A Raman spectroscopy study of bicarbonate effects on UO

McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kimuro, Shingo; Ishidera, Takamitsu

Journal of Nuclear Science and Technology, 60(12), p.1586 - 1594, 2023/12

https://doi.org/10.1080/00223131.2023.2236104

Optimization of dissolved hydrogen concentration for mitigating corrosive conditions of pressurised water reactor primary coolant under irradiation, 2; Evaluation of electrochemical corrosion potential

Hata, Kuniki; Hanawa, Satoshi; Chimi, Yasuhiro; Uchida, Shunsuke; Lister, D. H.*

Journal of Nuclear Science and Technology, 60(8), p.867 - 880, 2023/08

https://doi.org/10.1080/00223131.2022.2127955

One of the major subjects for evaluating the corrosive conditions in the PWR primary coolant was to determine the optimal hydrogen concentration for mitigating PWSCC without any adverse effects on major structural materials. As suitable procedures for evaluating the corrosive conditions in PWR primary coolant, a couple of procedures, i.e., water radiolysis and ECP analyses, were proposed. The previous article showed the radiolysis calculation in the PWR primary coolant, which was followed by an ECP study here. The ECP analysis, a couple of a mixed potential model and an oxide layer growth model, was developed originally for BWR conditions, which was extended to PWR conditions with adding Li (Na) and H effects on the anodic polarization curves. As a result of comparison of the calculated results with INCA in-pile-loop experiment data as well as other experimental data, it was confirmed that the ECPs calculated with the coupled analyses agreed with the measured within 100mV discrepancies.

Local electronic structure of interstitial hydrogen in MgH inferred from muon study

Kadono, Ryosuke*; Hiraishi, Masatoshi*; Okabe, Hirotaka*; Koda, Akihiro*; Ito, Takashi

Journal of Physics; Condensed Matter, 35(28), p.285503_1 - 285503_13, 2023/07

https://doi.org/10.1088/1361-648X/acccc7

Angular distribution of rays from a neutron-induced -wave resonance of Xe

Okudaira, Takuya*; Tani, Yuika*; Endo, Shunsuke; Doskow, J.*; Fujioka, Hiroyuki*; Hirota, Katsuya*; Kameda, Kento*; Kimura, Atsushi; Kitaguchi, Masaaki*; Luxnat, M.*; et al.

Physical Review C, 107(5), p.054602_1 - 054602_7, 2023/05

https://doi.org/10.1103/PhysRevC.107.054602

no abstracts in English

Oxygen potential, oxygen diffusion, and defect equilibria in UO

Watanabe, Masashi; Kato, Masato

Frontiers in Nuclear Engineering (Internet), 1, p.1082324_1 - 1082324_9, 2023/01

https://doi.org/10.3389/fnuen.2022.1082324

Since the oxygen potential and the oxygen coefficient of UO have a significant impact on fuel performance, many experimental data have been obtained. However, experimental data of the oxygen potential and the oxygen diffusion coefficient in the high temperature region above 1673 K are very limited. In the present study, we aimed to obtain these data and analyze them by defect chemistry. The oxygen potentials and the oxygen chemical diffusion coefficient of UO were measured by the gas equilibrium method in the near stoichiometric region at temperatures ranging from 1673 to 1873 K. A data set of oxygen potentials was made together with literature data and analyzed by defect chemistry. The oxygen potential of UO was determined as a function of O/U ratio and temperature, and an equation representing the relationship was derived. The oxygen chemical diffusion coefficient values obtained in this study were reasonably close to the literature values. The oxygen partial pressure dependence of the oxygen chemical diffusion coefficients was predicted from the evaluated results of the oxygen potential data, but no clear dependence was observed.

