A Coupled modeling simulator for near-field processes in cement engineered barrier systems for radioactive waste disposal

Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira

Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09

https://doi.org/10.3390/cryst10090767

Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.

Suppression of radiation-induced point defects by rhenium and osmium interstitials in tungsten

Suzudo, Tomoaki; Hasegawa, Akira*

Scientific Reports (Internet), 6, p.36738_1 - 36738_6, 2016/11

https://doi.org/10.1038/srep36738

Modeling of the evolution of radiation-induced defects is important for finding radiation-resistant materials, which would be greatly appreciated in nuclear applications. We apply the first principles method combined with kinetic Monte Carlo to indicate a mechanism to mitigate the effect of radiation by adding particular solute elements that change the migration dimension of interstitials in W crystals. The resultant mechanism is applicable to any body-centered-cubic (BCC) metals whose SIAs have one-dimensional (1D) motion and is expected to provide a general guideline for computational design of radiation-resistant alloys in the field of nuclear applications.

Atomistic and continuum comparative studies on the stress distribution around a nano-crack on the grain boundary for modeling hydrogen embrittlement of iron

Ebihara, Kenichi; Kaburaki, Hideo; Itakura, Mitsuhiro

"Hagane No Kikaiteki Tokusei Ni Oyobosu Suiso No Koka To Sono Hyoka" Shimpojium Yokoshu (USB Flash Drive), 6 Pages, 2014/09

Since hydrogen(H) embrittlement is one factor causing degradation and/or fracture of steel, understanding its mechanism is required. The grain-boundary(GB) decohesion due to segregation of H is considered to cause the delayed fracture of high strength steels and the cold cracking in welding. In the model based on GB decohesion, information of strength of GBs estimated in the atomic scale is used for the estimation of strength or crack propagation in the macroscopic scale. However the modeling between the atomic and the macroscopic scales is not clear. In particular, the validity of the model using the elastic continuum around nano-cracks for stress concentration at the crack tip is not clear. Thus, we examined the difference of the stress distribution around the nano-crack which was estimated by molecular dynamics and by a continuum calculation. As a result, the discrepancy became remarkable at high strain. The stress concentration was not simulated by the elastic continuum model.

Quantitative modeling of photoassimilate flow in an intact plant using the Positron Emitting Tracer Imaging System (PETIS)

Matsuhashi, Shimpei; Fujimaki, Shu; Kawachi, Naoki; Sakamoto, Koichi; Ishioka, Noriko; Kume, Tamikazu

Soil Science and Plant Nutrition, 51(3), p.417 - 423, 2005/06

https://doi.org/10.1111/j.1747-0765.2005.tb00047.x

no abstracts in English

Meeting report of internatinal tokamak physics activity, 12

Sakamoto, Yoshiteru; Toi, Kazuo*; Fukuda, Takeshi*; Fukuyama, Atsushi*; Fujita, Takaaki; Ogawa, Yuichi*; Takizuka, Tomonori; Miura, Yukitoshi; Yagi, Masatoshi*; Yamada, Hiroshi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 80(8), P. 678, 2004/08

no abstracts in English

Solid-solution reactions in As(V) sorption by schwertmannite

Fukushi, Keisuke*; Sato, Tsutomu*; Yanase, Nobuyuki

Environmental Science & Technology, 37(16), p.3581 - 3586, 2003/07

https://doi.org/10.1021/es026427i

The mechanism of As(V) sorption on schwertmannite was investigated by a batch sorption experiment as a function of solution As(V) concentration under acidic conditions (pH 3.3 0.1) at 25 C. The reacted solution chemistry and mineralogy showed that the mechanism of As(V) sorption was ligand exchange with solid phase SO in schwertmannite. Two processes presumably occur simultaneously within the reaction period. i.e., ligand exchange of As(V) with surface site SO and subsequent transfer of As(V) to the structure and ligand exchange with tunnel site SO. The exchange ratio between As(V) sorption and SO release, and the SO coordination environment in schwertmannite indicates that monodentate As(V) coordination occurs in surface sites while bidentate binuclear As(V) coordination occurs in tunnel sites. Sorption modeling that considers the different types of reactive sites successfully described the observed As(V) sorption behavior.

