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Journal Articles

Study of neutron-nuclear spin correlation term with a polarized Xe target

Sakai, Kenji; Oku, Takayuki; Okudaira, Takuya; Kai, Tetsuya; Harada, Masahide; Hiroi, Kosuke; Hayashida, Hirotoshi*; Kakurai, Kazuhisa*; Shimizu, Hirohiko*; Hirota, Katsuya*; et al.

JPS Conference Proceedings (Internet), 33, p.011116_1 - 011116_6, 2021/03

In neutron fundamental physics, study of correlation term $${bf s}cdot{bf I}$$ of a neutron spin $${bf s}$$ and a target nuclear spin $${bf I}$$ is important because $${bf s}cdot{bf I}$$ term interferes to parity non-conserving (PNC) and time reversal non-conserving terms. For this study, a xenon (Xe) is an interesting nucleus because it has been observed an enhancement of PNC effect around neutron resonance peaks, and polarizes up to $$ sim 10^{-1}$$ by using a spin exchange optical pumping (SEOP) method. We would plan to develop a polarized Xe gas target with a compact in-situ SEOP system, and to study $${bf s}cdot{bf I}$$ term by utilizing epithermal neutron beams supplied from a high intense pulsed spallation neutron source. As the first step, we attempted to measure neutron polarizing ability caused by $${bf s}cdot{bf I}$$ term at a 9.6 eV s-wave resonance peak of $$^{129}$$Xe at BL10 in MLF, by detecting change $$Delta R$$ of ratio between neutron transmissions with the polarized and unpolarized Xe target. After demonstrating that our apparatus could detect small change ($$Delta R_{rm DB} , {approx},10^{-2}$$) of neutron transmissions caused by Doppler broadening effect, a signified value of $$Delta R$$ has been obtained as preliminary results. For analyzing the obtained $$Delta R$$ in detail, we are improving our nuclear magnetic resonance and electron paramagnetic resonance systems for evaluating Xe polarization independently of neutron beams.

Journal Articles

Prediction of thermodynamic data for radium suitable for thermodynamic database for radioactive waste management using an electrostatic model and correlation with ionic radii among alkaline earth metals

Kitamura, Akira; Yoshida, Yasushi*

Journal of Radioanalytical and Nuclear Chemistry, 327(2), p.839 - 845, 2021/02

 Times Cited Count:0 Percentile:100(Chemistry, Analytical)

Thermodynamic data for radium for radioactive waste management have been predicted using an electrostatic model and correlation with the ionic radii of the alkaline earth metals. Estimation of the standard Gibbs free energy of formation and standard molar entropy of aqueous radium species and compounds has been based on such approaches as extrapolation of the thermodynamic properties of strontium and barium, and use of a model of ion pair formation. The predicted thermodynamic data for radium have been compared with previously reported values.

Journal Articles

Axial flow characteristics of bubbly flow in a vertical large-diameter square duct

Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo

Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09

An experimental study on the upward bubbly air-water flows in a vertical large-diameter square duct have been performed by using four-sensor probes. The four-sensor probe were applied in the local measurements at 3 axial positions along the flow direction to obtain interfacial area concentration, 3-D bubble velocity vector and bubble diameter. The obtained void fraction, interfacial area concentration, 3-D bubble velocity vector and bubble diameter provided valuable insight into the flow structure and will serve as a valuable database to develop the mechanistic models for interfacial area transport equation sources and sinks.

JAEA Reports

Application of probability generating function to the essentials of nondestructive nuclear materials assay system using neutron correlation

Hosoma, Takashi

JAEA-Research 2016-019, 53 Pages, 2017/01

JAEA-Research-2016-019.pdf:5.71MB

Application of probability generating function for nondestructive nuclear materials assay system was studied. First, high-order neutron correlations were derived algebraically up to septuplet and basic characteristics of the correlations were investigated. It was found that higher-order correlation increases rapidly in response to the increase of leakage multiplication, crosses and leaves lower-order correlations behind, when leakage multiplication is $$>$$ 1.3 that depends on detector efficiency and counter setting. Next, fission rates and doubles count rates by fast neutron and by thermal neutron in their coexisting system were derived algebraically. It was found that the number of induced fissions per unit time by fast neutron and by thermal neutron, the number of induced fissions ($$<$$ 1) by one source neutron, and individual doubles count rates were possible to be estimated from Rossi-alpha combined distribution and measured ratio of each area obtained by differential die-away self-interrogation and conventional assay data.

