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Kamiya, Junichiro; Morohashi, Yuko
Kurin Tekunoroji, 35(1), p.39 - 42, 2025/01
no abstracts in English
Kamiya, Junichiro; Abe, Kazuhide; Fujimori, Shinichi; Fukuda, Tatsuo; Kobata, Masaaki; Morohashi, Yuko; Tsuda, Yasutaka; Yamada, Ippei; Yoshigoe, Akitaka
e-Journal of Surface Science and Nanotechnology (Internet), 22(4), p.316 - 326, 2024/08
The activation and deterioration mechanisms of the Ti-Zr-V non-evaporable getter (NEG) coating have been investigated. Operando analysis of the surface chemical composition change of the Ti-Zr-V coating was performed by the synchrotron radiation photoelectron spectroscopy (SRPES) during the process of raising the sample temperature to 250C, corresponding to the activation process of NEG coating. The surface oxidation process was also characterized by the SRPES during the injection of O_2 gas into the chamber while keeping the sample temperature at 250
C, corresponding to the deterioration process of NEG coating, i.e. surface oxidation and oxygen diffusion to the coating interior. The depth profile of the oxidized sample was measured with X-ray photoelectron spectroscopy. The results shows, in the activation process, the surface Zr gets the oxygen from the oxides of Ti and V at the first stage, resulting in the metallic Ti and V on the surface, and the oxygen of the Zr-oxide and/or Zr sub-oxides diffuse to the interior of the coating in the continuous temperature rise, resulting in the metallic Zr on the surface. It is further suggested that the deterioration of the Ti-Zr-V NEG coating means the Zr and secondary Ti are oxidized deep into the coating, resulting in the restriction of the oxygen migration from the NEG compositions on the surface and consequently the lack of surface metallization.
Sato, Yuki; Kakuto, Takeshi*; Tanaka, Takayuki*; Shimano, Hiroyuki*; Morohashi, Yuko; Hatakeyama, Tomoyoshi*; Nakajima, Junsaku; Ishiyama, Masahiro
Nuclear Instruments and Methods in Physics Research A, 1063, p.169300_1 - 169300_7, 2024/06
Times Cited Count:1 Percentile:75.38(Instruments & Instrumentation)Aizawa, Kosuke; Chikazawa, Yoshitaka; Morohashi, Yuko
Journal of Nuclear Science and Technology, 55(12), p.1393 - 1401, 2018/12
Times Cited Count:2 Percentile:19.05(Nuclear Science & Technology)Measurement of the temperature and flow rate at each fuel subassembly outlet is an effective way for a liquid metal fast breeder reactor to detect a loss of coolant accident or reactivity-initiated accident in the early stage and to understand the reactor's thermal hydrodynamic performance. Japan Atomic Energy Agency has developed the eddy current flowmeter in practical use and installed 34 of them in the upper core structure of fast breeder reactor, Monju. This report presents data obtained by using the flowmeters in Monju. We observed high linearity between each of the flowmeter's signal intensity and the primary sodium's flow rate under 10-100% flow rate condition. The fluctuation of flow rate observed by the flowmeters was below 0.2 m/s which is 5% of the time-averaged velocity under a rated condition. These experimental results show that the eddy current flowmeter is an effective tool to detect the changes in relative flow rate.
Aizawa, Kosuke; Chikazawa, Yoshitaka; Morohashi, Yuko
Proceedings of 2016 International Congress on Advances in Nuclear Power Plants (ICAPP 2016) (CD-ROM), p.314 - 320, 2016/04
Temperature and flow rate measurement of each fuel subassembly outlet is effective to detect loss of coolant accident (LOCA) and reactivity initiated accident (RIA) early and to understand a thermal hydrodynamic performance in liquid metal fast breeder reactor (LMFBR). This report shows the data of eddy current type flow meters in Monju. High linearity between the signal intensity of each eddy current type flow meter and flow rate of primary sodium was obtained in the flow rate condition of 10100%. In addition, the linearity was also demonstrated in the low velocity region, approx. 0.25 m/s. Fluctuation shown on each eddy current type flow meter was below 0.2 m/s, which is 5 % of the time averaged velocity at the rated condition. Those experimental results show that the eddy current type flow meter can detect the change of relative flow rate.
