Analysis of deposits inside "X-6 penetration" for the Unit 2 primary containment vessel at Fukushima Daiichi Nuclear Power Station

Yoneyama, Kai; Nitta, Ayako; Tanaka, Yasuyuki; Kodaka, Noriyasu; Kikuchi, Riku; Sakano, Takuma; Furuse, Takahiro; Sato, Soichi; Sambongi, Mitsuru; Tanaka, Kosuke

JAEA-Technology 2025-008, 44 Pages, 2025/12

JAEA-Technology-2025-008.pdf:4.3MB

At the TEPCO's Fukushima Daiichi Nuclear Power Station (1F), an investigation inside the reactors has been carried out. In order to safely carry out the decommissioning work such as fuel debris retrieval and building demolition, it is important to estimate the contamination in primary containment vessel for control the decommissioning planning and the worker radiation exposure levels. Therefore, the analysis of the deposit inside the penetration for the 1F Unit 2 primary containment vessel ("X-6 penetration") was performed to clarify the components and activity. The smears from the deposit were used for the analysis. Non-destructive analysis such as gamma-ray spectrometry, X-ray Fluorescence (XRF) and Scanning Electron Microscope-Energy dispersive X-ray spectroscopy (SEM-EDX) for the smear-samples were performed to determine the gamma-nuclides and the morphology of elements in the deposit. Furthermore, in order to evaluate the nuclides and nuclide composition of the deposit in detail, the smear-samples were dissolved and the quantitative analysis of gamma-nuclides, Sr-90, alpha-nuclides in the dissolved solution were conducted. The results (nondestructive analysis and quantitative analysis) were compared with the results of samples collected at different locations in the X-6 penetration in 2020. In the gamma-ray spectrometry as non-destructive analysis where the smears were analyzed directly, Co- 60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155 and Am-241 were detected. In XRF results, Fe originating from construction material was detected as a major element and small amount of U and Zr originating from the fuel and fuel cladding were also detected. In SEM-EDX results, O and Fe were found as a major element of the deposit and U particles coexisting with Fe, Si, Cr, Ni and Zr were also found. These results were consistent with the SEM-EDX results of the samples collected in 2020. In radioactivity analysis, quantitative values for gamma-nuclides (Co-60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155), Sr-90, Pu-238, Pu-239+240, Am-241, Cm-244, U-235 and U-238 were obtained. Using the results, the ratios of radioactivity based on Cs-137 and U-238 were calculated. Both sets of the ratios were compared to the calculated value of the Unit 2 fuel composition from ORIGEN.

Applicability of uncertainty quantification and sensitivity analysis for validation of fast reactor plant dynamics analysis code

Hamase, Erina; Kawamura, Takumi*; Doda, Norihiro; Tanaka, Masaaki

Nihon Kikai Gakkai 2025-Nendo Nenji Taikai Koen Rombunshu (Internet), 5 Pages, 2025/09

To investigate the applicability of uncertainty quantification (UQ) and sensitivity analysis (SA) methods for validating a fast reactor plant dynamics analysis code, forward UQ and SA employing Sobol' method were performed for FFTF LOFWOS test No.13. The result demonstrated that validity can be judged if the test results fall within the quantified uncertainty range, and that the dominant input parameters influencing uncertainty can be quantitatively evaluated, enabling prioritization of parameters for uncertainty reduction. This confirms the applicability of forward UQ and SA employing Sobol' method.

Structural behaviors of lead zirconate titanate-based ferroelectric ceramics during pyroelectric-power generation cycles

Kawasaki, Takuro; Fukuda, Tatsuo; Yamanaka, Satoru*; Murayama, Ichiro*; Kato, Takanori*; Baba, Masaaki*; Hashimoto, Hideki*; Harjo, S.; Aizawa, Kazuya; Tanaka, Hirohisa*; et al.

Journal of Applied Physics, 137(9), p.094101_1 - 094101_7, 2025/03

https://doi.org/10.1063/5.0243081

Application of diffusive gradients in thin films (DGT) for the dynamic speciation of radioactive cesium in Fukushima Prefecture, Japan

Tanaka, Takuro*; Fukuoka, Masafumi*; Toda, Kanako*; Nakanishi, Takahiro; Terashima, Motoki; Fujiwara, Kenso; Niwano, Yuma*; Kato, Hiroaki*; Kobayashi, Natsuko*; Tanoi, Keitaro*; et al.