Journal Articles

An Empirical correlation to predict the distance for fragmentation of simulated Molten-Core materials discharged into a sodium pool

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

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 8 Pages, 2016/10

In order to evaluate the distance for fragmentation of molten core material discharged into the lower sodium plenum during core disruptive accidents in sodium-cooled fast reactors, experiments with simulated molten materials and coolants (water, sodium) was carried out, where an empirical correlation of the distance for fragmentation was developed. The empirical correlation developed by this study showed a good agreement with the measurement results obtained by the present experiments. It was found that in order to well-predict the distance for fragmentation in sodium, thermal phenomena, such as sodium boiling and resultant vapor expansion, needed to be considered.

Journal Articles

Gas-liquid bubbly flow structure in a vertical large-diameter square duct

Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo

Progress in Nuclear Energy, 89, p.140 - 158, 2016/05

 Times Cited Count:11 Percentile:15.53(Nuclear Science & Technology)

An experimental study was performed on the local structure of upward air-water two-phase flow in a vertical large diameter square duct by using a four-sensor probe. The four-sensor probe method classifying spherical and non-spherical bubbles was applied as a key measurement way to obtain local parameters such as 3-D bubble velocity vector, bubble diameter and interfacial area concentration. Both the local void fraction and interfacial area concentration indicated radial core-peak and wall-peak distributions at low and high liquid flow rates respectively. The 2 components of the bubble velocity vector in the cross-section revealed that there exists a rotating secondary flow in the octant symmetric triangular area and the magnitude of the rotating secondary flow increases with the liquid flow rate. Some of constitutive correlations of drift-flux model and interfacial area concentration are reviewed to study their predictabilities against the present data.

Journal Articles

Critical power prediction for tight lattice rod bundles

Liu, W.; Onuki, Akira; Tamai, Hidesada; Akimoto, Hajime

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 5 Pages, 2005/10

In this research, the newest version of critical power correlation for tight-lattice rod bundles is proposed by using 7-rod and 37-rod bundle data derived in Japan Atomic Energy Research Institute (JAERI). For comparatively high mass velocity region, the correlation is written in local critical heat flux - critical quality type. For low mass velocity region, it is written in critical quality - annular flow length type. The correlation is verified by JAERI data and Bettis Atomic Power Laboratory data. It is confirmed the correlation is able to give good prediction for the effects of mass velocity, inlet temperature, pressure and heated equivalent diameter on critical power. The correlation is further implemented into TRAC code to analyze flow decrease and power increase transients. It is confirmed transient BT can be predicted within the accuracy of the implemented critical power correlation.

JAEA Reports

Numerical analysis of interfacial growth and deformation in horizontal stratified two-phase flow by lattice Boltzmann method

Ebihara, Kenichi

JAERI-Research 2005-004, 121 Pages, 2005/03

JAERI-Research-2005-004.pdf:19.79MB

This report is the JAERI's report version of the doctor thesis by the author. In this report, first, the validity and usefulness of the application of the two-phase fluid model of the lattice-gas method and the lattice Boltzmann method(LBM) are examined. On the basis of the examination, next, the horizontal stratified two-phase flow that is the fundamental and important flow is simulated by the HCZ model which is one of the two-phase fluid model of the LBM. It is seen that the interfacial growth of the HCZ model satisfies the Kelvin-Helmholtz instability theory and reproduces the theoretical two-phase flow regime map of Taitel and Dukler(T-D map). It is found that more superficial flow velocity of the rare phase is necessary in the channel with the narrow width. The HCZ model can also simulate the droplet generation accompanying more complex interfacial phenomena and reproduce the experimental correlation of Ishii and Grolmes in the range of the distribution of the experimental data.

