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Maeda, Soshu*; Nago, Makito*; Aoyagi, Kazuhei; Sugawara, Kentaro*; Kodama, Junichi*
Shigen, Sozai Koenshu (Internet), 12(2), 5 Pages, 2025/09
no abstracts in English
Kawashima, Hiroyuki; Kurosawa, Takuma*; Teshigawara, Makoto; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi; Kogawa, Hiroyuki
Advanced Experimental Mechanics, 7, p.43 - 48, 2022/08
Laser cutting is expected for reducing the volume of radioactive components by taking account of radioactive levels. The scattering of radioactive dust such as fume and spatter, which is generated throughout the laser cutting process, gets to be a major issue for practical usage in cutting highly radioactive substances. One of driving forces of the spatter is likely to be attributed to the cavitation bubble collapsing caused by rapid thermal loading due to laser irradiation. In order to elucidate the mechanism of spattering, the technique of spark discharge in water was availed to generate the cavitation bubble. The growth and collapse behaviors influenced by the interaction between a free surface and bubbles resulting the spattering phenomena are observed by using an ultra-high-speed video camera, and the numerical simulation was carried out as well.
Madokoro, Hiroshi; Sato, Ikken
Nuclear Engineering and Design, 376, p.111123_1 - 111123_15, 2021/05
Times Cited Count：12 Percentile：71.67(Nuclear Science & Technology)Hasegawa, Kunio; Li, Y.; Kim, Y.-J.*; Lacroix, V.*; Strnadel, B.*
Journal of Pressure Vessel Technology, 141(3), p.031201_1 - 031201_5, 2019/06
Times Cited Count：1 Percentile：4.06(Engineering, Mechanical)When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by Fitness-For-Service (FFS) codes. However, specific criteria of the rules are different amongst these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with two circumferential similar flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with two similar flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with two similar flaws are compared with the stresses in compliance with the flaw combination criteria. It is shown that the calculated plastic collapse stresses based on the flaw combination criteria are significantly different from the experimental and analytical stresses.
from alpha spectroscopyAsai, Masato; He
berger, F. P.*; Lopez-Martens, A.*
Nuclear Physics A, 944, p.308 - 332, 2015/12
Times Cited Count：69 Percentile：95.87(Physics, Nuclear)Nuclear structure of Z = 100-109 nuclei studied through 
-decay spectroscopy have been reviewed. Experimental techniques and methods concerning separation techniques, summing effects in spectra, and the use of digital electronics for -decay spectroscopy have been described in detail. The presentation of the experimental results and the physics discussion were focused on nuclear structure systematics in even-Z nuclei along the N = 151, 153, and 155 isotonic lines, where most progress has been achieved in the last 10 years.
Ueta, Shohei; Shaimerdenov, A.*; Gizatulin, S.*; Chekushina, L.*; Honda, Masaki*; Takahashi, Masashi*; Kitagawa, Kenichi*; Chakrov, P.*; Sakaba, Nariaki
Proceedings of 7th International Topical Meeting on High Temperature Reactor Technology (HTR 2014) (USB Flash Drive), 7 Pages, 2014/10
A capsule irradiation test with the high temperature gas-cooled reactor (HTGR) fuel is being carried out using WWR-K research reactor in the Institute of Nuclear Physics of the Republic of Kazakhstan (INP) to attain 100 GWd/t-U of burnup under normal operating condition of a practical small-sized HTGR. This is the first HTGR fuel irradiation test for INP in Kazakhstan collaborated with Japan Atomic Energy Agency (JAEA) in frame of International Science and Technology Center (ISTC) project. In the test, TRISO coated fuel particle with low-enriched UO
(less than 10% of 
U) is used, which was newly designed by JAEA to extend burnup up to 100 GWd/t-U comparing with that of the HTTR (33 GWd/t-U). Both TRISO and fuel compact as the irradiation test specimen were fabricated in basis of the HTTR fuel technology by Nuclear Fuel Industries, Ltd. in Japan. A helium-gas-swept capsule and a swept-gas sampling device installed in WWR-K were designed and constructed by INP. The irradiation test has been started in October 2012 and will be completed up to the end of February 2015. The irradiation test is in the progress up to 69 GWd/t of burnup, and integrity of new TRISO fuel has been confirmed. In addition, as predicted by the fuel design, fission gas release was observed due to additional failure of as-fabricated SiC-defective fuel.