ACS ES&T Water (Internet), 4(8), p.3579 - 3586, 2024/08

https://doi.org/10.1021/acsestwater.4c00453

U(VI) sorption on illite in the presence of carbonate studied by cryogenic time-resolved laser fluorescence spectroscopy and parallel factor analysis

Mei, H.; Aoyagi, Noboru; Saito, Takumi*; Tanaka, Kazuya; Sugiura, Yuki; Tachi, Yukio

Applied Geochemistry, 162, p.105926_1 - 105926_8, 2024/02

https://doi.org/10.1016/j.apgeochem.2024.105926

Site-specific relaxation of peptide bond planarity induced by electrically attracted proton/deuteron observed by neutron crystallography

Chiba, Kaori*; Matsui, Takuro*; Chatake, Toshiyuki*; Ohara, Takashi; Tanaka, Ichiro*; Yutani, Katsuhide*; Niimura, Nobuo*

Protein Science, 32(10), p.e4765_1 - e4765_13, 2023/10

https://doi.org/10.1002/pro.4765

Probing strain and doping along a graphene wrinkle using tip-enhanced Raman spectroscopy

Balois-Oguchi, M. V.*; Hayazawa, Norihiko*; Yasuda, Satoshi; Ikeda, Katsuyoshi*; Nguyen, T. Q.*; Escao, M. C.*; Tanaka, Takuo*

Journal of Physical Chemistry C, 127(12), p.5982 - 5990, 2023/03

https://doi.org/10.1021/acs.jpcc.2c08529

Micrometer-sized wrinkles in graphene are known to affect the electronic properties of graphene due to their shape and the strain variations they create. Here, we analyze the strain distribution and doping of a graphene wrinkle having 1.9 nm width using tip-enhanced Raman spectroscopy (TERS) in ambient conditions. We found a strong correlation between the TERS images of the graphene wrinkle and the electronic Raman scattering (eRS) of the Au(111) substrate. Our work demonstrates that the as-fabricated physical and electronic properties of nanometer-sized features, such as wrinkles, can be probed and studied in detail with TERS which is essential for nanodevice characterization.

Stable C and N isotope abundances in water-extractable organic matter from air-dried soils as potential indices of microbially utilized organic matter

Nagano, Hirohiko*; Atarashi-Andoh, Mariko; Tanaka, Sota*; Yomogida, Takumi; Kozai, Naofumi; Koarashi, Jun

Frontiers in Forests and Global Change (Internet), 6, p.1228053_1 - 1228053_9, 2023/00

https://doi.org/10.3389/ffgc.2023.1228053

Benchmark analysis of FFTF Loss of Flow Without Scram Test No.13 using fast reactor plant dynamics analysis code Super-COPD

Hamase, Erina; Ohgama, Kazuya; Kawamura, Takumi*; Doda, Norihiro; Yamano, Hidemasa; Tanaka, Masaaki

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 9 Pages, 2022/10

To improve the prediction accuracy of the plant dynamics analysis code named Super-COPD, JAEA has joined the IAEA benchmark for the FFTF Loss of Flow Without Scram Test No.13. In the first blind phase, there was the challenge to perform outlet temperatures of fuel assemblies more accurately. Hence, the renewed analysis was performed with the whole core multi-channel model in which each assembly was modelled to simulate the radial heat transfer among assemblies and the flow redistribution induced by the buoyancy in the NC conditions. Then, to validate the coupled transient analysis between the whole core multi-channel model and the one-point kinetics model, the analysis considering major reactivity feedbacks such as GEM, assembly bowing was performed. As a result, the second peak of outlet temperatures was reproduced successfully, and it was observed that the plant dynamics analysis could follow the measured data.

Uranium chelating ability of decorporation agents in serum evaluated by X-ray absorption spectroscopy

Uehara, Akihiro*; Matsumura, Daiju; Tsuji, Takuya; Yakumaru, Haruko*; Tanaka, Izumi*; Shiro, Ayumi*; Saito, Hiroyuki*; Ishihara, Hiroshi*; Homma-Takeda, Shino*

Analytical Methods, 14(24), p.2439 - 2445, 2022/06

https://doi.org/10.1039/D2AY00565D