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Kamikawa, Yutaka; Suzuki, Makoto; Agake, Toshiki; Murakami, Takahiko; Morita, Yusuke; Shiina, Hidenori; Fukushima, Manabu; Hirane, Nobuhiko; Ouchi, Yasuhiro
JAEA-Technology 2023-030, 57 Pages, 2024/03
Owing to the publication of the latest data about aircraft crashes by Nuclear Regulation Authority (NRA), it was necessary to re-evaluate the probabilities of aircraft crashes for Nuclear Science Research Institute (NSRI). By using of the assessment method provided in "Regulatory Guide of the Assessment Standard for Probability of Airplane Crash on a Nuclear Power Reactor Facility", we re-evaluated the probabilities of aircraft crashes against the nuclear facilities in NSRI. As a result of the evaluations, the sum of the probabilities of aircraft crashes against Waste Treatment Facilities (maximum probability among all nuclear facilities in NSRI) is 5.6810
(times/(reactor
year)) which is lower than 10
(times/(reactor
year)) that is the assessment criterion whether aircraft crashes is considered to be "anticipated external human induced events" in design basis or not.
Araki, Shohei; Gunji, Satoshi; Arakaki, Yu; Yoshikawa, Tomoki; Murakami, Takahiko; Kobayashi, Fuyumi; Izawa, Kazuhiko; Suyama, Kenya
Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 8 Pages, 2023/10
New experiments simulating fuel debris in the new criticality assembly, STACY, are designed to contribute to the validation of criticality calculations for criticality control of the fuel debris in the Fukushima Daiichi Nuclear Power Plant accident. In the new STACY experiment, a two-region core consisting of a driver region and a test region was investigated in order to configure a debris-simulated core with under-moderation condition (lattice pitch 1.27-cm) having the constraint of available fuel rod number. The test region with a 1.27-cm lattice pitch is surrounded by the driver region, in which fuel rods are arranged in a checkerboard pattern on a 1.27-cm lattice plate, with a 1.80-cm lattice pitch. Neutron spectra and sensitivity were calculated by using MCNP6 and ENDF/B-VII. The core which has a 1717 test region with 373 fuel rods is the largest two-region core under the constraint. It was found that the core which has a 17
17 test region can simulate the neutron spectra of under-moderation condition in a 13
13 region inside the test region with the root-mean square percentage error of less than 5%. It was also confirmed that the sensitivity of
Si and
Ca (n,
) reactions when the concrete simulant, was loaded could be simulated.
Araki, Shohei; Gunji, Satoshi; Arakaki, Yu; Murakami, Takahiko; Yoshikawa, Tomoki; Hasegawa, Kenta; Tada, Yuta; Izawa, Kazuhiko; Suyama, Kenya
Proceedings of 4th Reactor Physics Asia Conference (RPHA2023) (Internet), 4 Pages, 2023/10
To conduct integrated thermal power measurements for the performance test of the modified STACY, we re-analyzed the experimental data measured in the solution fuel STACY using the activation method. We validated its feasibility under the limited number of activation detectors. The re-analyzed results of the activation method by using MVP and PHITS with JENDL-4.0 indicated that the effect of the difference of the position between activation detectors was small enough, and the results agreed with that of the fission product analysis within almost 10%. It is conceivable that the activation method could be adopted instead of the fission product analysis.
Ishii, Kenji; Hoesch, M.*; Inami, Toshiya; Kuzushita, Kaori*; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Mizuki, Junichiro; Endo, Yasuo; Tsutsui, Kenji*; et al.
Journal of Physics and Chemistry of Solids, 69(12), p.3118 - 3124, 2008/12
Times Cited Count:3 Percentile:17.86(Chemistry, Multidisciplinary)Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.
AIP Conference Proceedings 850, p.445 - 446, 2006/09
Mott gap excitations in the optimally doped high- superconductor YBa
Cu
O
(
= 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the
-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the
direction, while the excitation from the CuO
plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO
plane site.
Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.
