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Journal Articles

Tracer diffusion coefficients measurements on LaPO $_{4}$ -dispersed LATP by means of neutron radiography

Song, F.*; Chen, H.*; Hayashida, Hirotoshi*; Kai, Tetsuya; Shinohara, Takenao; Yabutsuka, Takeshi*; Yao, Takeshi*; Takai, Shigeomi*

Solid State Ionics, 377, p.115873_1 - 115873_6, 2022/04

https://doi.org/10.1016/j.ssi.2022.115873

Times Cited Count：2 Percentile：31.08(Chemistry, Physical)

Journal Articles

Experimental analysis on dynamics of liquid molecules adjacent to particles in nanofluids

Hashimoto, Shunsuke*; Nakajima, Kenji; Kikuchi, Tatsuya*; Kamazawa, Kazuya*; Shibata, Kaoru; Yamada, Takeshi*

Journal of Molecular Liquids, 342, p.117580_1 - 117580_8, 2021/11

https://doi.org/10.1016/j.molliq.2021.117580

Times Cited Count：3 Percentile：27(Chemistry, Physical)

Quasi-elastic neutron scattering (QENS) and pulsed-field-gradient nuclear magnetic resonance (PFGNMR) analyses of a nanofluid composed of silicon dioxide (SiO $_{2}$ ) nanoparticles and a base fluid of ethylene glycol aqueous solution were performed. The aim was to elucidate the mechanism increase in the thermal conductivity of the nanofluid above its theoretical value. The obtained experimental results indicate that SiO $_{2}$ particles may decrease the self-diffusion coefficient of the liquid molecules in the ethylene glycol aqueous solution because of their highly restricted motion around these nanoparticles. At a constant temperature, the thermal conductivity increases as the self-diffusion coefficient of the liquid molecules decreases in the SiO $_{2}$ nanofluids.

Journal Articles

Optimum temperature for HIP bonding invar alloy and stainless steel

Wakui, Takashi; Ishii, Hideaki*; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Wakai, Eiichi; Takada, Hiroshi; Futakawa, Masatoshi

Materials Transactions, 60(6), p.1026 - 1033, 2019/06

https://doi.org/10.2320/matertrans.M2018346

Times Cited Count：3 Percentile：17.96(Materials Science, Multidisciplinary)

The mercury target has large size as 1.31.32.5 m $^{3}$ . In view of reducing the amount of wastes, we studied the structure so that the fore part could be separated. The flange is required to have high seal performance less than 110 $^{-6}$ Pa m $^{3}$ /s. Invar with low thermal expansion is a candidate. Due to its low stiffness, however, the flange may deform when it is fastened by bolts. Practically invar is reinforced with stainless steel where all interface between them has to be bonded completely with the HIP bonding. In this study, we made specimens at four temperatures and conducted tensile tests. The specimen bonded at 973 K had little diffusion layer, and so fractured at the interface. The tensile strength reduced with increasing the temperature, and the reduced amount was about 10% at 1473 K. The analyzed residual stresses near the interface increased by 50% at maximum. Then, we concluded that the optimum temperature was 1173 K.

Journal Articles

Direct observation of fast lithium-ion diffusion in a superionic conductor; Li $_{7}$ P $_{3}$ S $_{11}$ metastable crystal

Mori, Kazuhiro*; Enjuji, Keigo*; Murata, Shun*; Shibata, Kaoru; Kawakita, Yukinobu; Yonemura, Masao*; Onodera, Yohei*; Fukunaga, Toshiharu*

Physical Review Applied (Internet), 4(5), p.054008_1 - 054008_6, 2015/11

https://doi.org/10.1103/PhysRevApplied.4.054008

Times Cited Count：41 Percentile：82.07(Physics, Applied)

no abstracts in English

Journal Articles

Application of invasion mathematical model in dosimetry for boron neutron capture therapy for malignant glioma

Yamamoto, Kazuyoshi; Kumada, Hiroaki; Nakai, Kei*; Endo, Kiyoshi*; Yamamoto, Tetsuya*; Matsumura, Akira*

Proceedings of 11th World Congress on Neutron Capture Therapy (ISNCT-11) (CD-ROM), 14 Pages, 2004/10

A dose distribution considered the tumor cell density distribution is required on the radiation therapy. We propose a novel method of determining target region considering the tumor cell concentration as a new function for the next generation Boron Neutron Capture Therapy (BNCT) dosimetry system. It has not been able to sufficiently define the degree of microscopic diffuse invasion of the tumor cells peripheral to a tumor bulk in malignant glioma using current medical imaging. Referring to treatment protocol of BNCT, the target region surrounding the tumor bulk has been set as the region which expands at the optional distance with usual 2cm margin from the region enhanced on T1 weighted gadolinium Magnetic Resonance Imaging (MRI). In this research, the cell concentration of the region boundary of the target was discussed by using tumor cell diffusion model in the sphere spatio-temporal system. The survival tumor cell density distribution after the BNCT irradiation was predicted by the two regions diffusion model for a virtual brain phantom.

Journal Articles

Introduction to modern nodal method and discontinuity factor

Okumura, Keisuke

Nihon Genshiryoku Gakkai Dai-36-Kai Robutsuri Kaki Semina Tekisuto, p.81 - 102, 2004/08

The modern node method which uses a discontinuous factor has come to be widely used recently in the reactor core analyses of commercial light water reactors. The basic theory, numerical computation technique and examples of calculation results are explained for biginners of the modern nodal method.

JAEA Reports

Evaluation for the models of neutron diffusion theory in terms of power density distributions of the HTTR

Takamatsu, Kuniyoshi; Shimakawa, Satoshi; Nojiri, Naoki; Fujimoto, Nozomu

JAERI-Tech 2003-081, 49 Pages, 2003/10

JAERI-Tech-2003-081.pdf:2.6MB

In the case of evaluations for the highest temperature of the fuels in the HTTR, it is very important to expect the power density distributions accurately; therefore, it is necessary to improve the analytical model with the neutron diffusion and the burn-up theory. The power density distributions are analyzed in terms of two models, the one mixing the fuels and the burnable poisons homogeneously and the other modeling them heterogeneously. Moreover these analytical power density distributions are compared wtih the ones derived from the gross -ray measurements and the Monte Carlo calculational code with continuous energy. As a result the homogeneous mixed model isn't enough to expect the power density distributions of the core in the axial direction; on the other hand, the heterogeneous model improves the accuracy.

JAEA Reports

Analysis of the applicability of acceleration methods for a triangular prism geometry nodal diffusion code

Fujimura, Toichiro*; Okumura, Keisuke

JAERI-Research 2002-024, 27 Pages, 2002/11

JAERI-Research-2002-024.pdf:1.04MB

A prototype version of a diffusion code has been developed to analyze the hexagonal core as reduced moderation reactor and the applicability of some acceleration methods have been investigated to accelerate the convergence of the iterative solution method. The hexagonal core is divided into regular triangular prisms in the three-dimensional code MOSRA-Prism and a polynomial expansion nodal method is applied to approximate the neutron flux distribution by a cubic polynomial. The multi-group diffusion equation is solved iteratively with ordinal inner and outer iterations and the effectiveness of acceleration methods is ascertained by applying an adaptive acceleration method and a neutron source extrapolation method, respectively. The formulation of the polynomial expansion nodal method is outlined in the report and the local and global effectiveness of the acceleration methods is discussed with various sample calculations. A new general expression of vacuum boundary condition, derived in the formulation is also described.

JAEA Reports