Motivation

Advanced Gas Reactors (AGRs)•The advancement and commercialization of nuclear energy produced by advanced gas reactors (AGRs) (spouted bed) is dependent on Tri-isotropic (TRISO) fuel particle coating step via chemical vapor deposition in gas-solid fluidized spouted beds•The acceptable level of defective coated particles is essentially zero•The quality of nuclear fuel particles produced is strongly impacted by the hydrodynamics of the spouted bed, solids flow field and flow regime characteristics•Unfortunately, the current spouted fluidized bed coating technology and “scale-up” relies on trial and error and is based on empirical approaches•Accordingly, fundamental understanding of the underlying phenomena of the spouted bed TRISO coater using advanced diagnostic techniques is essential

Objectives• Hydrodynamic investigation of solid particles’

and gas holdup distribution

• Assessing and comparison of results obtained by different advanced measurement techniques – optical probe and γ-ray computational tomography (CT)

• Identification of match and mismatch hydrodynamic conditions

• Evaluation of reported dimensionless groups for scale-up of spouted bed reactors

• Investigation of the effects of scale, design and operating conditions on dimensionless groups, cross-sectional solid and gas holdup profiles

Future plan• Performing of further experiments in order to validate the conditions of hydrodynamic similarity and

dissimilarity, by changing the size of reactor, inlet gas velocity, solid material and other parameters

• Implementation of the new optical system that will enable not only measurement of solid holdup distribution but also measurement of solid particle velocity

• Complementing the investigation and measurement with pressure transducers measurement

• Investigation of the effect of the selected conditions (match and mismatch) on the pressure signals and compare the findings with the results obtained by optical probe technique and computational tomography

• Evaluating the approach for the development of the on-line measurement technique based on nuclear gauge densitometry (NGD)

Fuel kernel -provide fission energy

Buffer layer - attenuates fission product recoils from kernel

- provides space for the fission gases

Inner pyrocarbon (IPyC) - traps the fission gases inside the particle

- protects kernel from clorine- during SiC deposition

- provides support for SiC

Silicon carbide (SiC)- the primary component, the strongest layer

- impervious to gaseous fission products

Outer pyrocarbon (OPyC) - protects SiC from surroundings

- holds SiC in compression

Experimental Setup• A small scale fluidized spouted bed column with 6 inches diameter

• Solid particles: glass beads 2 mm diameter, 2.5 g/cc density

• Gas phase: air

• Distributor :inlet orifice of 0.5 inch i.d. and 20% open area

• Bed height of 32.5 cm and an inlet pressure of 80 psig

• Operating gas velocity Ug=1.09 m/s

• Ten axial positions where an optical probe can be inserted into the column, in order to determine the solid concentration

• Axial positions are separated by 47.24 mm in order to create a complete concentration profile in the spouted bed

• Measure at six radial positions at each axial position

Advancing the Fundamental Understanding and Scale-up of Spouted Bed TRISO CoatersVesna Havran, Josh Grimes, Fadha Ahmed, and Muthanna Al-Dahhan

TRISO particle

CHEMICAL REACTION ENGINEERING LABORATORY (CREL)

Computational Tomography

• Time averaged solid and gas holdup cross-sectional distribution• Measure attenuation coefficient on the basis of Beer Lambert’s law:

• 7 out of 11 NaI- detectors were used• Source: Cs-137 of 187 mCi

Optical probe

• Local solid and gas holdup measurements based on backscattering of light• Three fibers, one receiver and two detectors aligned in a straight line• 1/8 inch diameter tubing, 600 microns fiber diameter• Distance between detectors 2mm

Nuclear power is the most environmentally benign way of producing electricity on a large scale. Therefore the increasing importance of nuclear power in meeting energy needs while achieving security of supply and minimizing carbon dioxide emissions.

Background• Spouted fluidized beds are very efficient in contacting gases and

coarser particles. Therefore, they have been applied to a wide variety of processes including: coating, granulation, drying, coal gasification, catalytic reactions, and more.

• A jet of air penetrates the bed of particles, creating a central spout zone, a fountain about the spout, and an annulus surrounding the spout.

• Different flow regimes and characteristics can be obtained with minor variations in geometry or operating conditions

• Existing scale-up approaches based on hydrodynamic and geometrical similarity do not take into account two additional non-dimensional terms:

- interfacial angle of particle (), or internal friction angle

- loose packed voidage ()that need to be considered in order to achieve mechanical

similarity.

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