Journal of Nuclear Science and Technology
Online ISSN : 1881-1248
Print ISSN : 0022-3131
33 巻, 12 号
選択された号の論文の12件中1~12を表示しています
  • In Cheol LIM, Hee Cheon NO
    1996 年 33 巻 12 号 p. 903-914
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    A model is developed to describe the transition from annular flow to intermittent flow in a vertical two- phase flow system. Since the instability of the disturbance wave, which is a dominant wave shape at the boundary between annular flow and intermittent flow, is considered as a governing mechanism, this instability described by the concept of hyperbolicity breaking in the characteristic equation is included in the model. The developed model is validated by comparing its predictions of gas superficial velocity for the transition with experimental data available in the literature, and comparing those with the predictions of the other correlations. The comparison results show that the model gives better predictions for the transition condition than existing correlations, and the effects of fluid properties, geometry and liquid flow rate on the transition are well considered by the developed model. The average of prediction errors is 3% for the present model. The standard deviation of the prediction errors of the model reaches 28%, which is the smallest among the models compared here.
  • Masanori ARITOMI, Shirong ZHOU, Makoto NAKAJIMA, Yasushi TAKEDA, Michi ...
    1996 年 33 巻 12 号 p. 915-923
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    The authors have been developing a measurement system for bubbly flow in order to clarify its multi- dimensional flow characteristics and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system combining an ultrasonic velocity profile monitor with a video data processing unit is proposed, which can measure simultaneously velocity profiles in both gas and liquid phases, a void fraction profile for bubbly flow in a channel, and an average bubble diameter and void fraction. Furthermore, the proposed measurement system is applied to measure flow characteristics of a bubbly countercurrent flow in a vertical rectangular channel to verify its capability.
  • Takehiko NAKAMURA, Hideo SASAJIMA, Toyoshi FUKETA, Kiyomi ISHIJIMA
    1996 年 33 巻 12 号 p. 924-935
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Behavior of irradiated fuel rods under power burst conditions by accidental reactivity insertion in light water reactors (LWRs) has been studied in the Nuclear Safety Research Reactor (NSRR). In the experiments, cladding hoop deformation, which reached up to about 10%, was much larger than that of the fresh rods. The current LWR fuel behavior analysis codes, which only take account of the thermal expansion of the fuel pellets for the deformation calculation, under-predicted the plastic deformation of the cladding to be less than about 1%. Fission gas release during the pulse irradiation tests reached as high as 22% in the NSRR irradiated fuel tests. In order to describe these test results, a model of grain boundary fission gases to cause the cladding deformation has been developed and installed in a fuel behavior simulation code, FRAP-T6. In the model, the over-pressurized gases by the pulse irradiation cause grain boundary separation and stress the cladding during the tests. The model assumes that the gases remain in the fuel during the early part of pulse irradiation and are released to the open volume in the rod after the cladding deformation. The model, in combination with a fuel thermal expansion model, GAPCON, which was validated through fresh fuel tests, reproduces the NSRR test results reasonably well.
  • Hirokazu OKADA, Shigeharu UKAI, Masaki INOUE
    1996 年 33 巻 12 号 p. 936-943
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Oxide Dispersion Strengthened (ODS) ferritic steel is the promising candidate alloy for long-life core ma- terials of fast reactor. A series of experiments, such as tensile tests, creep rupture tests, texture measurements and microstructure observations, are performed for the fabricated sheets of ODS ferritic steel with simulat- ing type of morphology and also for the cladding tube in order to clarify the origin of the peculiar strength anisotropy of the cladding tube: degraded creep rupture strength in hoop direction. From these experiments, effects of grain morphology and texture on deformation of ODS ferritic steels are evaluated. The sheets and the cladding tube have strong texture of {001}<110> and {111}<110>, respectively. In longitudinal and transverse directions of the sheets, strength level is significantly different from each other, but crystallographic orientation is almost equivalent. From that finding, it is considered that strength anisotropy of the cladding tubes is not attributed to the texture. From the results of micro structure analysis, it is concluded that origin of the degraded creep rupture strength in transverse hoop direction of the cladding tube comes from the grain boundary sliding at the large tilt angles.