Journal Articles

Critical power correlation for tight-lattice rod bundles

Liu, W.; Kureta, Masatoshi; Onuki, Akira; Akimoto, Hajime

Journal of Nuclear Science and Technology, 42(1), p.40 - 49, 2005/01

 Times Cited Count:7 Percentile:52.3(Nuclear Science & Technology)

In this research, critical power correlation for tight-lattice rod bundles is newly proposed using 7-rod axially uniform-heated data, 7-rod and 37-rod axially double-humped-heated data at Japan Atomic Energy Research Institute (JAERI). For low mass velocity region ($$<$$ 300 kg/m$$^{2}$$s), the correlation is written in critical quality - annular flow length type. For high mass velocity region ($$>$$ 300 kg/m$$^{2}$$s), it is written in local critical heat flux - critical quality type. The standard deviation of ECPR (Experimental Critical Power Ratio) to the whole JAERI data (694 data points) is 6%. The correlation is verified by Bettis Atomic Power Laboratory data (177 points, standard deviation: 7.7%). The correlation is confirmed being able to give good prediction for the effects of mass velocity, inlet temperature, pressure and heated equivalent diameter on critical power. The applicable range of the correlation is: gap between rods from 1.0 to 2.29 mm, heated length from 1.26 to 1.8 m, mass velocity from 150 to 2000 kg/m$$^{2}$$s and pressure from 2 to 11 MPa.

Journal Articles

$$^{1}S_{0}$$ proton superfluidity in neutron star matter; Impact of bulk properties

Tanigawa, Tomonori; Matsuzaki, Masayuki*; Chiba, Satoshi

Physical Review C, 70(6), p.065801_1 - 065801_7, 2004/12

 Times Cited Count:9 Percentile:47.06(Physics, Nuclear)

We study the $$^{1}S_{0}$$ proton pairing gap in neutron star matterputting emphasis on influence of the Dirac effective mass and theproton fraction on the gap within the relativistic Hartree-Bogoliubovmodel. The gap equation is solved using the Bonn-B potential as aparticle-particle channel interaction. It is found that the maximalpairing gap $$Delta_mathrm{max}$$ is 1-2MeV, which has a strongcorrelation with the Dirac effective mass. Hence we suggest that itserves as a guide to narrow down parameter sets of the relativisticeffective field theory. Furthermore, the more slowly protons increasewith density, the lower the peak of the gap and the wider thesuperfluid range become.

Journal Articles

Study on interfacial growth and deformation of horizontal stratified two-phase flow by lattice Boltzmann method

Ebihara, Kenichi

Tsukuba Daigaku Daigakuin Shisutemu Joho Kogaku Kenkyuka Hakase Gakui Rombun, 134 Pages, 2004/09

In this thesis, first the liquid-gas models of the lattice method are examined by applying them to two-phase flow simulations. Next the liquid-gas model(the HCZ model) of the lattice Boltzmann method is applied to the three-dimensional simulation of the horizontal stratified two-phase flow. The following results are obtained. (1)The two- and three- dimensional interface simulated by the HCZ model satisfies the Kelvin-Helmholtz instability theory. (2)In the simulation of the interfacial growth in the rectangular channel, it is found that the relation between the interfacial growth and the flow state is in agreement with the flow regime map proposed theoretically by Taitel and Dukler. (3)It is also found that the three dimensionality becomes remarkable and the interfacial growth needs more flow rate of the rare phase than that of the theoretical flow regime map when the channel width is narrower. (4)In the droplet creation simulation, it is found that the relation between the droplet creation and the flow state simulates the experimental correlation proposed by Ishii and Grolmes.

Journal Articles

The Lattice Boltzmann simulation of the droplet creation in the horizontal stratified two-phase flow

Ebihara, Kenichi; Watanabe, Tadashi

Nagare, 23(4), p.253 - 261, 2004/08

The lattice Boltzmann method for one-component two-phase fluid is applied to the simulation of the droplet creation in the horizontal stratified two-phase flow. It is observed in several flow states that the droplet tears from the interface wave. The dimensionless numbers that characterize the flow state are also measured during the simulations. After checking the influence of the lattice length and width to the simulation result, the relation between the droplet creation and the measured dimensionless numbers is compared with the inception criteria of the droplet creation that was proposed on the basis of experimental data by Ishii and Grolmes. It was found that the simulation results are included in the devitation of experimental data from the correlation of Ishii-Grolmes.