Recent studies on fuel properties and irradiation behaviors of Am/Np-bearing MOX

Hirooka, Shun; Yokoyama, Keisuke; Kato, Masato

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 8 Pages, 2022/04

Property studies on Am/Np-bearing MOX were carried out and how the properties influences on the irradiation behaviors was discussed. Both Am and Np inclusions increase the oxygen potential of MOX. Inter-diffusion coefficients obtained by using diffusion couple technique indicate that the inter-diffusion coefficient is larger in the order of U-Am, U-Pu and U-Np. Also, the inter-diffusion coefficients were evaluated to be larger at the O/M = 2 than those of O/M 2 by several orders. The increase of oxygen potential with Am/Np leads to higher vapor pressure of UO and the acceleration of the pore migration along temperature gradient during irradiation. The redistributions of actinide elements were also considered with the relationship of the pore migration and diffusion in solid state. Thus, the obtained inter-diffusion coefficients directly influence on the redistribution rate. The obtained properties were modelled and can be installed in a fuel irradiation simulation code.

Development of an analysis method for electrochemical corrosion potential in PWR primary coolant under irradiation

Hata, Kuniki; Uchida, Shunsuke; Hanawa, Satoshi; Chimi, Yasuhiro

Proceedings of International Symposium on Contribution of Materials Investigations and Operating Experience to LWRs' Safety, Performance and Reliability (Fontevraud 10) (Internet), 11 Pages, 2022/00

Evolution of the reaction and alteration of mudstone with ordinary Portland cement leachates; Sequential flow experiments and reactive-transport modelling

Bateman, K.; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 11(9), p.1026_1 - 1026_23, 2021/09

https://doi.org/10.3390/min11091026

Data-driven derivation of partial differential equations using neural network model

Koyamada, Koji*; Yu, L.*; Kawamura, Takuma; Konishi, Katsumi*

International Journal of Modeling, Simulation, and Scientific Computing, 12(2), p.2140001_1 - 2140001_19, 2021/04

https://doi.org/10.1142/S1793962321400018

With the improvement of sensors technologies in various fields such as fluid dynamics, meteorology, and space observation, it is an important issue to derive explanatory models using partial differential equations (PDEs) for the big data obtained from them. In this paper, we propose a technique for estimating linear PDEs with higher-order derivatives for spatiotemporally discrete point cloud data. The technique calculates the time and space derivatives from a neural network (NN) trained on the point cloud data, and estimates the derivative term of the PDE using regression analysis techniques. In the experiment, we computed the error of the estimated PDEs for various meta-parameters for the PDEs with exact solutions. As a result, we found that increasing the hierarchy of NNs to match the order of the derivative terms in the exact solution PDEs and adopting L1 regularization with LASSO as the method of regression analysis increased the accuracy of the model.

Voltage drop analysis and leakage suppression design for mineral-insulated cables

Hirota, Noriaki; Shibata, Hiroshi; Takeuchi, Tomoaki; Otsuka, Noriaki; Tsuchiya, Kunihiko

Journal of Nuclear Science and Technology, 57(12), p.1276 - 1286, 2020/12

https://doi.org/10.1080/00223131.2020.1782280

The influence of materials of mineral-insulated (MI) cables on their electrical characteristics upon exposure to high-temperature conditions was examined via a transmission test, in the objective of achieving the stability of the potential distribution along the cable length. Occurrence of a voltage drop along the cable was confirmed for aluminum oxide (AlO) and magnesium oxide (MgO), as insulating materials of the MI cable. A finite-element method (FEM)-based analysis was performed to evaluate the leakage in the potentials, which was found at the terminal end. Voltage drop yields by the transmission test and the analysis were in good agreement for the MI cable of AlO and MgO materials, which suggests the reproducibility of the magnitude relationship of the experimental results via the FEM analysis. To suppress the voltage drop, the same FEM analysis was conducted, the diameter of the core wires () and the distance between them () were varied. Considering the variation of , the potential distribution in the MI cable produced a minimum voltage drop corresponding to a ratio of 0.35, obtained by dividing with that of the insulating material (). In case of varying , a minimum voltage drop was l/ of 0.5.