Toward mechanistic evaluation of critical heat flux in nuclear reactors, 2; Recent studies and future challenges toward mechanistic and reliable CHF evaluation

Okawa, Tomio*; Mori, Shoji*; Liu, W.*; Ose, Yasuo*; Yoshida, Hiroyuki; Ono, Ayako

Nihon Genshiryoku Gakkai-Shi ATOMO, 63(12), p.820 - 824, 2021/12

https://doi.org/10.3327/jaesjb.63.12_820

The evaluation method of the critical heat flux based on the mechanism is needed for the efficient design and development of fuel in reactors and the appropriate safety evaluation. In this paper, the current researches relating to the mechanism of the critical heat flux are reviewed, and the issue to be considered in the future are discussed.

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe

Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Nakamura, Ai*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

https://doi.org/10.7566/JPSJ.90.073707

Impedance spectra analysis of thermoresponsive poly(acryloyl--proline methyl ester) gel membrane in LiCl solution

Chen, J.; Asano, Masaharu; Tsubokawa, Norio*; Maekawa, Yasunari; Yamaki, Tetsuya; Yoshida, Masaru

Journal of Polymer Science, Part B; Polymer Physics, 43(20), p.2843 - 2851, 2005/10

https://doi.org/10.1002/polb.20570

Impedance spectra analysis of a thermo-responsive poly(acryloyl--proline methyl ester) (poly(A-ProOMe)) hydrogel membranes in an aqueous solution of LiCl was carried out using a simple equivalent model. The hydrogel membrane was synthesized by -radiation-induced polymerization and crosslinking of A-ProOMe monomer aqueous solution in a glass-cast. By means of the impedance spectra analysis, a novel method for the calculation of the ionic conductivity of the hydrogel membranes in LiCl solution was proposed. The calculated ionic conductivity was in agreement well with the determined value. In addition, effects of temperature and LiCl concentration on the impedance spectra and ionic conductivity of the gel membrane were analysized. Results indicated that the impedance spectra analysis is a very useful tool for evaluating the electric properties of gel membranes in an electrolyte solution. The poly(A-ProOMe) gel membrane in 1.0 M LiCl solution showed a high ionic conductivity of about 0.2 S/cm at 14C. The temperature-dependence of the ionic conductivity was a complex nonlinear form due to the volume phase transition of the thermo-responsive poly(A-ProOMe) gel membrane, and the volume phase transition temperature appeared to be decreased with the increase in the LiCl concentration.

Structural studies on liquids and glasses under high pressure and high temperature

Katayama, Yoshinori; Inamura, Yasuhiro*

Nuclear Instruments and Methods in Physics Research B, 238(1-4), p.154 - 159, 2005/08

https://doi.org/10.1016/j.nimb.2005.06.038

It is well know that many substances have different structures in the crystalline state and they exhibit first-order structural phase transitions by a change in pressure. On the other hand, pressure-induced structural changes in the liquid and glassy states were supposed to be monotonous. The recent development of synchrotron radiation sources enables us to perform structural studies on liquids and glasses under high pressure and high temperature conditions. These studies revealed that the changes in the liquid and glassy states are not necessarily monotonous. We will present recent results on liquid phosphorus and silica glass.

Sedimentation of substitutional solute atoms in In-Pb system alloy under strong gravitational field; Experiments and simulations

Ono, Masao; Kinoshita, Takahiro*; Ueno, Hideto*; Huang, X.*; Osakabe, Toyotaka; Mashimo, Tsutomu

Materials Transactions, 46(2), p.219 - 224, 2005/02

https://doi.org/10.2320/matertrans.46.219

Ultracentrifuge experiments were performed on the In-Pb system to study the sedimentation of atoms and phase equilibrium. After the experiments, the graded structures were obtained. Pb-rich phase (f.c.c) and In-rich phase (tetragonal) appeared at the strong- and weak-gravitational field sides of the sample, respectively, from starting state of -phase. And, the continuous changes in lattice parameters were observed in each phase. These observation results showed that the graded structure was continuous in atomic scale, and was formed by the sedimentation of atoms. Composition profiles of the centrifuged samples for 31.3 h, 60 h and 150 h showed that the composition change reached the steady state within 60 hours. The diffusion coefficient for sedimentation was estimated to be about 8 times larger than that for usual diffusion by the simulation. The result indicated that the diffusion mechanism of the sedimentation was different from the conventional ones.