Morohashi, Yuko; Suzuki, Satoshi
JAEA-Technology 2014-045, 116 Pages, 2015/03
The failed fuel detection and location (FFDL) system collects the tagging gas that migrates into the reactor cover gas from a failed pin. The tagging gas is made of stable isotopes of Kr and Xe. The isotopic composition of the tagging gas can be made specific to each assembly. The assembly containing a failed fuel pin can be identified by analyzing the isotopic composition. The FFDL system is comprised of two tagging gas concentration devices. The concentration rate is designed to be higher than 200. Past examinations demonstrated that the concentration rate meets the requirement with a noble gas concentration of 1ppm. However, the actual noble gas concentration emitted from a failed fuel is assumed to be much lower. In the present study, the performance of FFDL system was investigated by measuring low concentration gas of the actual fuel failure level. As a result, the concentration rate was confirmed to be more than tens of thousands, which sufficiently satisfies the design demand.
Morohashi, Yuko; Suzuki, Satoshi
Proceedings of 2014 International Congress on the Advances in Nuclear Power Plants (ICAPP 2014) (CD-ROM), p.624 - 630, 2014/04
Monju has failed fuel detection systems which consist of the delayed neutron (DN) monitoring system, the cover gas (CG) monitoring system, and the failed fuel detection & location (FFDL) system based on the tagging gas analysis. The DN method and the CG method are used to watch the integrity of fuel assemblies continuously. When a fuel failure of pin-hole level is detected by the CG monitoring, the FFDL system starts operation to identify the location of the failed fuel assembly in the reactor core. In case of a larger fuel failure, the DN monitoring system works and the reactor shuts down automatically. The FFDL system collects the tagging gas which migrates into the reactor cover gas from a failed pin. The tagging gas is made of stable isotopes of Kr and Xe. 270 types of isotopic composition are available using 15 types for Kr and 9 types for Xe. Thus, the isotopic composition of the tagging gas can be made specific to each assembly. The assembly containing a failed fuel pin in the reactor core can be identified by analyzing the isotopic composition. The FFDL system is comprised of two tagging gas concentration devices. The device collects and concentrates the tagging gas by adjusting temperature of activated carbon from 110 K to 420 K. The concentration rate is designed to be higher than 200. In the past examination performed, it was confirmed that the concentration rate meets the requirement with a noble gas concentration of 1 ppm. However, the actual noble gas concentration emitted from a failed fuel is assumed to be much lower. In the present study, the performance of FFDL system was demonstrated by measuring low concentration gas of the actual fuel failure level. The sample gas of concentrations ranging 0.1 ppb to 10 ppb was used. As a result, the concentration rate was confirmed to be more than tens of thousands, which sufficiently satisfies the design demand. Moreover, it was confirmed that the concentration dependence of noble gas was small.
Jo, Takahisa; Goto, Takehiro; Yabuki, Kentaro; Ikegami, Kazunori; Miyagawa, Takayuki; Mori, Tetsuya; Kubo, Atsuhiko; Kitano, Akihiro; Nakagawa, Hiroki; Kawamura, Yoshiaki; et al.
JAEA-Technology 2010-052, 84 Pages, 2011/03
The prototype fast breeder reactor MONJU resumed the System Startup Test (SST) on May 6th 2010 after five months and fourteen years shutdown since the sodium leakage of the secondary heat transport system on December 1995. Core Confirmation Test (CCT) is the first step of SST, which consists of three steps. CCT was finished on July 22nd after 78 days tests. CCT is composed 20 test items including control rods' worth evaluation, radiation dose measurement etc..