Journal Articles

Theory of superconductivity in strongly correlated electron systems

Yanase, Yoichi*; Jujo, Takanobu*; Nomura, Takuji; Ikeda, Hiroaki*; Hotta, Takashi; Yamada, Kosaku*

Physics Reports; A Review Section of Physics Letters, 387(1-4), 149 Pages, 2003/11

In this article we review essential natures of superconductivity in strongly correlated electron systems from a universal point of view. Here we consider materials such as high-$$T_{rm c}$$ cuprates, BEDT-TTF organic superconductors, ruthenate Sr$$_2$$RuO$$_4$$, and heavy fermion superconductors. After the review of experimental results, we explain the formalism to discuss superconducting properties of strongly correlated electron systems based on the Dyson-Gor'kov equations. Then, we introduce theoretical retults on cuprates, organics, ruthenate, and heavy fermion superconductors in this order.

Journal Articles

Classification of criticality calculations with correlation coefficient method and its application to OECD/NEA burnup credit benchmarks phase III-A and II-A

Okuno, Hiroshi

Journal of Nuclear Science and Technology, 40(7), p.544 - 551, 2003/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

A method for classifying benchmark results of criticality calculations according to similarity was proposed in this paper. After formulation of the method utilizing correlation coefficients, it was applied to burnup credit criticality benchmarks Phase III-A and II-A, which were conducted by the Expert Group on Burnup Credit Criticality Safety under auspices of the OECD/NEA. Phase III-A benchmark was a series of criticality calculations for irradiated BWR fuel assemblies, whereas Phase II-A benchmark was a suite of criticality calculations for irradiated PWR fuel pins. These benchmark problems and their results were summarized. The correlation coefficients were calculated and sets of benchmark results were classified according to the criterion that the correlation coefficients were no less than 0.15 for Phase III-A and 0.10 for Phase II-A benchmarks. When a couple of results were in a same group, one result was found predictable from the other. An example was shown for each of the Benchmarks. The evaluated nuclear data seemed the main factor of errors.

Journal Articles

Possibility of $$LambdaLambda$$ pairing and its dependence on background density in a relativistic Hartree-Bogoliubov model

Tanigawa, Tomonori; Matsuzaki, Masayuki*; Chiba, Satoshi

Physical Review C, 68(1), p.015801_1 - 015801_8, 2003/07

 Times Cited Count:14 Percentile:33.3(Physics, Nuclear)

We calculate a $$LambdaLambda$$ pairing gap in binary mixed matter of nucleons and $$Lambda$$ hyperons within the relativistic Hartree-Bogoliubov model since a recent experiment suggests a weaker $$LambdaLambda$$ attraction than before, which has a significant impact on properties of neutron stars in various aspects. Lambda hyperons to be paired up are immersed in background nucleons in normal state. A phenomenological $$LambdaLambda$$ interaction, which is derived relativistically from the Lagrangian of the system, is adopted to the gap equation. It is found that at background density $$rho_{N}=2.5rho_{0}$$ the $$LambdaLambda$$ pairing gap is very small, and that denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density.

Journal Articles

Atmospheric deposition of $$^{7}$$Be, $$^{40}$$K, $$^{137}$$Cs and $$^{210}$$Pb during 1993-2001 at Tokai-mura, Japan

Ueno, Takashi; Nagao, Seiya; Yamazawa, Hiromi

Journal of Radioanalytical and Nuclear Chemistry, 255(2), p.335 - 339, 2003/02

 Times Cited Count:16 Percentile:26.36(Chemistry, Analytical)

