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Raymond S. Troy, Robert V. Tompson, Jr., Tushar K. Ghosh and Sudarshan K.Loylalka Particulate Systems Research Center & Nuclear Science and Engineering.

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Presentation on theme: "Raymond S. Troy, Robert V. Tompson, Jr., Tushar K. Ghosh and Sudarshan K.Loylalka Particulate Systems Research Center & Nuclear Science and Engineering."— Presentation transcript:

1 Raymond S. Troy, Robert V. Tompson, Jr., Tushar K. Ghosh and Sudarshan K.Loylalka Particulate Systems Research Center & Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO 65211

2  Made up of about 400,000 pebbles  Online refueling  Fission potential measured when removed from reactor  Remain in cycle up to 6 years (~10 trips)

3 1. PBMR Ltd. http://www.pbmr.co.za/index.asp?Content=213&GState=Image&CatId=-1&Image=44&Page=1

4  As the reactor operates, the pebbles are in contact with each other, the fuel handling system, and reactor components (pressure vessel, etc.) and graphite dust is produced. For many reasons, information about this dust must be collected.  Our goal is to characterize graphite particles generated by fuel pebble abrasion

5  Safety  Modeling ▪ “the production of dust by fuel element abrasion and its effect on fission product transport…would complete a comprehensive model for the core release behavior under normal operating conditions 1.” ▪ Data provided to codes  Accident mitigation ▪ Amount of dust  Inhalation ▪ Cancer/dose calculations 1. http://www.iaea.org/inisnkm/nkm/aws/htgr/fulltext/29009817.pdf

6  Operation  Radioactivity levels ▪ Estimate radioactivity levels in the loop  Mechanical ▪ Clogs ▪ Length of pebble life  Re-suspension ▪ Depressurization of the loop may cause re-suspension of dust  Modeling of thermophoresis ▪ Uneven distribution of particles along loop 1. http://www.iaea.org/inisnkm/nkm/aws/htgr/fulltext/29009817.pdf

7  Size Distribution  Mean, Standard Deviation and Median calculated  Loading and rotational speed measured  SEM images of sample and abraded particles  Unbraded Surface roughness  BET surface area, pore analysis  Humidity and temperature in room

8 Our experimental apparatus allows us to control loading, atmosphere, rotation speed, graphite type and the shape of the graphite interface.

9  Measures particle size distributions in the diameter range 2.5 nm to 1000 nm  Pulls vacuum of 2.4 L/min and particles are drawn into the machine http://www.tsi.com/Scanning-Mobility-Particle-Sizer-Spectrometer-3936/

10 http://www.tsi.com/Aerodynamic-Particle-Sizer-Spectrometer-3321/  Measures particle size distributions in the diameter range 500 nm to 20,000 nm  Pulls vacuum of 5 L/min and particles are drawn into the machine

11  The loading between the two hemispheres is measured by a Mettler Toledo Scale, model number PBA 430, with an IND 560 readout having accuracy to 0.001 kg.  The rotational speed is determined by the machine’s preset speeds.

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13 Manufacturer:Graphtek LLC Method of Manufacturing:Isostatically Pressed Description: Isomolded, very fine grain, high strength, low ash graphite with superior oxidation resistance. PROPERTYUS VALUEMETRIC VALUE Density0.063lb/in 3 1.75gr/cm 3 Particle Size0.0015in0.00381cm Flexural Strength8570psi59.1mpa Compressive Strength14280psi98.5mpa Resistivity5.5ohm/in*10 -4 Hardness50scleroscope50 CTE2.1in/in °F*10 -6 3.8Microns/m °C Porosity13.2% % Thermal Conductivity52BTU/(h.ft 2 °F/ft)90W/(m 2. K/m) Ash0.01% %

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15  Samples were prepared  Machined inserts  The assembly was dismantled and cleaned  Background samples were taken  With graphite samples in cylinder  Machine was started  Loading set  Collection of data

16 Test No. Loading (kg) Rotational Speed (RPM) 1601500 2311500 3101500 422310

17 10 Kg and 1500 RPM

18 31 Kg 1500 RPM

19 56 Kg 1500 RPM

20 22 Kg 310 RPM

21 A) Before the test B) After the test

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24 626 m 2 gm −1 This is very high

25 Diameter of most of the pores is in the range of 10 to 60 Å.

26 Total cumulative pore volume was found to be 1.213 cm 3 gm −1. Porosity of the generated particle is about 68%.

27  Measured with a atomic force microscope (AFM)  Average Ra of pre abraded samples was 0.96 µm  The AFM did not have capability to measure post abrasion surface roughness (too rough)  We have a new method to measure surface roughness and this will not be an issue for future tests

28  The size distribution and the concentrations change with time  wear has a strong effect on particle generation rate as well as size, and physical/mathematical models for particle generation should account for the aging of the pebbles.  Time changes at what size particles are generated

29  Certainly, with different loadings, graphites, atmospheres, and rotational speeds the particle size distributions will change  models for particle generation will need to account for abrasive effects

30  Dry Air (to produce dusting effect)  Reactor grade graphite  Shape of interface (disk, point)  Sliding abrasion  Wear Rate  Statistical Fit of size distribution  Temperature and Humidity measurements inside chamber  Surface roughness before and after test

31  Questions?


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