Oyama, Naoyuki; Sakamoto, Yoshiteru; Isayama, Akihiko; Takechi, Manabu; Gohil, P.*; Lao, L. L.*; Snyder, P. B.*; Fujita, Takaaki; Ide, Shunsuke; Kamada, Yutaka; et al.
Nuclear Fusion, 45(8), p.871 - 881, 2005/08
Times Cited Count：127 Percentile：94.96(Physics, Fluids & Plasmas)The grassy ELM is characterized by the high frequency periodic collapse up to 
kHz, which is 15 times faster than that for type I ELM. A divertor peak heat flux due to grassy ELMs is less than 10% of that for type I ELMs. This smaller heat flux is caused by narrower radial extent of the collapse of temperature pedestal. The different radial extent between type I ELMs and grassy ELMs qualitatively agrees with the different radial distribution of the eigen function of the ideal MHD stability analysis. The ratio of ELM energy loss for grassy ELMs to the pedestal stored energy was 0.4-1%. In high triangularity regime, ELM amplitude, frequency and type can be changed from type I ELM to high frequency grassy ELM as counter plasma rotation was increased. In low triangularity regime, on the other hand, the complete ELM suppression (QH-mode) has been achieved, when the plasma position is optimized with CTR-NBIs. The existence of the edge fluctuations localized in pedestal region may reduce the pedestal pressure, and therefore the QH-mode can be sustained for long time up to 3.4s.
Fujii, Yasuhiko
Koatsuryoku No Kagaku To Gijutsu, 14(2), p.113 - 118, 2004/05
no abstracts in English
Kikuchi, Taiji; Ishikawa, Kazuyoshi; Matsui, Yoshinori; Itabashi, Yukio
JAERI-Tech 2004-043, 21 Pages, 2004/03
JAERI-Tech-2004-043.pdf:2.73MB
In the JMTR, the irradiation examinations for nuclear reactor material are usually requested high accurate irradiation temperature, neutron fluence and neutron spectrum. The general demands satisfy to choice the best irradiation hole in the JMTR. However, for more accuracy, it is necessary to produce capsule with special mechanisms. To get the expectant neutron spectrum (ratio of fast neutron and thermal neutron), the thickness of cadmium is calculated by nuclear calculation code. Cadmium is the material to absorb the thermal neutron. Therefore, the necessary thickness was plated the outside of the specimen container with the cadmium. This paper is reported (1) the various base examinations for the development, (2) the result of the evaluations and (3) the evaluation result of an actual irradiation examination about uniform irradiation capsule of the reversing mechanism.
Kikuchi, Taiji; Yamada, Hirokazu*; Saito, Takashi; Nakamichi, Masaru; Tsuchiya, Kunihiko; Kawamura, Hiroshi
JAERI-Tech 2004-026, 28 Pages, 2004/03
JAERI-Tech-2004-026.pdf:2.06MB
Iirradiation capsule for irradiation test of tritium breeder and inner capsule for pebble bed of tritium breeder is inserted. Post irradiation examination of tritium breeder will be performed after irradiation test. On cutting of irradiation capsule, sweep gas line should be sealed to prevent the tritium gas release or inflow of water to sweep gas line. However, general valve and plug cannot apply to sweep gas line sealing because of the effect of neutron irradiation or limited space in irradiation capsule. Therefore, sealing plug for sweep gas line sealing has to be developed. This report shows the development of sealing plug for sweep gas line sealing and operating procedure of sealing plug in irradiation capsule.
