Evaluation of the characteristics of metal nitrate aqueous solutions by microwave heating and the morphologies of synthesized metal oxide powders

Segawa, Tomomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Fukasawa, Tomonori*; Fukui, Kunihiro*

Funtai Kogakkai-Shi, 57(9), p.485 - 494, 2020/09

In the spent fuel reprocessing process, a mixed solution of uranyl nitrate and plutonium nitrate is converted into mixed oxide powder by the microwave heating. To evaluate the applicability to the industrial-scale and acquire the characteristics data of the microwave heating denitration of various metal nitrate aqueous solutions based on the knowledge studied in the development of laboratory-scale basic experiments, the microwave heating characteristics and metal oxide powder properties were investigated using cerium nitrate, cobalt nitrate and copper nitrate aqueous solutions. The progress rate of the denitration reaction was depended on the position, and the denitration reaction proceeded faster at the periphery than at the center. The morphologies of the synthesized products were porous and hard dry solid with cerium nitrate aqueous solution, foamed dry solid with cobalt nitrate aqueous solution, and powdery particles with copper nitrate aqueous solution. The denitration ratio and average particle size of the synthesized products increased in the order of the cerium nitrate aqueous solution, the cobalt nitrate aqueous solution, and the copper nitrate aqueous solution. The numerical simulations revealed that the periphery of the bottom surface of the metal nitrate aqueous solution was heated by microwaves. This results consistent with the experimental results in which the denitration reaction started from the periphery of the metal nitrate aqueous solution.

Preparation of Computational Science Simulation Code SPLICE for Laser Manufacturing Process; Research activities on FY2019

Muramatsu, Toshiharu

JAEA-Research 2019-008, 111 Pages, 2019/11

JAEA-Research-2019-008.pdf:8.64MB

A general-purpose three-dimensional thermohydraulics numerical simulation code SPLICE (residual Stress control using Phenomenological modeling for Laser welding repair process In Computational Environment) was designed to deal with gas-liquid-solid consolidated incompressible viscous flows with a phase change process in various laser applications. Main features of the SPLICE code are as follows: (1) A multi-scale model is used to simulate complicated phenomena, such as welding to solidification of metal materials, thermal and mechanical interactions among gas, liquid and solid phases, etc., (2) SPLICE code is applicable for the evaluation of welding, cutting, piercing, coating, additive manufacturing, etc. and (3) A graphic user interface (GUI) is prepared for users to easy utilization of the SPLICE code. This report describes the details of the mathematics, physics, numerics, sample applications of the SPLICE code.

Interpretation of thermal desorption spectra of hydrogen from aluminum using numerical simulation

Ebihara, Kenichi; Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro

Keikinzoku, 68(11), p.596 - 602, 2018/11

Hydrogen embrittlement (HE) is considered as one cause of stress corrosion cracking. HE is a serious problem in the development of high strength aluminum alloy as with steels. For understanding HE, it is inevitable to know hydrogen trapping states in the alloys and it can be identified using thermal desorption spectrometry of H. In this study, we numerically simulated thermal desorption spectra of hydrogen in aluminum for a cylindrical and a plate specimens and interpreted the desorption peaks included in them on the basis of the trap site concentration and the trap energy. As a result, we found that the peak at the lowest-temperature side can result from grain boundaries and confirmed that the reported interpretation for other peaks is reasonable. We also obtained the result showing the possibility that the trap site concentration of defects changes during heating the specimens. This result may give a suggestion for the interpretation of temperature desorption spectra of steels.

Numerical simulation of hydrogen thermal desorption profile under assumption of two kinds of trap sites for tempered martensitic steel

Tsuchida, Yutaka*; Ebihara, Kenichi

Tetsu To Hagane, 103(11), p.653 - 659, 2017/11

https://doi.org/10.2355/tetsutohagane.TETSU-2017-039

A single peak in thermal desorption profiles of hydrogen, which are measured in low-temperature thermal desorption spectrometry (L-TDS) for a very thin plate specimen of tempered martensitic steel, was reproduced successfully by the superposition of two Gaussian distributions. Then, the parameters concerning the detrapping rate constants for both peaks, which are trap energy and pre-exponential factor, were calculated using the Choo-Lee plot. We confirmed that Kissinger model incorporating the obtained parameters could simulate the two peaks. In addition, we reproduced the single peak well using the reaction-diffusion equation incorporating the obtained parameters and the appropriate trap site concentration. From the results, we interpreted that the one peak corresponds to dislocation and the other to grain-boundary.

