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NC STATE UNIVERSITY NUCLEAR ENGINEERIG DEPARTMENT

NC STATE UNIVERSITY NUCLEAR ENGINEERIG DEPARTMENT CENTER FOR ENGINEERING APPLICATIONS OF RADIOISOTOPES RADIOACTIVE PARTICLE TRACKING IN PEBBLE BED REACTORS By Prof. R. P. Gardner and Ashraf Shehata A R E C TOPICS Introduction Review of RPT Techniques

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NC STATE UNIVERSITY NUCLEAR ENGINEERIG DEPARTMENT

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  1. NC STATE UNIVERSITY NUCLEAR ENGINEERIG DEPARTMENT CENTER FOR ENGINEERING APPLICATIONS OF RADIOISOTOPES RADIOACTIVE PARTICLE TRACKING IN PEBBLE BED REACTORS By Prof. R. P. Gardner and Ashraf Shehata A R E C

  2. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • The Nonlinear Inverse Analysis Approach • Monte Carlo Simulated Results • Experimental Results • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  3. INTRODUCTION • ORIGIN:Developed Primarily by Chemical • Engineers • USES:Flow Characterization of Chemical • and Mineral Processes • EXPECTATIONS: • Potential for Benchmarking CFD Calculations • Potential for Combining RTD and CFD • Potential for Flow Characterization and Mapping of Fuel Pebbles In a Pebble Bed Reactor • Potential for Combining Flow Characterization andResidence Time Distribution Calculations for optimized Fuel Cycles A R E C

  4. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Semi-Empirical Modeling • Monte Carlo Simulated Modeling • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  5. REVIEW OF PREVIOUS WORK • Extensive Review by Larachi, Chaouki, Kennedy, and Dudukovic: Chap.11: RadioactiveParticle Tracking in Multiphase Reactors: Principles and Applications in NON-INVASIVE MONITORING OF MULTIPHASE FLOWS, Elsevier Science, 1996 • Linearization of Inverse Solution • First “full-flow-field” particle velocities in multiphase reactors were by Kondukov et al. (1964), Borlai et al. (1967), and van Velzen et al. (1974) A R E C

  6. REVIEW OF PREVIOUS WORK • University of Illinois System, 1983 • Florida Atlantic University, 1990 • Washington University, 1990 • Ecole Polytechnique of Montreal, 1994 • Gatt at AAEC Research Establishment, 1977, Flow of Individual Pebbles in Cylindrical Vessels, Nuclear Engineering and Design, 42, 265-275 – missed in review A R E C

  7. REVIEW OF PREVIOUS WORK • CURRENT APPROACHES: • Based Primarily on “TOMOGRAPHIC” Imaging, in which an Array of Detectors is Assembled Around the System. A R E C

  8. REVIEW OF PREVIOUS WORK GATT, 1 A R E C

  9. REVIEW OF PREVIOUS WORK GATT, 2 A R E C

  10. REVIEW OF PREVIOUS WORK GATT, 3 A R E C

  11. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Semi-Empirical Modeling • Monte Carlo Simulated Modeling • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  12. PREVIOUS WORK ON RPT at CEAR Radioactive Particle Tracking in a Ball Mill A R E C

  13. PREVIOUS WORK ON RPT at CEAR Top View 10 cm 4 cm 6 cm 6 cm 10 cm Sources Detector 1 Detector 3 25.4 cm 25.5 cm 5 cm 5 cm Detector 2 Detector 4 Four Detectors, Dual Energy RPT Experiment A R E C

  14. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Semi-Empirical Modeling • Monte Carlo Simulated Modeling • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  15. PREVIOUS WORK ON RPT at CEAR The Dual Energy Approach • A radioactive particle with two “clean” energies is used – Co-60, Sc-46, Na-24 • Either two SCA’s with a “window” in each or an MCA with two ROI’s can be used for each detector –> doubling the data available from the same number of detectors • The additional data can be placed directly into the least-squares analysis A R E C

  16. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Semi-Empirical Modeling • Monte Carlo Simulated Modeling • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  17. PREVIOUS WORK ON RPT at CEAR Y Detector 4 X Z Particle Trajectory Radioactive Particle Detector 3 Detector 1 Detector 2 Experimental Results: Experiment Schematic • System Chosen for Study was Ball Mill • Four 2” X 2” NaI Detectors were Used • A Sparrow 4-channel system with MCA’s was Used A R E C

  18. PREVIOUS WORK ON RPT at CEAR Y Detector 4 X Z Particle Trajectory Radioactive Particle Detector 3 Detector 1 Detector 2 Experimental Results: Responses For The Four Detectors A R E C

  19. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Semi-Empirical Modeling • Monte Carlo Simulated Modeling • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  20. PREVIOUS WORK ON RPT at CEAR Experimental Results: Analytical Nonlinear Model Where; Ci=total photopeak counts of ith detector, ri=distance from tracer to ith detector, R=attenuation of mill wall and charge, SR=distance traveled in wall and charge, D =attenuation in detector, SD=distance traveled in detector, B = background, A = a constant proportional to the source intensity. A R E C

