Numerical simulation on self-leveling behavior of mixed particle beds using multi-fluid model coupled with DEM

Phan, L. H. S.*; Ohara, Yohei*; Kawata, Ryo*; Liu, X.*; Liu, W.*; Morita, Koji*; Guo, L.*; Kamiyama, Kenji; Tagami, Hirotaka

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 12 Pages, 2018/10

Self-leveling behavior of core fuel debris beds is one of the key phenomena for the safety assessment of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). The SIMMER code has been developed for CDA analysis of SFRs, and the code has been successfully applied to numerical simulations for key thermal-hydraulic phenomena involved in CDAs as well as reactor safety assessment. However, in SIMMER's fluid-dynamics model, it is always difficult to represent the strong interactions between solid particles as well as the discrete particle characteristics. To solve this problem, a new method has been developed by combining the multi-fluid model of the SIMMER code with the discrete element method (DEM) for the solid phase to reasonably simulate the particle behaviors as well as the fluid-particle interactions in multi-phase flows. In this study, in order to validate the multi-fluid model of the SIMMER code coupled with DEM, numerical simulations were performed on a series of self-leveling experiments using a gas injection method in cylindrical particle beds. The effects of friction coefficient on the simulation results were investigated by sensitivity analysis. Though more extensive validations are needed, the reasonable agreement between simulation results and corresponding experimental data preliminarily demonstrates the potential ability of the present method in simulating the self-leveling behaviors of debris bed. It is expected that the SIMMER code coupled with DEM is a prospective computational tool for analysis of safety issues related to solid particle debris bed in SFRs.

Experimental study on debris bed characteristics for the sedimentation behavior of solid particles used as simulant debris

Shamsuzzaman, M.*; Horie, Tatsuro*; Fuke, Fusata*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Tagami, Hirotaka; Suzuki, Toru*; Tobita, Yoshiharu

Annals of Nuclear Energy, 111, p.474 - 486, 2018/01

https://doi.org/10.1016/j.anucene.2017.09.011

A Preliminary evaluation of unprotected loss-of-flow accident for a prototype fast-breeder reactor

Suzuki, Toru; Tobita, Yoshiharu; Kawada, Kenichi; Tagami, Hirotaka; Sogabe, Joji; Matsuba, Kenichi; Ito, Kei; Ohshima, Hiroyuki

Nuclear Engineering and Technology, 47(3), p.240 - 252, 2015/04

https://doi.org/10.1016/j.net.2015.03.001

An Investigation on debris bed self-leveling behavior with non-spherical particles

Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Takeda, Shohei*; Nishi, Shimpei*; Nishikido, Tatsuya*; Zhang, B.*; Matsumoto, Tatsuya*; et al.

Journal of Nuclear Science and Technology, 51(9), p.1096 - 1106, 2014/09

AA2013-0303.pdf:1.68MB

https://doi.org/10.1080/00223131.2014.910478

Development of assessment method for a self-leveling behavior of debris bed and analyses of experiments

Tagami, Hirotaka; Cheng, S.; Tobita, Yoshiharu; Guo, L.*; Zhang, B.*; Morita, Koji*

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 8 Pages, 2014/07

https://doi.org/10.1115/ICONE22-30290

The object of this study is to develop new analytical methods to simulate unique phenomena in self-leveling behavior and implement it to SFR safety analysis code. The new methods are developed with assuming that the debris bed behaves as Bingham fluid from this feature. They are categorized into two main parts. The first part is particle interaction models to model the effect of particle-particle collisions. The second part is a large deformation method, which simulates Bingham fluid characteristic of debris bed. An experimental study of self-leveling behavior is analyzed to validate the new methods. The assessment results show that these methods provide a basis to develop analytical methods of self-leveling behavior of debris bed in the safety assessment of SFRs.

Evaluation of debris bed self-leveling behavior; A Simple empirical approach and its validations

Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*

Annals of Nuclear Energy, 63, p.188 - 198, 2014/01

https://doi.org/10.1016/j.anucene.2013.07.050

Application of a large deformation method for self-leveling behavior of a debris bed

Tagami, Hirotaka; Tobita, Yoshiharu

Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 8 Pages, 2012/12

When fuel melt occurs and it interacts with coolant in severe accidents in SFRs, it is solidified and fragmented to particles called as debris. The debris sediments and forms debris beds on structure surface. It is important to confirm whether its thickness exceeds the coolable limit to evaluate the coolability. On the other hand, because a self-leveling behavior relocates the debris and changes the bed thickness, the behavior also must be evaluated at the same time. However, no computer code to simulate this behavior exists. Therefore, this study aims at the development of computer code to simulate the self-leveling behavior on the SIMMER code. The development consists of two necessary steps. About the first step, a macroscopic model developed for fluidized bed is applied. For the second step, large deformation method is modified to be capable in multi-phase flow model. The developed code succeeded in reproducing two experiments relating to self-leveling behavior.

Numerical simulation of the self-leveling phenomenon by modified SIMMER-III

Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*; Yamano, Hidemasa; Tagami, Hirotaka; Suzuki, Toru; Tobita, Yoshiharu

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 10 Pages, 2012/07

During a hypothetical core-disruptive accident in a sodium-cooled FBR, degraded core material can form debris beds on the core-support structure and/or in the lower inlet plenum of the reactor vessel. Heat convection and vaporization of the sodium will lead ultimately to leveling the debris bed that is of crucial importance to the relocation of the molten core, the recriticality evaluation and the heat removal capability of the debris bed. There is, therefore, a great need for more studies focusing on this topic, especially the much needed numerical simulation. The debris fluidization model and the boiling regulation model are proposed and introduced into SIMMER-III. Calculations, by the modified SIMMER-III, against several representative experiments with typical self-leveling behavior have been performed and compared with the evaluated items recorded in experiments. The good agreements on these items suggest the modified SIMMER-III can simulate the self-leveling behavior with reasonable precision, especially on the onset of self-leveling, although further model improvement is necessary to represent the transient behavior of bed leveling more reasonably.

Study on characteristics of particle-bed self-leveling driven by gas injection

Nakamura, Yuya*; Gondai, Yoji*; Cheng, S.*; Takeda, Shohei*; Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*; Yamano, Hidemasa; Tagami, Hirotaka; Suzuki, Toru; et al.

no journal, , 

In order to clarify the characteristics of debris bed behavior in the post accident heat removal phase in the core disruptive accidents of FBR, an experimental study to simulate the coolant boiling in debris bed by gas injection from the bottom of the bed and basic knowledge on the self-leveling characteristic for large vapor velocity was obtained.

Development of assessment method to evaluate the material relocation behavior in the core disruptive accident of FBR, 1; Development program and the development of the evaluation method of fuel escape behavior

Tobita, Yoshiharu; Kamiyama, Kenji; Suzuki, Toru; Matsuba, Kenichi; Tagami, Hirotaka; Yamano, Hidemasa; Morita, Koji*; Guo, L.*; Zhang, B.*

no journal, , 

The development program to develop the assessment methodology to analyze the fuel escape behavior and self-leveling behavior, which can be applicable to the design study and safety evaluation, and the progress of the development of analysis methodology of fuel escape behavior from core are presented.