Validation of measured microwave absorption and temperature change for development of a single-mode-type microwave heating thermogravimetry apparatus

Karisma, A. D.*; Hamaba, Taishu*; Fukasawa, Tomonori*; Huang, A.-N.*; Segawa, Tomomi; Fukui, Kunihiro*

Review of Scientific Instruments, 88(2), p.024101_1 - 024101_8, 2017/02

https://doi.org/10.1063/1.4974813

Microwave heating direct denitration method is used in the nuclear fuel reprocessing process. In order to develop a single-mode-type microwave heating thermogravimetry apparatus which can perform detailed analysis of the characteristics of microwave heating, the temperature dependence of microwave absorption is verified. The temperature distribution, microwave absorption efficiency, and dielectric properties of a CuO pellet that was heated by the microwave irradiation were investigated. The temperature distribution in the CuO pellet due to one-way travel of the microwave in the apparatus was accurately reproduced by a three-dimensional numerical simulation of the electromagnetic field. The numerically determined temperature dependency of the CuO absorption efficiency was found to be in very good agreement with published data.

Study on modeling of thermal desorption spectra of hydrogen including variation of vacancy-type trap sites

Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*

"Suiso Zeika No Kihon Yoin To Tokusei Hyoka Kenkyukai Chukan Hokokukai" Shimposium Yokoshu (USB Flash Drive), p.30 - 35, 2016/09

no abstracts in English

Numerical reproduction of hydrogen thermal desorption spectra of tempered martensitic steel based on experimental data

Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*

"Suiso Zeika No Kihon Yoin, Kaiseki To Hyoka" Shimposium Yokoshu (USB Flash Drive), p.27 - 33, 2015/09

The thermal desorption spectra which reflect the H segregation state can be obtained by heating a specimen including H at a constant rate. However, the simulation of spectra needs to extract information of the H segregation state because spectra is affected by experimental conditions and H diffusion. The detrapping activation energy E and the pre-exponential factor of detraping rate constant which are simulation parameters are fixed from the data previously reported or by fitting experimental spectra. Instead, we evaluated both of them from the experimental spectra of the specimen in which the H diffusion effect can be ignored, and simulated the spectra using them. As a result, in the case of iron, we could simulate spectra better than by the previous parameters. In the case of tempered martensitic steel, we could simulate spectra by the value obtained by adjusting the evaluated p along with the evaluated E.

Numerical simulation of turbulent heat transfer behind a spacer with small-ribs in a subchannel

Takase, Kazuyuki

Proceedings of OECD/NEA & IAEA Workshop on Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation (CFD4NRS-5) (Internet), 11 Pages, 2014/09

When devising the thermal design of supercritical water reactors, it is necessary to develop an analysis method that correctly predicts the turbulent heat transfer characteristics in subchannels of fuel bundles. Spacers are set into the subchannels to maintain the distances between adjacent fuel rods. The turbulent heat transfer is generally enhanced by the spacers' reduction of the cross-sectional area in the subchannels. However, since the thermophysical properties of supercritical fluids drastically change in the vicinity of a pseudocritical point, the enhancement of the turbulent heat transfer depends on the thermal design. To this end, the Japan Atomic Energy Agency is developing an analysis method that will predict the thermal-hydraulic characteristics of supercritical fluids. The heat transfer calculations were performed using a newly developed code under conditions of a subchannel with a spacer. The enhancement of the turbulent heat transfer coefficient in the subchannels with spacers was analyzed numerically.

Unknown characteristic frequency of a multibubble system in a sound field; Theoretical prediction and numerical verification using an improved CIP-CUP

Ida, Masato

Proceedings of 6th World Congress on Computational Mechanics in conjunction with 2nd Asian-Pacific Congress on Computational Mechanics (CD-ROM), p.1 - 11, 2004/09

The existence of the "transition frequencies" of two acoustically coupled gas bubbles has been verified by direct numerical simulation. The theory described by Ida [Phys. Lett. A 297 (2002) 210] predicted that a bubble in the double-bubble system has three transition frequencies, some of which makes the phase difference between the bubble's volume oscillation and an external sound without accompanying resonance response of the bubble. In a more recent paper [Ida, Phys. Rev. E 67 (2003) 056617], it was suggested theoretically that one of the transition frequencies may cause the sign reversal of the secondary Bjerknes force acting between pulsating bubbles. In the present study, we employ a direct numerical simulation technique that uses the compressible Navier-Stokes equations with a surface-tension term as the governing equations to investigate the transition frequencies of two coupled bubbles. The numerical results clearly exhibit the existence of the theoretically predicted characteristic frequency.

Development of an integrated numerical simulation infrastructure for fluid-structure coupled problems

Hazama, Osamu; Guo, Z.

Keisan Kogaku Koenkai Rombunshu, 8(2), p.759 - 760, 2003/05

no abstracts in English