  • Yuji HATANO, Kanetsugu ISOBE, Ryuji HITAKA, Masayasu SUGISAKI
    1996 年 33 巻 12 号 p. 944-949
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    The hydrogen uptake behavior of two types of Zircaloy-2 specimens containing either fine intermetallic precipitates or coarse ones was studied at 623-723K in the pre-transition period of oxidation to clarify the role of the precipitates in the hydrogen transport through the oxide film. In the former case, the amount of hydrogen taken up was small and did not show the oxidation temperature dependence. In the latter case, the amount of hydrogen taken up was large and dependent markedly upon the oxidation temperature; it increased with decreasing oxidation temperature. These results were successfully explained with the model that the intermetallic precipitates remaining in a metallic state in the oxide film act as the fast transport route of hydrogen.
  • Haruo SATO, Mikazu YUI, Hideki YOSHIKAWA
    1996 年 33 巻 12 号 p. 950-955
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    The ionic diffusion coefficients for Cs+ Pb2+, Sm3+ Ni2+, SeO42- and TcO4- in free water (Do) were determined at room temperature by measuring conductivity. The Do values were derived based on the Nernst- Einstein equation. The limiting ionic equivalent conductivities (λo) for Cs+ Pb2+, Sm3+ Ni2+ and SeO42- were derived based on Kolrausch's square-root law and that for TcO4- was derived from the relation between the concentration of TcO4- in the solution and the λ because of its weak electrolyte. The Do values were in a range of 1.4 to 2.2×10-9m2/s. The Do values for Cs+ Pb2+, Sm3+ Ni2+ and SeO42- and those found in the literature showed good agreement. The Do for TcO4-, which was previously unknown, was determined to be 1.95×10-9m2/s, which is similar to that for analogous chemical species. The variation in Do has been expected to be approximately one order of magnitude at constant temperature and all Do values determined in this work were in this range. The variation in activation energy for diffusion for some important ions was less than a factor of two and it is concluded that the temperature dependence of Do is approximately the same.
  • Ryota OMORI, Kenji SAWADA, Tamiki KOBAYASHI, Atsuyuki SUZUKI
    1996 年 33 巻 12 号 p. 956-963
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Optical trappings of ThO2 and UO2 particles have been first demonstrated in water using the radiation pressure of a TEM00-mode He-Ne laser beam of λ=633nm. It was observed that a ThO2 particle was success- fully trapped three-dimensionally in the focus region and transferred by moving the focus. On the other hand, for a UO2 particle of which a refractive index and an extinction coefficient are relatively large in the visible region, only two-dimensional trapping was observed when the beam focus was located near the bottom of the particle. One of the main difficulties in the optical trapping of nuclear fuel particles is attributed to their relatively large absorption coefficients in the visible region. Computational studies on three-dimensional op- tical trapping performances of absorbing particles were, therefore, perfomed with a simulation code based on geometrical optics. The present calculation can well predict the experimental results on the optical trapping characteristics for ThO2 and UO2 particles.
  • M. BOTTONI, S. AHUJA
    1996 年 33 巻 12 号 p. 964-972
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Two-phase flow of coolant is described in subassemblies of liquid metal fast breeder reactors by a one- dimensional two-phase multibubble slug ejection model. Vapor flow of sodium between the slugs is modeled as annular flow with a moving liquid film of variable thickness wetting structural surfaces. The two-phase pressure drop multiplier concept introduced by Lockhart-Martinelli is used in the frame of the slug ejection model with an algorithm that simultaneously computes interfacial friction coefficient and liquid film axial velocity distribution. The implicit continuous Eulerian (ICE) technique developed by Harlow and Amsden for computing pressure distribution in a continuum medium is applied in heterogeneous two-phase flow to the governing equations for the vapor phase. This solution method is more stable than the numerical solution by finite differences of the vapor momentum equation.