Oyama, Naoyuki; Miura, Yukitoshi; Chankin, A. V.; Takenaga, Hidenobu; Asakura, Nobuyuki; Kamada, Yutaka; Oikawa, Toshihiro; Shinohara, Koji; Takeji, Satoru
Nuclear Fusion, 43(10), p.1250 - 1257, 2003/10
Times Cited Count：16 Percentile：44.71(Physics, Fluids & Plasmas)no abstracts in English
Minehara, Eisuke
Hoshasen To Sentan Iryo Gijutsu, p.135 - 142, 2003/06
Medical applications of Free-Electron Lasers(FELs), especially the FEL driven by a superconducting rf linac, look very promising because of the compactness, high efficiency, high power capability, tunability, ultra-short pulse width and so on. Here, the linac-based FEL is explained briefly and discussed all about the remarkable features and the road maps near future. Finally, some possible and usable applications of the FELs will be introduced and discussed in the relationship with the features above.
Tobita, Masahiro*; Matsui, Yoshinori
JAERI-Tech 2003-042, 132 Pages, 2003/03
JAERI-Tech-2003-042.pdf:7.19MB
Prediction of irradiation temperature is one of the important issues in the design of the capsule for irradiation test. Many kinds of capsules with complex structure have been designed for recent irradiation requests, and three-dimensional (3D) temperature calculation becomes inevitable for the evaluation of irradiation temperature. For such 3D calculation, however, many works are usually needed for input data preparation, and a lot of time and resources are necessary for parametric studies in the design. To improve such situation, JAERI introduced 3D-FEM (finite element method) code NISA (Numerically Integrated elements for System Analysis) and developed several subprograms, which enabled to support input preparation works in the capsule design. The 3D temperature calculation of the capsule are able to carried out in much easier way by the help of the subprograms, and specific features in the irradiation tests such as non-uniform gamma heating in the capsule, becomes to be considered.
lrradiated p-channel 6H-SiC MOSFETs; High total doseLee, K. K.; Oshima, Takeshi; Ito, Hisayoshi
IEEE Transactions on Nuclear Science, 50(1), p.194 - 200, 2003/02
Times Cited Count：34 Percentile：86.90(Engineering, Electrical & Electronic)p-channel SiC MOSFETs were fabricated on n-type 6H-SiC epitaxial layer. The effects of -ray irradiation on the charecteristics of the MOSFETs were studied. Threshold voltage shifts to negative voltage side and the channel mobility reduces due to irradiation. Although the degradation of the channel mobility of the p-channel SiC MOSFETs is 10 times faster than n-channel SiC MOSFETs, p-channel SiC MOSFETs show 100 times stronger radiation resistance than Si MOSFETs. The values of interface traps and oxide-trapped-charge generated sue to irradiation were estimated from the subthreshold characteristics. As the result,it is concluded that the decrease in channel mobility can be explained by the generation of interface traps.
Matsumoto, Taro; Tokuda, Shinji; Kishimoto, Yasuaki; Naito, Hiroshi*
Physics of Plasmas, 10(1), p.195 - 203, 2003/01
Times Cited Count：5 Percentile：16.29(Physics, Fluids & Plasmas)Effects of density gradient on the collisionless m=1 internal kink mode in a cylindrical tokamak plasma are studied by the gyro-kinetic particle simulations. When the density gradient is not large enough to change the full reconnection process, the phenomena after the full reconnection, such as the secondary reconnection and the evolution of the safety factor profile, are changed considerably due to the self-generated radial electric field, i.e. the m=0 mode. The growing mechanism is explained by the difference of 
drift motion between ions and electrons, which is caused by the fast parallel motion of electron. Once the radial electric field is triggered by the symmetrical flow induced by the m=1 mode, the m=0 mode grows up to the same level as the m=1 mode, and drives an plasma rotation in the ion diamagnetic direction, which breaks the symmetrical plasma flow induced by the m=1 mode. The density and current distributions, and minimum safety factor after the full reconnection, are found to be affected by the asymmetrical flow driven by the m=1 and m=0 modes.