ITPA (International Tokamak Physics Activity) meeting report, 6

Ide, Shunsuke; Fukuda, Takeshi; Miura, Yukitoshi

Purazuma, Kaku Yugo Gakkai-Shi, 79(2), P. 194, 2003/02

no abstracts in English

JACOS AI-based simulation system for man-machine system behavior in NPP

Yoshida, Kazuo; Yokobayashi, Masao; Tanabe, Fumiya; Kawase, Katsumi*; Komiya, Akitoshi*

JAERI-Data/Code 2001-023, 118 Pages, 2001/08

JAERI-Data-Code-2001-023.pdf:8.65MB

no abstracts in English

"Local solid element modeling" for detailed analyses of floor liner

Tsukimori, Kazuyuki

JNC TN9400 2000-086, 103 Pages, 2000/08

JNC-TN9400-2000-086.pdf:3.67MB

ln order to evaluate the integrity of the floor liner of "MONJU" at sodium leakage accident, nonlinear finite element analyses have been conducted considering the effect of thinning of the liner due to molten salt type corrosion. Modeling by shell elements is appropriate since liner is composed of thin plates, however, it is difficult to deal with the very local strain behaviors. 0n the other hand, modeling by solid elements makes the numerical calculation impractical. If we extract the small part of the liner which includes local discontinuities, it is possible to evaluate local strain behaviors practically by using the solid element analysis model of the part. To realize this approach, the method to generate all the boundary displacements of the part model from the shell element analysis result of total structure is needed. The aims of this study are to develop the method to deal with the incompatibility between shell and solid elements at part model boundary, and to build numerical analysis circumstances including this method to make the detailed nonlinear finite element analyses of the floor liner of "MONJU" possible. Summary of the results is shown below, (1)The problem of the incompatibility between shell and solid elements was solved by introducing weighting function at 'T' and 'L' type corners and the interpolation function of 4-node rectangular plate bending element at the connection between liner plate and frame. (2)Software system was developed by using 'FINAS' and verified. (3)This approach was applied to one of the cases of the floor liner analyses of "MONJU" at sodium leakage accident. The analysis result showed that three-dimensional local strain behavior could be evaluated directly. ln addition, it was confirmed that the result by shell element analysis was conservative in evaluation of strain compared with that by solid element analysis in this case.

A feasibility study of the particle interaction method for the flow regimes with the chemical reaction; (Report under the contract between JNC and Toshiba Corporation)

Shirakawa, Noriyuki*; *; *; *

JNC TJ9440 2000-008, 47 Pages, 2000/03

JNC-TJ9440-2000-008.pdf:1.96MB

The numerical thermohydraulic analysis of a LMFR component should involve its whole boundaly in order to evaluate the effect of chemical reaction within it. Therefore, it becomes difficult mainly due to computing time to adopt microscopic approach for the chemical reaction directly. Thus, the thermohydraulic code is required to model the chemically reactive fluid dynamics with constitutive correlations. The reaction rate denpends on the binary contact areas between components such as continuous liquids, droplets, solid particles, and bubbles. The contact areas change sharply according to the interface state between components. Since no experiments to study the jet flow with sodium-water chemical reaction have been done, the goal of this study is to obtain the knowledge of flow regimes and contact areas by analyzing the fluid dynamics of multi-pahse and reactive components mechanistically with the particle interaction method. For the first stage of the study, the applicability of this method to the nalysis of a liquid jet into the other liquid pool was investigated. Based on the literatures, we investigated the jet flow mechanisms and analyzed the experiment of a water jet into a gasoline pool. We also analyzed SWAT3/Run19 test, the jet flow in a rod bundle, to study the applicability of the method to a complicated boundary without a chemical reaction model. The calculated fluid dynamics was in good agreement with the experiment. Furthermore, we studied and formulated the paths of phase change and chemical reaction, and conceptually designed the adopting the heat-transfer-limited phase change model and the synthesizd reaction model with a water-hydrogen conversion ratio.