Phase transitions of the mean-field Potts glass model in a field

Yokota, Terufumi

Physical Review B, 70(17), p.174422_1 - 174422_14, 2004/11

https://doi.org/10.1103/PhysRevB.70.174422

Phase transitions in the infinite-range p-state Potts glass model is studied in the presence of a field. Phase transition line into the transverse ordered phase is a straight line in a field-temperature phase diagram for small field and small effective ferromagnetic interaction. This is in contrast with the Gabay-Toulouse line for the vector spin-glass model. Replica symmetry breaking pattern is discussed near the phase transition line. Replica symmetry for the longitudinal order parameter is weakly broken at higher temperature than the transition line to the transverse ordered phase for p3.2. For p4.6, the transition to the transverse ordered phase reveals discontinuity in the order parameter just as the p4 case without a field.

Minutes of the IFMIF technical meeting; December 4-5, 2003, Kyoto, Japan

IFMIF International Team

JAERI-Review 2004-008, 219 Pages, 2004/03

JAERI-Review-2004-008.pdf:35.23MB

The IFMIF Technical Meeting was held on December 4-5, 2003 at Shiran-kaikan, Kyoto University. The main objectives are (i) to finalize the Comprehensive Design Report (CDR), (ii) to discuss IFMIF cost and organization, (iii) to review technical status of major systems, transition phase activities and EVEDA plan. This report presents a brief summary of the results of the meeting. Agenda, participants list and presentation materials are attached as Appendix.

X-ray structural studies on elemental liquids under high pressures

Katayama, Yoshinori; Tsuji, Kazuhiko*

Journal of Physics; Condensed Matter, 15(36), p.6085 - 6103, 2003/09

https://doi.org/10.1088/0953-8984/15/36/302

X-ray structural studies on several elemental liquids under high pressure are reviewed. Combination of synchrotron radiation sources and large volume presses enables us to carry out in-situ structural measurements on liquids at high pressures up to several GPa. The measurements have revealed that compressions of liquid alkali metals are almost uniform, whereas those of liquids that have covalent components in bonding are mostly anisotropic. In some elements, different types of volume dependence of the nearest neighbour distances are observed in different pressure ranges. This behaviour suggests that the liquid phase can be divided in regions. Although most of the observed structural changes are continuous, a discovery of an abrupt structural change in liquid phosphorus, which is completed over a pressure range of less than 0.05 GPa around 1GPa and 1050 C, supports existence of a first-order liquid-liquid phase transition.

Single crystal growth and magnetic properties of ferromagnetic URhGe

Matsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Andrei, G.; Yamamoto, Etsuji; Okubo, Tomoyuki*; Onuki, Yoshichika

Acta Physica Polonica B, 34(2), p.1071 - 1074, 2003/02

http://www.actaphys.uj.edu.pl/_cur/store/vol34/pdf/v34p1071.pdf

We have successfully grown a single crystal of uranium intermetallic compound URhGe. The temperature dependence of electrical resistivity shows highly anisotropic behavior. Two anomalies, which correspond to the magnetic ordering temperatures, were observed in the resistivity, magnetic susceptibility and specific heat measurements at = 30 K and =25 K. The magnetic susceptibility also shows a large uniaxial anisotropy with a magnetic easy-axis along the [010] direction.

Defect-induced phase separation in relaxor Pb(InNb)O crystals

Yoneda, Yasuhiro; Matsumoto, Norimasa; Terauchi, Hikaru*; Yasuda, Naohiko*

Journal of Physics; Condensed Matter, 15(3), p.467 - 474, 2003/01

https://doi.org/10.1088/0953-8984/15/3/311

Thermal properties of ordered and disordered Pb(InNb)O (PIN) single clystals were investigated. The defect-induced phase separation provided a good agreement of the instability of the relaxor nd antiferroelectric states of the PIN crystals.