coupled with DEM could provide a promising and useful computational tool for complicated multiphase-flow phenomena with high concentration of solid particles in CDAs.
Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*; Yamano, Hidemasa; Tagami, Hirotaka; Suzuki, Toru; Tobita, Yoshiharu
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 10 Pages, 2012/07
During a hypothetical core-disruptive accident in a sodium-cooled FBR, degraded core material can form debris beds on the core-support structure and/or in the lower inlet plenum of the reactor vessel. Heat convection and vaporization of the sodium will lead ultimately to leveling the debris bed that is of crucial importance to the relocation of the molten core, the recriticality evaluation and the heat removal capability of the debris bed. There is, therefore, a great need for more studies focusing on this topic, especially the much needed numerical simulation. The debris fluidization model and the boiling regulation model are proposed and introduced into SIMMER-III. Calculations, by the modified SIMMER-III, against several representative experiments with typical self-leveling behavior have been performed and compared with the evaluated items recorded in experiments. The good agreements on these items suggest the modified SIMMER-III can simulate the self-leveling behavior with reasonable precision, especially on the onset of self-leveling, although further model improvement is necessary to represent the transient behavior of bed leveling more reasonably.
Takeuchi, Masayuki; Sano, Yuichi; Nakajima, Yasuo; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07
A long-term corrosion tendency and metal salt effect in heating nitric acid solution on corrosion behavior of titanium-5% tantalum alloy (Ti-5Ta) in hot nitric acid condensate condition were mainly researched to discuss the aging behavior of reprocessing equipments such as evaporators made of titanium or its alloy. The hot pure nitric acid solution with continuous renewing such as the nitric acid condensate condition is severe corrosion environment for their materials because of the corrosion inhibition effect from titanium ions as corrosion products or oxidizing ions in nitric acid solution. From the results of the long-term corrosion test for total 11,000 hrs, the corrosion of Ti-5Ta in the nitric acid condensate was accelerated with increase of the nitric acid concentration in the condensate. The corrosion rate was nearly constant during the immersion time and the test coupons suffered a uniform corrosion. Thus, from the viewpoints of nitric acid corrosion, the life-time of the reprocessing equipments made of titanium or its alloy will be roughly estimated based on the results of average corrosion rate in operation. It was also found that the kind and concentration of metal salt in the heating nitric acid solution gave a remarkable effect on the concentration of nitric acid vapor and the corrosion of Ti-5Ta in the hot nitric acid condensate. Most of the evaporators for reprocessing plants include metal ions in the heating nitric acid solution, so the metal salt effect is one of the corrosion factors to control the corrosion behavior of titanium alloy in condensate. The nitric acid concentration in the condensate increases by adding the metal salts in the heating nitric acid solution, in addition, the larger valence of metal ions was contributed to the increase of nitric acid concentration in the condensate. Consequently, the metal salts effect in the heating nitric acid solution accelerates the corrosion of Ti-5Ta in the nitric acid condensate.
Hamamoto, Shimpei; Shimazaki, Yosuke; Furusawa, Takayuki; Nemoto, Takahiro; Inoi, Hiroyuki
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 7 Pages, 2012/07
Takamatsu, Kuniyoshi; Sawa, Kazuhiro
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 10 Pages, 2012/07
A core dynamics analysis of the loss-of-forced-cooling test of the HTTR is performed. The relation between the reactivities (namely, the Doppler, moderator temperature, and xenon reactivities) affecting re-critical time and reactor peak power level and total reactivity is addressed. Furthermore, the analytical results for the reactor transient for a long time such as hundreds of hours are presented in this report. They can teach emergency operating procedures in case of loss of coolant accident (LOCA) of HTGR when the control rods are not inserted into the core and the reactor power control system does not operated. The analytical results will be utilized for the design and construction of the Kazakhstan High Temperature Reactor (KHTR) and the realization of commercial Very High Temperature Reactor (VHTR) systems.
Suzuki, Yoshio; Miyamura, Hiroko; Nakajima, Norihiro
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07
To estimate real behavior accurately by numerical simulations, it is indispensable to evaluate validity of simulation results because numerical simulations include various uncertainties such as "uncertainty due to randomness" and "uncertainty due to lack of knowledge". As one of approaches to evaluate validity of simulation results, we introduce "the degree of certainty" of simulations to real behavior. Here, to get a more accurate degree of certainty, we try to confirm the degree of influence about unevenness of uncertainty and to reduce uncertainty due to lack of knowledge. For this, we research and develop a validity evaluation system composed of three tools. We have applied them to our seismic simulation system which enables to execute the assembly structure analysis of an entire nuclear plant and confirmed that their functions are applicable to the simulation.
gasHata, Haruhi; Yokoyama, Kaoru; Sugitsue, Noritake
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 7 Pages, 2012/07
The uranium enrichment facilities, located at Ningyo-toge in Japan, are contaminated by uranium fluorides. There is the risk of exposing the HF gas when the equipments will be dismantled. Therefore, we performed the systematic chemical decontamination by using IF gas. This paper reports the actual results of the decontamination by using IF gas. The result shows that the decontamination factor is approximately 100 or more. In addition, we performed the simulation of the reactions with IF gas and uranium fluorides.
Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Tobita, Yoshiharu
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 11 Pages, 2012/07
The introduction of Fuel Assembly with Inner Duct Structure (FAIDUS) is being studied to prevent the formation of a large-scale molten fuel pool within a reactor core, which is one of factors leading to the severe power excursion during CDA of SFRs. In the current reference design for FAIDUS, the top end of the inner duct is open whereas the bottom end is closed. In order to clarify the fundamental mechanism for upward fuel discharge through the inner duct, JAEA conducted an out-of-pile experiment in which a high-density melt simulating the molten fuel was injected into a simulated inner duct. In this paper, the mechanism of upward discharge observed in this experiment is discussed in terms of the application to reactor conditions. It was suggested that the coolant pressure buildup could act as one of the driving force for the upward discharge under reactor conditions with higher melt-enthalpy-injection rate than the current experimental condition.
Ueno, Fumiyoshi; Shiraishi, Hironori; Inoue, Shun; Motooka, Takafumi; Kato, Chiaki; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 8 Pages, 2012/07
In PUREX process for spent fuel reprocessing plants, heating portions in the components are severely corroded in the boiling solution under heat transfer (HT) conditions. In this paper, authors have focused on the effects of surface temperature and heat flux on corrosion rates (CRs) of stainless steels in boiling nitric acid under HT conditions. Two types of cells for HT and immersion conditions were applied for corrosion tests. Test solution used was 33 mol/m
vanadium added to 3 kmol/m nitric acid solution, and was heated at boiling temperature under atmospheric pressure. Additionally, a boiling curve which was indicated the relation between heat flux and degree of superheating was investigated experimentally. Surface temperatures during corrosion tests were estimated from a boiling curve. The results showed that CR did not depend on heat flux, but depended on surface temperature. Arrhenius plots on CRs indicated that CR was accelerated by solution boiling against non-boiling.
Uchibori, Akihiro; Ohshima, Hiroyuki
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 10 Pages, 2012/07
In order to establish a safety evaluation method of a steam generator of sodium-cooled fast reactors, a computer program called SERAPHIM calculating compressible multicomponent multiphase flow with sodium-water chemical reaction under tube failure accident has been developed. In this study, a numerical model for liquid droplet entrainment from an interface of the gaseous jet and its transport was newly constructed to evaluate the environment of the liquid droplet impingement erosion. The applicability of the SERAPHIM program which incorporates the droplet entrainment / transport model was demonstrated through the analysis of vertical discharging of water vapor in the liquid sodium pool under the actual condition of the steam generator.
Nago, Kohei*; Koizumi, Yasuo*; Uchibori, Akihiro; Ohshima, Hiroyuki
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07
The experiment on a two dimensional air jet in a thin vessel filled with water was carried out to investigate the behavior of the jet interface and liquid droplet entrainment. The air jet in the water was recorded with a high speed video camera. The recorded photos showed that the filament-like ears and wisps were pulled out from the wavy water surface and the droplets were entrained. Droplet diameters and entrainment rate were obtained from the recorded photos. As the air velocity increased, the number of droplets increased lineally and the smaller droplets increased. The correlation for the droplet diameter distribution developed for the annular dispersed two-phase flow in a pipe predicted well the present experimental results. The correlations for the gas jet in the liquid pool underestimated the experimental results.
Kudo, Hideyuki*; Sugiyama, Kenichiro*; Narabayashi, Tadashi*; Ohshima, Hiroyuki; Kurihara, Akikazu
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07
For the sodium-water reaction accident, it is important to grasp the structure of gas jets submerged in liquid sodium and associated droplet size. In this study, we successfully obtained visualized images of inert gas jets injected into liquid sodium. Formation processes of liquid sodium droplets entrained into the gas jets and drop-size distributions are discussed.
Koizumi, Yasuo*; Ote, Naosuke*; Kamide, Hideki; Ohno, Shuji; Ito, Kei
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 5 Pages, 2012/07
A sodium-cooled fast breeder reactor is now at the developing stage in Japan. One concern for safety is cover gas entrainment into the sodium coolant. The gas entrainment rate into liquid by the vortex formed on the free surface was examined experimentally. In the present experiments, test fluid was changed from water in the previous experiments to 20 cSt silicone oil. The liquid level in the test vessel was 25 mm in the present experiments. Only the vortex-type gas-entrainment was observed as in the previous experiments since the liquid level was low. The flow state observed at the flow visualization section of the outlet pipe was only a semi-annular flow. The initiation of the gas entrainment was delayed in the case of silicone oil compared with the case of water. The increasing rate of the gas entrainment to the liquid velocity is milder in the case of silicone oil than in the case of water.