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Journal Articles

Mechanism of upward fuel discharge during core disruptive accident in sodium-cooled fast reactors

Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Tobita, Yoshiharu

Journal of Engineering for Gas Turbines and Power, 135(3), p.032901_1 - 032901_9, 2013/03

 Times Cited Count:3 Percentile:76.85(Engineering, Mechanical)

The introduction of Fuel Assembly with Inner Duct Structure (FAIDUS) is being considered 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 simulant experimental condition.

Journal Articles

Development of Al-alloy coating for advanced nuclear systems using lead alloys

Kurata, Yuji; Yokota, Hitoshi*; Suzuki, Tetsuya*

Journal of Engineering for Gas Turbines and Power, 134(6), p.062902_1 - 062902_7, 2012/06

 Times Cited Count:4 Percentile:70.68(Engineering, Mechanical)

Nuclear systems using lead alloys are one of the promising reactor concepts with improved safety. This paper focuses on development of Al-alloy coating for nuclear systems using liquid lead-bismuth eutectic (LBE). It is necessary to improve corrosion resistance of steels because of high corrosiveness of liquid LBE at high temperatures. An Al-alloy coating method using Al, Ti and Fe powders and laser beam heating has been developed. Main defects formed in an Al-powder-alloy coating process are surface defects and cracks. Conditions required to avoid these defects have been studied. According to results of the corrosion tests at 550$$^{circ}$$C in liquid LBE, the Al-alloy coating layers on 316SS prevent severe corrosion attack observed in 316SS without coating. The good corrosion resistance of the Al-alloy coating is based on the thin Al-oxide film regenerated in liquid LBE. It is estimated that the range of the adequate Al concentration in the coating layer is from 4 to 12 wt%.

Journal Articles

Conceptual structure design of high temperature isolation valve for high temperature gas cooled reactor

Takada, Shoji; Abe, Kenji*; Inagaki, Yoshiyuki

Journal of Engineering for Gas Turbines and Power, 133(11), p.114501_1 - 114501_3, 2011/11

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

The high temperature isolation valve (HTIV) is a key component to assure the safety of a high temperature gas cooled reactor connected with a hydrogen production system for protections of radioactive material release from the reactor to the hydrogen production system as well as of combustible gas ingress to the reactor during accidents. The conceptual structure design of an angle type HTIV was carried out to propose a draft overall structure based on the diameter of seat of 445 mm from fabrication experiences of valve makers. Numerical results showed that the thermal stress locally increased at the root of the seat which was connected with the valve box. The stress was lowered below the allowable limit 120 MPa by decreasing thickness of the connecting part and increasing the temperature of valve box to around 350 $$^{circ}$$C. Creep analysis was also carried out to estimate a creep-fatigue damage based on the temperature history of the normal operation and the depressurization accident.

Journal Articles

The Study on abrasive water jet for predicting the cutting performance and monitoring the cutting situation in the water

Nakamura, Yasuyuki; Sano, Kazuya; Morishita, Yoshitsugu; Maruyama, Shinichiro*; Tezuka, Shinichi*; Ogane, Daisuke*; Takashima, Yuji*

Journal of Engineering for Gas Turbines and Power, 133(6), p.064501_1 - 064501_3, 2011/06

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

Abrasive water jet (AWJ), is to shoot the abrasive mixed with high-pressure water to the material for cutting, can cut most materials like metals and concretes in water with long stand-off means the length from the cutting head to the material for cutting. On the other hand, AWJ is required to reduce an amount of the abrasive because it becomes the waste. It is also difficult to monitor the cutting condition by any visual methods like a TV camera in the water becoming cloudy by both used abrasive and cut metal grit. For solving these issues, some cutting tests were conducted and (1) It was possible to predict an optimal supply rate of abrasive by considering the conservation of momentum between the water jet and the abrasive. (2) It was also possible to judge whether the material could be cut successfully or not by detecting the change in the frequency characteristics of vibration or sound caused during the cutting process.

Journal Articles

Safety evaluation of the HTTR-IS nuclear hydrogen production system

Sato, Hiroyuki; Ohashi, Hirofumi; Tazawa, Yujiro; Sakaba, Nariaki; Tachibana, Yukio

Journal of Engineering for Gas Turbines and Power, 133(2), p.022902_1 - 022902_8, 2011/02

 Times Cited Count:5 Percentile:63.15(Engineering, Mechanical)

A practical safety evaluation method, which enables to design, construct and operate hydrogen production plants under conventional chemical plant standards, is proposed. An event identification for the HTTR-IS nuclear hydrogen production system is conducted in order to select abnormal events which would change the scenario and quantitative results of the evaluation items from the existing HTTR safety evaluation. In addition, a safety analysis is performed for the identified events. The results of safety analysis for the identified five Anticipated Operational Occurrences and three Accidents show that evaluation items do not exceed the acceptance criteria during the scenario. In addition, the increase of peak fuel temperature is small in the most severe case, and therefore the reactor core was not damaged and cooled sufficiently.

Journal Articles

Design and construction of IFMIF/EVEDA lithium test loop

Kondo, Hiroo; Furukawa, Tomohiro; Hirakawa, Yasushi; Ida, Mizuho; Matsushita, Izuru*; Horiike, Hiroshi*; Kanemura, Takuji; Sugiura, Hirokazu*; Yagi, Juro*; Suzuki, Akihiro*; et al.