Physical Review Letters, 94(18), p.187002_1 - 187002_4, 2005/05
Times Cited Count:40 Percentile:80.46(Physics, Multidisciplinary)Mott gap excitations in the optimally doped high- superconductor YBa
Cu
O
(
= 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the
-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the
direction, while the excitation from the CuO
plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO
plane site.
Maekawa, Tomoyuki; Seki, Masakazu; Sumiya, Masato; Araki, Shohei; Murakami, Takahiko; Hasegawa, Kenta; Yoshikawa, Tomoki; Mori, Takashi*; Ishii, Junichi; Kobayashi, Fuyumi; et al.
no journal, ,
As previously reported, to clarify critical characteristics of fuel debris, the Static Experiment Critical Facility (STACY) is being converted to the heterogenous thermal system using fuel rods and light water moderator from the homogenous system using solution fuel. Seismic reinforcement of the support structure of the core tank started in 2022. This report presents progress on manufacture and construction of the modified STACY in 2021 and 2022.
Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori*; Hoesch, M.; Tsubota, Masami; Mizuki, Junichiro; et al.
no journal, ,
Resonant inelastic X-ray scattering studies on high- superconductors Nd
Ce
CuO
and YBa
Cu
O
are presented. In Nd
CuO
and YBa
Cu
O
, which are Mott insulators, an excitation across the Mott gap is observed around 2 eV. The spectral weight of this excitation shifts to higher energy with increasing the momentum transfer and the dispersion of the excitation is larger along the
direction than the
direction. An intraband excitation in the upper Hubbard band emerges in the spectra of electron-doped Nd
Ce
CuO
. As a function of the momentum transfer in the CuO
plane, the excitation shifts to higher energy up to 2-2.5 eV at the zone boundary, accompanied by an increase of the spectral width. On the other hand, excitations from two inequivalent Cu sites in hole-doped YBa
Cu
O
are distinguished by the momentum dependence and the Mott gap of the CuO chain site is found to be much smaller than that of the CuO
plane site.
Araki, Shohei; Murakami, Takahiko; Kamikawa, Yutaka; Arakaki, Yu; Tada, Yuta; Aizawa, Eiju; Ishii, Junichi; Seki, Masakazu; Izawa, Kazuhiko; Gunji, Satoshi
no journal, ,
We conducted thermal power measurements and thermal power calibration for a performance test in the modified STACY. The activation method was adopted in the thermal power measurements. The core for the measurements consisted of 253 fuel rods and a sample driver. The gold foils used for the activation foil method were installed in the sample driver. The operation was carried out twice, at 20-W and 50-W. The neutron flux in the core and the response of the gold foil were calculated using MVP and PHITS, respectively, with JENDL-5 as the nuclear data. In each measurement, the integrated power was 4.2-Wh and 8.9-Wh, respectively. The indicated power with default setting was found to be about 50% higher than the evaluated value.
Hasegawa, Kenta; Arakaki, Yu; Murakami, Takahiko; Sumiya, Masato; Aizawa, Eiju; Seki, Masakazu; Ishii, Junichi; Araki, Shohei; Izawa, Kazuhiko; Gunji, Satoshi
no journal, ,
no abstracts in English
Araki, Shohei; Arakaki, Yu; Maekawa, Tomoyuki; Murakami, Takahiko; Hasegawa, Kenta; Yoshikawa, Tomoki; Tada, Yuta; Kamikawa, Yutaka; Sumiya, Masato; Seki, Masakazu; et al.
no journal, ,
In the TEPCO's Fukushima Daiichi Nuclear Power Plant accident, fuel debris was formed by fuel melting and mixing with in-core structures. Although the detailed properties of the fuel debris are still unknown, it is thought to contain materials such as iron and concrete. Then, in order to understand the criticality characteristics of fuel debris, JAEA is conducting a comprehensive numerical analysis assuming the composition of fuel debris containing concrete and iron. However, integral experimental data including these materials are scarce, and the validation of the analytical results has not been fully investigated. Thus, JAEA modified the criticality facility STACY in order to obtain experimental data that will contribute to the validation. This report describes the outline and status of the modified-STACY, and the plan is also presented.