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Fe
intermetallic compoundCao, Y.*; Zhou, H.*; Khmelevskyi, S.*; Lin, K.*; Avdeev, M.*; Wang, C.-W.*; Wang, B.*; Hu, F.*; Kato, Kenichi*; Hattori, Takanori; et al.
Chemistry of Materials, 35(8), p.3249 - 3255, 2023/04
Times Cited Count：4 Percentile：20.33(Chemistry, Physical)Hydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in HoFe on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level, which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials.
Nakamura, Hironobu; Tanigawa, Masafumi; Mukai, Yasunobu; Nakamichi, Hideo; Umino, Yoshinori; Fujisaku, Sakae; Kimura, Takashi; Kurita, Tsutomu
Proceedings of INMM 56th Annual Meeting (Internet), 8 Pages, 2015/07
In the MOX handling facilities, many types and amount of nuclear materials (NM) that are relatively easy to access are used in a GB. In order to prevent unauthorized removal of NM from the GB by an insider, based on the Japanese regulation which was referred from INFCIRC/225 Rev.5, the 2 person rule are being introduced at the area where NM handling GB are installed. As an example of usage of the security counterplan for the detection of unauthorized removal of NM, a new proposal of detection concept for the unauthorized removal by operators were investigated with implementation of several experiments considering actual GB operation. In general, it is considered that normal concept is to use radiation monitor (
or neutron) to detect the event by checking the variation of monitoring data. However, it is thought that distinguish between authorized NM movement during operation and the unauthorized removal (sample bag-out from GB) is very difficult. To solve this subject, JAEA studied and proposes a new concept about negative pressure monitoring in the GB in addition to the radiation monitoring. It is thought that the hybrid monitoring concept between pressure and radiation provides the detection alarm for it with central alarm station (CAS) accurately and rapidly with high integrity, and helps to complement current 2 person rule.
Sakaba, Nariaki; Iigaki, Kazuhiko; Kondo, Masaaki; Emori, Koichi
Nuclear Engineering and Design, 233(1-3), p.135 - 145, 2004/10
Times Cited Count：6 Percentile：39.64(Nuclear Science & Technology)The containment structures of the HTTR consist of the reactor containment vessel, the service area, and the emergency air purification system, which minimise the release of fission products in postulated accidents which lead to fission product release from the reactor facilities. The reactor containment vessel is designed to withstand the temperature and pressure transients and to be leak-tight in the case of a rupture of the primary concentric hot gas duct, etc. The pressure inside the service area is maintained at a negative pressure by the emergency air purification system. The emergency air purification system will also remove airborne radio-activity and will maintain a correct pressure in the service area. The leak-tightness characteristics of the containment structures are described in this paper. The measured leakage rates of the reactor containment vessel were enough less than the specified leakage limit of 0.1%/d confirmed during the commissioning tests and annual inspections. The service area was kept the design pressure well below its allowable limitation by the emergency air purification system which filter efficiency of particle removal and iodine removal were well over the limited values. The obtained data demonstrates that the reactor containment structures were fabricated to minimise the release of fission products in the postulated accidents with fission product release from the reactor facilities.
Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kikuchi, Kenji; Haga, Katsuhiro; Kaminaga, Masanori; Hino, Ryutaro
JAERI-Tech 2003-093, 55 Pages, 2004/01
JAERI-Tech-2003-093.pdf:5.41MB
To estimate the structural integrity of the heavy liquid-metal (Hg) target used in a MW-class neutron scattering facility, static and dynamic stress behaviors due to the incident of a 1MW-pulsed proton beam were analyzed. In the analyses, two-type target containers with semi-cylindrical type and flat type window were used as analytical models of the structural analysis codes LS-DYNA. As a result, it is confirmed that the stress generated by dynamic thermal shock becomes the largest at the center of window, and the flat type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It was confirmed to erosion damage the target container by mercury's becoming negative pressure in the window and generating the cavitation by the experiment. Therefore, it has been understood that the point top of the window was in the compression stress field by the steady state thermal stress because of the evaluation from destroying the dynamic viewpoint for the crack in the generated pit and the pit point, and the crack did not progress.
Taniguchi, Masaki; Hanada, Masaya; Iga, Takashi*; Inoue, Takashi; Kashiwagi, Mieko; Morishita, Takatoshi; Okumura, Yoshikazu; Shimizu, Takashi; Takayanagi, Tomohiro; Watanabe, Kazuhiro; et al.