Morohashi, Yuko; Maruyama, Tadashi*; Donomae, Takako; Tachi, Yoshiaki; Onose, Shoji
Journal of Nuclear Science and Technology, 45(9), p.867 - 872, 2008/09
Times Cited Count:12 Percentile:60.73(Nuclear Science & Technology)Donomae, Takako; Tachi, Yoshiaki; Sekine, Manabu*; Morohashi, Yuko; Akasaka, Naoaki; Onose, Shoji
Journal of the Ceramic Society of Japan, 115(1345), p.551 - 555, 2007/09
Times Cited Count:4 Percentile:28.48(Materials Science, Ceramics)Use of moderator materials in Fast Breeder Reactor (FBR) is effective for transmutation technology, and B
C is one of the candidates. Up to now, the behavior of
B
C as the Control rod material is well known, but that of
B
C is hardly investigated. In this paper, the radiation effects of
B
C pellets, neutron irradiated in the experimental fast reactor JOYO were studied. From the experimental results, it was observed that no macro-cracks were recognized in the irradiated
B
C pellets. But, bubble nucleation was found in grain and along grain boundaries of
B
C. And, it was shown that the conductivity of
B
C was higher than that of
B
C. During the annealing from room temperature to 1400
C, three recovery stages were found on thermal conductivity. It was suggested that, the recovery of B
C was related to the dispersion behavior of helium. Judging from these results, as
B
C was mechanically more stable compared with
B
C under irradiation, it was shown that
B
C had high applicability for a moderator.
Yokoyama, Kenji; Morohashi, Yuko; Maeda, Shigetaka; Sekine, Takashi
JNC TN9400 2004-012, 56 Pages, 2004/03
In the experimental fast reactor JOYO MK-III performance test core, the isothermal temperature coefficient was measured. There was a systematic difference between the result of ascending temperature measuament and that of descending temperature measurement. However, it was removed by the correction of thermal expansion effect of the control rod extension tubes. Finally, -3.82+-0.17x10^-3%dk/kk'/C was obtained as a measured value of the isothermal temperature coefficient. From this result, it was confirmed that isothermal temperature coefficient is a negative value and the calculated design value, -3.88x10^-3%dk/kk'/C, agrees with the measured value well.On the other hand, a detailed analysis based on JUPITER standard analysis method was carried out. In this analysis, transport effects and ultra fine group effects were evaluated. The calculated isothermal temperature coefficient has two main components, Doppler broadening of neutron cross section resonances and thermal expansion of the fuel and core. The items contributing to the thermal expansion include the coolant density reduction, the core radial expansion and the fuel axial expansion. In addition, the isothermal temperature coefficients of the MK-I, MK-II cores were evaluated by using the same method and differences among the cores are discussed. The calculated value by JUPITER standard analysis method became -3.68x10^-3%dk/kk'/C (C/E-value:0.96) and it agrees with the measured value within measurement error.
Morohashi, Yuko; Ishibashi, Junichi;
JNC TN4400 2001-003, 28 Pages, 2002/03
The criticality analysis of the MONJU initial critical core was conducted based on conventional methods developed by the JUPITER program. Effective cross sections were created, considering self-shielding effects, from the JAERI Fast Set (JFS-3-J3.2); group constants in 70 energy groups, which were processed from the Japanese Evaluated Nuclear Data Library (JENDL-3.2). These were used in the standard calculation method: a 3-Dimensional Hexagonal-Z whole core calculation by diffusion theory. This standard calculation, however, involves several approximations. The continuous neutron energy spectrum is divided into 70 discrete energy groups and continuous spatial coordinates are represented by assembly-wise spatial meshes. Original transport equations are solved by diffusion theory (isotropic scattering) approximation and fine structures in fuel assemblies, such as fuel pins or wrapper tubes, are processed into cell-wise homogeneous mixture. To improve the accuracy of the results, these approximations are compensated for by applying corresponding correction factors. Cell heterogeneity effects, among them, were evaluated to be 0.3-0.4% k/kk' by diffusion calculations based on the group constants, obtained by heterogeneous cell model calculations. This method, however, has the drawback that it assumes that there is no interdependency of the related approximations; energy grouping, diffusion approximation, etc. A study on cell heterogeneity effects has been conducted using the continuous energy Monte Carlo method to validate the adequacy of this non-interdependency assumption. As a result, cell heterogeneity effects slightly larger than those from conventional methods have been obtained; 0.54%
k/kk' for the initial critical core, and 0.50%
k/kk' for the initial full power core. Dependency on plutonium enrichment and fuel temperature has also been identified, which implies the dependency of the cell heterogeneity effects on the specific ...
