Critical gas velocity required for complete suspension of solid particles in solid-suspended bubble column with draught tube.

Journal of Nuclear Science and Technology

Tanaka

Gondai

et al. 2011

Studies on the self-leveling behavior in debris beds are crucial in the assessment of core-disruptive accidents (CDAs) that could occur in sodium-cooled fast reactors (SFRs). To clarify this behavior, a series of experiments have been performed in which nitrogen gas has been percolated uniformly through a particle bed. In these experiments, solid particles and water contained in a rectangular tank simulate respectively fuel debris and coolant. Based on the data obtained, an empirical model was developed to describe the transient variation in the bed inclination angle during the self-leveling process. Good agreement has been obtained between calculated and experimental values. Verification of the model has been confirmed through detailed analysis of the effects of experimental parameters such as particle size, particle density, and gas flow rate. Its applicability to extended conditions was further discussed by performing modeling simulations and comparing results against experimental data obtained from a larger-scale experimental system that employed a conventional boiling method. With further improvements, the model will be tested under more realistic reactor conditions and is expected to benefit future analyses and simulations of CDAs in SFRs.

Section: Development Of Empirical Modelmentioning

confidence: 99%

Experimental Studies and Empirical Models for the Transient Self-Leveling Behavior in Debris Bed

Journal of Nuclear Science and Technology

Tanaka

Gondai

et al. 2011

“…This thought is confirmable by several prior studies regarding the analysis of packed bed movement. For instance, Koide et al and Abraham et al experimentally studied the critical gas velocity (U gc ) required for the suspension of solid particles (or particle aggregates) in three-phase columns [27][28][29]. In their studies, column dimensions and shape, sparger design, and properties of the liquid and solid particles were observed to have a strong influence on U gc .…”

Section: Base Modelmentioning

confidence: 99%

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

Journal of Nuclear Science and Technology

Tagami

Yamano

et al. 2014

Studies on debris bed self-leveling behavior with non-spherical particles are crucial in the assessment of actual leveling behavior that could occur in core disruptive accident of sodium-cooled fast reactors. Although in our previous publications, a simple empirical model (based model), with its wide applicability confirmed over various experimental conditions, has been successfully advanced to predict the transient leveling behavior, up until now this model is restricted to calculations of debris bed of spherical particles. Focusing on this aspect, in this study a series of experiments using non-spherical particles was performed within a recently developed comparatively larger scale experimental facility. Based on the knowledge and data obtained, an extension scheme was suggested with the intention to extend the base model to cover the particle-shape influence. The proposed scheme principally consists of two parts -with one part for correcting the terminal velocity of a single non-spherical particle, which is the key parameter in our base model, and the other for representing the additional particle-particle interactions caused by the shaperelated parameters. Through detailed analyses, it is found that by coupling this scheme, good agreement between experimental and predicted results can be achieved for both spherical and non-spherical particles given current range of experimental conditions.

“…This thought is confirmable by several prior studies regarding the analysis of packed bed movement. For instance, Koide et al (1983Koide et al ( , 1984 and Abraham et al (1992) experimentally studied the critical gas velocity ( gc U ) required for the suspension of solid particles (or particle aggregates) in three-phase columns. In their studies, column dimensions and shape, sparger design and properties of the liquid and solid particles were observed to have a strong influence on gc U .…”

Section: Status Of Developing Empirical Approach 41 Base Modelmentioning

confidence: 99%

Experimental study and empirical model development for self-leveling behavior of debris bed using gas-injection

Mechanical Engineering Journal

Tagami

Yamano

et al. 2014

Studies on the self-leveling behavior of debris bed are crucial in the assessment of core disruptive accident (CDA) that could occur in sodium-cooled fast reactors (SFR). To clarify the mechanisms underlying this behavior, several series of experiments were elaborately designed and conducted within a variety of conditions in recent years, under the close collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). The current contribution, including knowledge from both experimental analyses and empirical model development, is focused on a recently developed comparatively larger-scale experimental facility using gas-injection to simulate the coolant boiling. Compared to the previous investigations, this facility can achieve a much wider range of gas velocities (presently up to a flow rate of around 300 L/min). Based on the experimental observation and quantitative data obtained, influence of various experimental parameters, including gas flow rate (~ 300 L/min), water depth (180 mm and 400 mm), bed volume (3 ~ 7 L), particle size (1 ~ 6 mm), particle density (beads of alumina, zirconia and stainless steel) along with particle shape (spherical and non-spherical) on the leveling is checked and compared. As for the empirical model development, aside from a base model which is restricted to predictions of spherical particles, the status of potential considerations on how to cover more realistic conditions (esp. debris beds formed with non-spherical particles), is also presented and discussed. This work, which gives a large palette of favorable data for a better understanding and an improved estimation of CDAs in SFRs, is expected to benefit future analyses and verifications of computer models developed in advanced fast reactor safety analysis codes.