Nuclear Fusion, 43(8), p.665 - 669, 2003/08
Times Cited Count：17 Percentile：47.15(Physics, Fluids & Plasmas)no abstracts in English
Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kikuchi, Kenji; Hino, Ryutaro; Arakawa, Chuichi
Journal of Nuclear Materials, 318, p.113 - 121, 2003/05
Times Cited Count：12 Percentile：61.05(Materials Science, Multidisciplinary)The thermal shock stress in the mercury target vessel was analyzed: the target receives the incident proton beam at the energy of 1 MW with the pulse duration of 1ms. Negative pressure of maximal 61MPa was generated when the initial pressure of 52MPa propagated in mercury. It is expected then that the cavitation may be arisen by the negative pressure. So in order to know the cavitation behavior, the simulation study was carried out by using the equation of motion based on the bubble dynamics for a single bubble, and fundamental parameter analysis was carried out. It is found that a bubble has a potential expansion more than 1000 times with a change of the pressure at the window of the target vessel. Consequently wave propagation will be affected. Theoretical consideration was given to the wave motion of propagation in bubbly liquid. The equation of state in bubbly liquid can be approximated by the polynomial. The diameter of a bubble and the bubble volume fraction inherent in mercury can be decided if the critical pressure, the sound velocity, and resonance frequency is successfully measured by static and dynamic experiment.
Taniguchi, Masaki; Hanada, Masaya; Iga, Takashi*; Inoue, Takashi; Kashiwagi, Mieko; Morishita, Takatoshi; Okumura, Yoshikazu; Shimizu, Takashi*; Takayanagi, Tomohiro*; Watanabe, Kazuhiro; et al.
Proceedings of 19th IAEA Fusion Energy Conference (FEC 2002) (CD-ROM), 5 Pages, 2002/10
A high power neutral beam injector (NBI) has been designed for ITER. A key component of the NBI system is a high power beam source which produces a 40A D
ion beams at the energy of 1 MeV. JAERI has developed a vacuum insulated beam source (VIBS). The VIBS insulates the high voltage of 1 MV by immersing the ion source and accelerator in vacuum. So far the VIBS succeeded in acceleration of 37 mA (power supply drain current) beam up to 970 keV for 1 s. The achieved beam energy is nearly equal to the required value for the ITER NBI system. The negative ion source for the ITER beam source has been also developed. One of the key issues for the negative ion source is reduction of the operating pressure. By optimizing the filter magnetic field for negative ion production even at low pressure, a H ion beam of 31 mA/cm
was extracted at 0.1 Pa. Although the pulse length was very short (0.1 s) the ITER requirement on the current density was demonstrated at 1/3 of the ITER design pressure (0.3 Pa), which could reduce the heat loading on the accelerator grids.
Hanada, Masaya; Kashiwagi, Mieko; Morishita, Takatoshi; Taniguchi, Masaki; Okumura, Yoshikazu; Takayanagi, Tomohiro; Watanabe, Kazuhiro
Fusion Engineering and Design, 56-57, p.505 - 509, 2001/10
Times Cited Count：20 Percentile：78.30(Nuclear Science & Technology)no abstracts in English
Miyamoto, Naoki*; ; Okumura, Yoshikazu; Inoue, Takashi; Fujiwara, Yukio; Miyamoto, Kenji; Nagase, Akihito*; Ohara, Yoshihiro; Watanabe, Kazuhiro
AIP Conference Proceedings 380, p.300 - 308, 1996/00
no abstracts in English
ion sourceOkumura, Yoshikazu; Hanada, Masaya; Inoue, Takashi; Mizuno, Makoto; Ohara, Yoshihiro; Pamela, J.*; Suzuki, Yasuo*; Tanaka, Hideki*; Watanabe, Kazuhiro
Production and Application of Light Negative Ions, p.35 - 40, 1991/00
no abstracts in English
additionIkezoe, Yasumasa; ; Shimizu, Saburo; Nakajima, Hayato; ;
Radiation Physics and Chemistry, 26(4), p.445 - 449, 1985/00
no abstracts in English
Yoshimura, Kazuo; Ikeda, Makinori; Enuma, Yasuhiro; Aizawa, Kosuke
no journal, ,
JAEA has conducted a safety evaluation of impacts of double leakage at the PHTSs considering the passive safety features of Monju as the best-estimate evaluation for a DEC. The result shows that the total amount of leaked sodium can be reduced by the depressurization of the cover gas resulting from decrease in coolant inventory, i.e. negative pressure effects. The reactor coolant level required for decay heat removal, therefore, can be maintained even under double leakage at the PHTSs.