平塚 一; 阿部 哲也; 諸橋 裕子
大間知 聡一郎*
【課題】アルミニウム切粉に付着した切削油および水分を除去または分解するためのキルンを設けることなく、したがってキルンに投入するエネルギーを不要にしたうえで、高純度のアルミニウムをリサイクルできる処理装置を提供する。 【解決手段】アルミニウム溶解炉と、前記アルミニウム溶解炉の上部に設けられた、筒状のサイクロン本体と、前記サイクロン本体内に切削油および水分が付着したアルミニウム切粉を気体とともに流入させる流入口と、前記サイクロン本体内から前記アルミニウム切粉を含まない気体を流出させる流出口とを有するサイクロンユニットとを含むアルミニウム切粉の処理装置。
Kamiya, Junichiro; Abe, Kazuhide; Kobata, Masaaki; Tsuda, Yasutaka; Fukuda, Tatsuo; Fujimori, Shinichi; Morohashi, Yuko; Yamada, Ippei; Yoshigoe, Akitaka
no journal, ,
Sequence measurements with XPS have been performed to understand more detail about the activation and deterioration mechanism. The sample of a titanium plate with Ti-Zr-V coating of 1 um thickness was prepared. The sample was set in the surface science station in the BL23SU of SPring-8. At first, the XPS measurements for the sample surface were performed during the sample temperature was raised to 250C. After that, the XPS was subsequently performed during the injection of oxygen gas into the chamber while keeping the sample temperature at 250
C, which corresponds to the accelerated deterioration test. After that, the depth profile of the sample was measured with another XPS apparatus with an X-ray tube by argon etching. The result showed that the surface Zr gets the oxygen from Ti oxide and V oxide at the first stage of the activation and the oxygen of the Zr oxide would diffuse to the bulk in the continuous temperature rise. It was revealed that the concentrated oxygen in the coating exists in the forms of mainly Zr oxide and Ti oxide in the second place.
Wada, Kaoru*; Shiga, Takashi; Okahashi, Kazunari*; Kamiya, Junichiro; Kobata, Masaaki; Morohashi, Yuko; Abe, Kazuhide; Kishikawa, Shinsuke*; Sasaki, Masanao*; Kuroiwa, Masahide*; et al.
no journal, ,
Tokyo Electronics Co., Ltd. manufactures and sells ultra-high vacuum equipment using BeCu material. By integrating this with the NEG coating technology from the Japan Atomic Energy Agency, the company has developed a getter-type BeCu vacuum chamber that can operate without electricity. In a series of experiments, the chamber was opened to the atmosphere, evacuated, and then subjected to a baking (activation) process at 200 for 8.5 hours, repeated five times. The results showed that the NEG coating significantly improved the pumping speed and reduced the ultimate pressure. Additionally, during buildup pressure measurements, this process was repeated five times. While there was no substantial difference in pressure before the tests, a noticeable improvement in pressure was observed with the NEG coating as the tests progressed. This demonstrates that the NEG coating not only enhances the efficiency of the vacuum system but also plays a crucial role in maintaining an ultra-high vacuum environment.
Kobata, Masaaki; Morohashi, Yuko; Abe, Kazuhide; Yamada, Ippei; Fukuda, Tatsuo; Koarai, Kazuma; Tanida, Hajime; Kamiya, Junichiro
no journal, ,
This study aimed to improve non-evaporable getter (NEG) coating technology on titanium substrates, focusing on lowering activation temperatures and enhancing repeatability. Using Hard X-ray Photoelectron Spectroscopy (HAXPES) and Secondary Ion Mass Spectrometry (SIMS), we analyzed NEG activation and degradation mechanisms. The effects of titanium, stainless steel (SUS316), and beryllium copper (BeCu) substrates on NEG properties were compared. Results suggested that the BeCu substrate had the lowest activation temperature, indicating its potential advantage for low-temperature NEG activation.
Morohashi, Yuko; Kamiya, Junichiro; Warigai, Keiichi*; Takeishi, Kenichi; Kobata, Masaaki; Yoshigoe, Akitaka; Tsuda, Yasutaka; Fukuda, Tatsuo; Yamada, Ippei; Chiba, Daisuke
no journal, ,
no abstracts in English
Kamiya, Junichiro; Wada, Kaoru*; Shiga, Takashi; Morohashi, Yuko
no journal, ,
no abstracts in English
Morohashi, Yuko; Kamiya, Junichiro; Abe, Kazuhide; Kobata, Masaaki; Tsuda, Yasutaka
no journal, ,
no abstracts in English