Ide, Hiroshi; Matsui, Yoshinori; Itabashi, Yukio; Komori, Yoshihiro; Nagao, Yoshiharu; Komukai, Bunsaku; Tsuji, Hirokazu; Akimoto, Hajime; Onuki, Akira; Araya, Fumimasa
JAERI-Tech 2002-079, 58 Pages, 2002/10
JAERI-Tech-2002-079.pdf:5.92MB
no abstracts in English
Matsui, Yoshinori; Kikuchi, Taiji; Kakuta, Tsunemi
JAERI-Tech 2002-060, 23 Pages, 2002/08
JAERI-Tech-2002-060.pdf:4.42MB
Recently, the number of in-situ tests using optical fibers as signal transmission lines is increasing in the JMTR, because of their noise-tolerant capability and recent development of irradiation proof type fibers. The convensional seal methods, however, have the problem of trust when they applied to the penetration of the irradiation capsule using optical fibers. As the solution of the problem, we selected soldering seal method that was already applied to the deep-sea optical fiber cables and, as its modification, the silver alloy brazing method. From the result of the out-of-pile test, it was confirmed that both soldering seal and silver alloy brazing seal would be applicable to the plug seal of irradiation capsules. Then the soldering seal was applied to a capsule with optical fibers and was irradiated for 5 operation cycles of the JMTR (about 3000 hours). No deterioration was found at the seal after irradiation. This suggested that in-core use of optical fiber was thought to be promising.
Tobita, Masahiro*; Itabashi, Yukio
JAERI-Tech 2002-042, 40 Pages, 2002/03
JAERI-Tech-2002-042.pdf:2.09MB
In relation to aging of light water reactors (LWRs), Irradiation Assisted Stress Corrosion Cracking (IASCC) has been regarded as a significant and urgent issue for reliability of in-core components of LWRs. It is essential for IASCC studies to irradiate test materials under well-controlled of Boiling Water Reactor (BWR) conditions simulating the in-core environment. Therefore, the study for the design of the new water control unit to supply high temperature water into saturated temperature capsules in the Japan Materials Testing Reactor (JMTR) has been carried out. This report summarizes the results of estimation using ORIGEN-2 and QAD-CGGP2 codes of dose equivalent rate on outer surface of the concrete wall of installation room and dose equivalent rate around the ion-exchangers where the highest dose equivalent rate is expected in the unit after the reactor shutdown.
Tobita, Masahiro*; Matsui, Yoshinori
KAERI/GP-195/2002, p.87 - 95, 2002/00
In the Japan Materials Testing Reactor (JMTR) of Japan Atomic Energy Research Institute (JAERI), the temperature distribution inside of irradiation specimens and capsules structure material are evaluated in the design of irradiation capsules. For the evaluation of detailed temperature distribution, NISA (Numerically Integrated elements for System Analysis) code has been introduced, and subprograms are developed to simplify the input data of the capsules structure and the analysis conditions using the three-dimensional finite element method. By the development of subprograms, prediction of the temperature distribution inside of irradiation specimens and capsules structure material became detailed and more accurate than calculation by one-dimensional code. Also estimation of detail temperature distribution during irradiation became possible based on the indication of thermocouple.
Kanno, Masaru; Kitajima, Toshio; Homma, Kenzo
KAERI/GP-195/2002, p.71 - 75, 2002/00
Recent irradiation studies aiming at clarifying the detailed mechanisms of irradiation damages to the reactor materials require to maintain the specimens at constant temperature regardless of the reactor power level,in order to avoid artificial effects of temperature transient due to reactor power change. In order to deal with this problem, JMTR has adopted feed-foward control to the gas pressure based on the reactor power signal, and developed new temperature control technique in combination with feedback control of heater power.
