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Shiba, Shigeki*; Iwahashi, Daiki*; Okawa, Tsuyoshi*; Gunji, Satoshi; Izawa, Kazuhiko; Suyama, Kenya
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05
The Nuclear Regulation Authority (NRA) has tackled the experimental approach for determining the criticality of pseudo-fuel debris plausibly simulating actual fuel debris since 2014, collaborating with the Japan Atomic Energy Agency. To elucidate the characteristics of the pseudo-fuel debris, the Japan Atomic Energy Agency modified the STACY (STAtic experiment Critical facilitY) to conduct critical experiments simulating fuel debris. Thus, we proposed three types of modified STACY core configurations. In critical experiments in the modified STACY core, it is important to judge whether the proposed modified STACY core configurations are representative of molten core-concrete interaction debris or not. In this study, we built pseudo-fuel debris models considering a volume ratio of pseudo-fuel debris to moderation (V
/V
) and calculated uncertainty-based similarity values (C
) between the modified STACY core configurations and pseudo-fuel debris models using Tools for Sensitivity and Uncertainty Analysis Methodology Implementation-Indices and Parameters (TSUNAMI-IP) in SCALE 6.2. Consequently, the modified STACY core configuration loading structure rods we proposed completely resulted in high similarity to the pseudo-fuel debris models through V
/V
values. The main contributions to C values were 
U 
, U 
, and 
Fe (n,
), except for the pseudo-fuel debris model, including extremely high concrete components.
Washiya, Tadahiro
no journal, ,
no abstracts in English
(Zr,U)Hoshino, Takanori; Ikeuchi, Hirotomo; Suzuki, Seiya; Okamura, Nobuo; Watanabe, Masayuki; Koizumi, Kenji
no journal, ,
no abstracts in English
Morimoto, Kyoichi; Hirooka, Shun; Akashi, Masatoshi; Watanabe, Masashi; Komeno, Akira; Ogasawara, Masahiro*
no journal, ,
The influence of Gd on these characteristics is important for the prediction because subassemblies of Gd-bearing uranium oxide fuels were loaded in the some reactor cores of Fukushima Daiichi Nuclear Power Plant. Additionally, it is important to comprehend the placement of Gd in the debris from the view point of the re-criticality by relocation of the debris during removing the debris. In this study, U, Gd and Zr mixed oxide specimens were fabricated by the conventional powder metallurgy process and these specimens were melted and solidified to prepare simulated corium debris bearing Gd (sim-debris). Melting point and thermal conductivities of sim-debris were measured. X-ray diffraction analysis and electron probe microanalysis were conducted to evaluate the phase states.
Nishina, Masahiro; Hirooka, Shun; Morimoto, Kyoichi
no journal, ,
no abstracts in English
Ogino, Hideki; Yano, Kimihiko; Takano, Masahide; Washiya, Tadahiro; Miyamoto, Yasuaki; Kawano, Shohei*
no journal, ,
no abstracts in English
Tominaga, Aki; Shobu, Takahisa; Satou, Yukihiko; Shiro, Ayumi*; Kuwatsuru, Osamu*; Uno, Masayoshi*
no journal, ,
During the fracture test of the simulated debris, the internal deformation and the strain were evaluated by X-ray CT and X-ray diffraction using synchrotron radiation source, respectively. The purpose of this study is to determine the fracture strength of the debris, the prediction of which is thought to be difficult, from the CT images and strain amounts during the fracture test. We'll report the results of measurements using synchrotron X-ray CT and diffraction at the JAEA beamline BL22XU on SPring-8. ZrO phase, AlO
phase, and voids were observed in the CT image. In the strain analysis by X-ray diffraction of this sample was obtained from the average strain of the sample flat plate with the thickness of about 0.1 mm including the center of the sample. We consider that the difference between the macrostrain and microstrain is the amount of void deformation.
Tominaga, Aki; Shobu, Takahisa; Satou, Yukihiko; Tsuji, Takuya; Matsumura, Daiju; Shiro, Ayumi*; Kuwatsuru, Osamu*; Uno, Masayoshi*
no journal, ,
We focused on element selectivity, which is a feature of the imaging method and the XAFS method. The research purpose is to construct the CT-XAFS method on BL22XU. We have constructed a system that enables energy scanning near the absorption edge of target elements. In the measurement, we identified the scan energies containing many target elements. Based on the results, we built a technology to obtain information on the crystal structure and valence. The simulated debris of the measurement sample was made by melting and solidifying UO and BO at 1800
C using eutectic reaction. Simulated fuel debris was irradiated with synchrotron radiation, and its interior was observed using the X-ray CT method. After confirming the inside, a CT image was acquired at the energy around the U-L
edge. In the presentation, we will report on the construction status of the measurement technology, the acquisition of XAFS spectra at specific locations inside the material from CT images, and the presence or absence of structural differences due to differences in fabrication methods.