To evaluate the migration of radionuclides to the ground surface, deposition was collected from 1993 to 2001 with basin set up at Japan Atomic Energy Research Institute at Tokai-mura. Monthly basin samples were evaporated to dryness to obtain residual samples.These samples were measured by a well type Ge detector for natural and fallout radionuclide. These monthly depositions showed a clear seasonal variation with peaks in the early spring from February to April, and also in May in some years. The depositions of $$^{40}$$K and $$^{137}$$Cs have good correlation with the dry weight of deposited material, the depositions of $$^{7}$$Be and $$^{210}$$Pb showed much lower correlation coefficients. This difference in the correlation coefficient between these two groups of radionuclides can be attributed to the difference in the originating processes. These features in the concentration are thought to be caused by the difference in mechanism and location of origination, which would result in difference in the contributing particle size, and hence by the difference in the transport and deposition processes.

JAEA Reports

Abstracts of the Workshop on Orbital Ordering and Fluctuations in d- and f-electron Systems; March 4-6, 2002, ASRC, JAERI, Tokai, Japan

Ueda, Kazuo; Hotta, Takashi

JAERI-Review 2002-037, 31 Pages, 2002/12

JAERI-Review-2002-037.pdf:2.7MB

Strongly correlated f- and d-electron systems including heavy Fermion systems and transition metal oxides are important source of exciting new phenomena in condensed matter physics. Recently it has been recognized in more profound way that the orbital degeneracy of the f- and d-electrons plays very important role underlying those exotic phenomena. The idea of the present workshop is to bring active researchers in the field together and to exchange ideas in informal atmosphere. In the workshop many interesting results were presented and stimulating discussions were made as clearly seen by the present report.

Journal Articles

Nonlocal transport phenomena and various structure formations in plasmas; Introduction

Kishimoto, Yasuaki

Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.857 - 860, 2002/09

In order to understand the various phenomena related to the nonlocal transport and structure formation in the plasma, we reviw the topics in the field of (1)laser implosion plasma, (2)space plasma, and (3) magnetic fusion plasma, as a spatial series.

JAEA Reports

User's manual of SECOM2: A Computer code for seismic system reliability analysis

Uchiyama, Tomoaki; Oikawa, Tetsukuni; Kondo, Masaaki; Watanabe, Yuichi*; Tamura, Kazuo*

JAERI-Data/Code 2002-011, 205 Pages, 2002/03

JAERI-Data-Code-2002-011.pdf:8.52MB

This report is a user's manual of seismic system reliability analysis code SECOM2 developed at the JAERI for system reliability analysis, which is one of the tasks of seismic probabilistic safety assessment (PSA) of nuclear power plants (NPPs). The SECOM2 code has many functions such as calculation of component and system failure probabilities for given seismic motion levels at the site of an NPP based on the response factor method, calculation of accident sequence frequencies and the core damage frequency (CDF), importance analysis using various indicators, uncertainty analysis, and calculation of the CDF taking into account the effect of the correlations of responses and capacities of components. These analyses require the fault tree (FT) representing the occurrence condition of the system failures and core damage, information about responses and capacities of the components which compose the FT, and seismic hazard curve for the NPP site as input. This report presents calculation method used in the SECOM2 code and how to use those functions in the SECOM2 code.

Journal Articles

Prediction of orbital ordering in single-layered ruthenates

Hotta, Takashi; Dagotto, E.*

Physical Review Letters, 88(1), p.017201_1 - 017201_4, 2002/01

 Times Cited Count:71 Percentile:10.31(Physics, Multidisciplinary)

The key role of the orbital degree of freedom to understand the magnetic properties of layered ruthenates is here discussed. In the G-type antiferromagnetic (AFM) phase of Ca$$_2$$RuO$$_4$$, recent X-ray experiments reported the presence of 0.5 hole per site in the $$d_{rm xy}$$ orbital, while the $$d_{rm yz}$$ and $$d_{rm zx}$$ orbitals contain 1.5 holes. This unexpected $$t_{rm 2g}$$ hole distribution is explained by a novel state with orbital ordering (OO), stabilized by a combination of Coulomb interactions and lattice distortions. In addition, the rich phase diagram presented here suggests the possibility of large magnetoresistance effects, and predicts a new ferromagnetic OO phase in ruthenates.

74 (Records 1-20 displayed on this page)