Journal of Engineering for Gas Turbines and Power, 133(5), p.052910_1 - 052910_6, 2010/12

 Times Cited Count:7 Percentile:55.37(Engineering, Mechanical)

As a major Japanese activity for the IFMIF/EVEDA, EVEDA Li Test Loop (ELTL) to simulate hydraulic and impurity conditions of IFMIF is under design and preparation for fabrication. Feasibility of hydraulic stability of the liquid Li target and the purification systems of hot traps are major key issues to be validated. This paper presents the current status of the design and construction of the EVEDA Li Test Loop. Detail designs of the loop components such as the target assembly, tanks, an electro-magnetic pump and flow meter and a cold trap for purification system are described in addition to the flow diagnostics system and the hot traps.

Journal Articles

Chromatography column system with controlled flow and temperature for engineering scale application

Watanabe, So; Goto, Ichiro*; Sano, Yuichi; Koma, Yoshikazu

Journal of Engineering for Gas Turbines and Power, 132(10), p.102903_1 - 102903_7, 2010/10

 Times Cited Count:5 Percentile:63.78(Engineering, Mechanical)

Journal Articles

Experimental study on gas entrainment due to nonstationary vortex in a sodium cooled fast reactor; Comparison of onset conditions between sodium and water

Kimura, Nobuyuki; Ezure, Toshiki; Miyakoshi, Hiroyuki; Kamide, Hideki; Fukuda, Takeshi*

Journal of Engineering for Gas Turbines and Power, 132(10), p.102908_1 - 102908_6, 2010/10

 Times Cited Count:7 Percentile:56.11(Engineering, Mechanical)

In sodium-cooled fast reactor, a compact reactor vessel (R/V) with increased sodium flow velocity was designed to reduce the construction cost. One of the thermal hydraulic problems in this design is gas entrainment at the free surface in the R/V. In most of past studies, water experiments were performed to investigate the gas entrainment in the reactor. It is necessary to evaluate an influence of fluid physical property on the gas entrainment phenomena. In this study, sodium experiments were carried out to clarify the onset criteria of the gas entrainment due to a free surface vortex. Water experiments using a test section in which geometry is the same as that in the sodium tests were also performed. The gas entrainment in water slightly tended to take place in comparison with that in sodium under low velocity conditions. Overall onset condition map on lateral and downward flow velocities in the sodium and water experiments were in good agreement.

Journal Articles

Measurement and analysis for rewetting velocity under post-BT conditions during anticipated operational occurrence of BWR

Shibamoto, Yasuteru; Maruyama, Yu; Nakamura, Hideo

Journal of Engineering for Gas Turbines and Power, 132(10), p.102909_1 - 102909_8, 2010/10

 Times Cited Count:2 Percentile:79.18(Engineering, Mechanical)

A series of experiments was performed for rewetting phenomena on dried-out fuel rod surfaces under post-BT (Boiling Transition) conditions with high-pressure and high-water flow rate simulating anticipated operational occurrences of a BWR. An analytical model for rewetting velocity, defined by a propagation velocity of a quench front, has been developed on the basis of the experimental results. The rewetting for the post-BT condition is characterized by the faster propagation of the quench front than that for reflood phase conditions during a postulated large-break loss-of-coolant accident. In order to provide an explanation of this characteristic, the present analytical model took an effect of a precursory cooling into account by modifying the existing correlation by Sun-Dix-Tien which is based on a one-dimensional analysis in a flow direction during the reflood phase. The present model demonstrates that the precursory cooling can significantly increase the rewetting velocity by more than an order of magnitude. Applying the experimental correlation developed in the separately conducted experiment into the heat transfer coefficient in the present model at a wet and a dry region with precursory cooling, our data of the rewetting velocity as well as the wall temperature profiles for the variable flow rates are successfully predicted.

Journal Articles

Effect of experimental conditions on gas core length and downward velocity of free surface vortex in cylindrical vessel

Monji, Hideaki*; Shinozaki, Tatsuya*; Kamide, Hideki; Sakai, Takaaki

Journal of Engineering for Gas Turbines and Power, 132(1), p.012901_1 - 012901_8, 2010/01

 Times Cited Count:12 Percentile:41.9(Engineering, Mechanical)

This paper deals with characteristics of surface vortex in a cylindrical vessel. One of the characteristics is a gas core length which is important to estimate the onset condition of the gas entrainment but influenced easily by the experimental condition. In the experiment using water, the effects of the water temperature, water level and the surface tension on the gas core length were investigated. The onset condition of the gas entrainment is sometimes estimated by using the Burgers vortex model but the real flow in the vessel is different from the model. The velocity fields were measured by PIV and the velocity gradient of the downward flow was discussed. The proper flow conditions for the Burgers vortex model are a high water level and a high flow rate.

Journal Articles

Modeling pressure fluctuation with cross flow in a tight-lattice rod bundle

Zhang, W.; Yoshida, Hiroyuki; Takase, Kazuyuki

Journal of Engineering for Gas Turbines and Power, 131(2), p.022901_1 - 022901_6, 2009/03

 Times Cited Count:0 Percentile:100(Engineering, Mechanical)

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