  • Reducing Reactions and Alloy Formation by Platinum Group Elements, Molybdenum and Corrosion Products Taking Place in Simulated HLLW
    Masayosi UNO, Youji KADOTANI, Hajime KINOSHITA, Chie MIYAKE, Misato HO ...
    1996 年 33 巻 12 号 p. 973-980
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    An experimental study made on the reducing reactions and the formation of alloys taking place in oxide mixtures representing high-level liquid waste (HLLW) generated by the PUREX process, and in particular, on the effect brought on the metal melting temperature by the presence of corrosion products mainly Fe, Cr, Ni deriving from the vessels used in the process. It proved that heat treatment at 1, 873K melted the metal phases produced from all the starting mixtures taken up. The metal phases obtained from starting mixtures of corrosion products or their oxides proved to contain alloys of Cr-Fe-Ni, Fe-Ni and Cr-Ni, and in addition Ru-Fe alloy and Mo, Pd metals when the starting mixture further included platinum metals and molybdenum oxides, which also are found in the HLLW from PUREX process. The same six alloys and metals cited above were formed in the metal phases obtained from simulated calcined HLLW used as starting mixture. The melting of Ru and Mo at 1, 873K far below their melting points was attributed to the dissolution of Fe into Ru and of Fe or Ni into Mo.
  • Yasunori IWAI, Toshihiko YAMANISHI, Kenji OKUNO, Nobuhisa YOKOGAWA, Hi ...
    1996 年 33 巻 12 号 p. 981-992
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Two types of water detritiation systems have been designed for fusion reactors of ITER scale. One of the systems is a combination of WD (Water Distillation) and VPCE(vapor phase catalytic exchange) columns. The other is a combination of a WD column and a CECE(combined electrolysis catalytic exchange) column. Three water distillation columns are needed for the former system. The total height of the three columns is 106 m. The height of the water distillation and CECE columns for the latter system are 20 and 24m, respectively. These large water distillation columns result in the larger tritium inventory of the former system than for the latter system. However, there have been the results for the operation of the actual scale of the water distillation and VPCE columns. No demonstration test has been carried out for the CECE column. From these reasons, the WD+VPCE system should be the first candidate for the fusion reactor. The WD+CECE system is superior to the WD+VPCE system for the flexibility in design as well as the tritium inventory. It is desired to demonstrate the CECE column to develop the water detritiation system best suited to the fusion reactors.
  • Kenji KOTOH, Kazuhiko KUDO
    1996 年 33 巻 12 号 p. 993-1002
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
    Two types of multi-column adsorption system are proposed as the system for removal of tritiated moisture from tritium process gases or/and handling room atmospheres. The types are of recycle use of adsorption columns, and are composed of twin or triplet columns and one condenser which is used for collecting the adsorbed moisture from columns in desorption process. The systems utilize the dry gas from a working column as the purge gas for regenerating a saturated column and appropriate an active column for recovery of the tritiated moisture passing through the condenser. Each column hence needs the additional amount of adsorbent for collecting the moisture from the condenser. In the modeling and design of an adsorption column, it is primary to estimate the necessary amount of a candidate adsorbent for its packed-bed. The performance of the proposed systems is examined here by analyzing the dependence of the necessary amount of adsorbent for their columns on process operational conditions and adsorbent moisture-adsorption characteristics. The result shows that the necessary amount is sensitive to the types of adsorption isotherm, and suggests that these systems should employ adsorbents which exhibit the Langmuir-type isotherms.
  • Shekhar KUMAR, S.B. KOGANTI
    1996 年 33 巻 12 号 p. 1003-1005
    発行日: 1996/12/25
    公開日: 2008/04/18
    ジャーナル フリー
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