  21. PREVIOUS WORK ON RPT at CEAR Experimental Results: Measurements Vs. Model A R E C

  22. PREVIOUS WORK ON RPT at CEAR Experimental Results: Measurements Vs. Model A R E C

  23. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Inverse Analysis Approach • Monte Carlo Simulated Results • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  24. PREVIOUS WORK ON RPT at CEAR Monte Carlo Simulated Results: • The Expected Value Approach Was Used • One can Force Every Gamma Ray to be Detected so only a few are required • Needed Limiting Subtended Angles to Cylinder: Gardner, Choi, Mickael, Yacout, Jin, and Verghese, 1987, Algorithms for Forcing Scattered Radiation to Spherical, Planar Circular, and Right Circular Cylindrical Detectors for Monte Carlo Simulation, Nuclear Science and Engineering, 95, 245-256 A R E C

  25. PREVIOUS WORK ON RPT at CEAR Monte Carlo Simulated Results: Schematic of a NaI Detector in an Attenuating Column A R E C

  26. PREVIOUS WORK ON RPT at CEAR Monte Carlo Simulated Results: Need Limiting Angle !! A R E C

  27. PREVIOUS WORK ON RPT at CEAR Monte Carlo Simulated Results: Monte Carlo Map of Counting Rates of one Detector VS. Tracer Position A R E C

  28. PREVIOUS WORK ON RPT at CEAR Monte Carlo Simulated Results: Monte Carlo Simulated Vs. Experimental Results A R E C

  29. TOPICS • Introduction • Introduction To Pebble Bed Reactor • Review of Previous Work on RPT • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • Monte Carlo Simulated Results • The Nonlinear Inverse Analysis Approach • Critique on Previous Work • An Alternative Approach for RPT • Discussion and Conclusions A R E C

  30. CRITIQUE ON PREVIOUS WORK • Discrepancies Between Measurements and Monte Carlo Modeling: • This is Mainly Due to Information Distortion Due to Counting Losses Typical to High CountingRate Systems (Dead Time, Pulse Pileup,..) A R E C

  31. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Inverse Analysis Approach • Monte Carlo Simulated Results • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  32. MODULAR HIGH TEMPERATURE PEBBLE BED RECTOR • Helium Cooled • “Indirect” Cycle • 8 % Enriched Fuel • Can be Built in • 2 Years • Factory Built • Site Assembled • On-line Refueling • Highly Modular • (Modules added to meet demand) • High Burnup >90,000 Mwd/MT • Direct Disposal of High Level Waste A R E C

  33. MODULAR HIGH TEMPERATURE PEBBLE BED RECTOR For A 110 MWe: • 360,000 pebbles in core • about 3,000 pebbles handled • by Fuel Handling System Daily • about 350 discarded daily • one pebble discharged every • 30 seconds • average pebble cycles through • core 15 times • Fuel handling most maintenance-intensive • part of plant German AVR Pebble Bed Reactor A R E C

  34. MODULAR HIGH TEMPERATURE PEBBLE BED RECTOR TRISO Fuel Particle; (Microsphere) • 0.9mm diameter • ~ 11,000 in every pebble • 109 microspheres in core • Fission products retained inside microsphere • TRISO acts as a pressure vessel A R E C

  35. MODULAR HIGH TEMPERATURE PEBBLE BED RECTOR International Activities: • China - 10 Mwth Pebble Bed - 2000 critical • Japan - 40 Mwth Prismatic • South Africa - 250 Mwth Pebble Bed- 2003 • Russia - 330 Mwe - Pu Burner Prismatic 2007 • Netherlands - small industrial Pebble • Germany 300 Mwe Pebble Bed (Shut down) • MIT - 250 Mwth - Intermediate Heat Exch. A R E C

  36. MODULAR HIGH TEMPERATURE PEBBLE BED RECTOR Application Of (RPT) To Pebble Tracking: • Excessive Time Spent In Parts Of The Bed Could Result In Severe Irradiation And Thermal Damage To The Pebble • The Feasibility Of The Recycling Of Fuel Pebbles In a Pebble Bed Reactor Depends On a satisfactory Pebble Flow Through The Vessel, Its Outlet, and The Pebble Extractor • So It Is Important To Know Pebble Pathways And Relative Velocities Through The Bed • There Is Need For technique To study the Dynamics Of Pebbles In a Pebble Bed Reactor • One Can Track pebbles In a Scaled Prototype Pebble Bed Reactor (RPT) A R E C

  37. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Inverse Analysis Approach • Monte Carlo Simulated Results • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  38. CRITIQUE ON PREVIOUS WORK • Large Number of Detectors is Needed For Reasonably Accurate Tracking : • Due to Inherent uncertainties Associated With Linear/Nonlinear Map Search, As much As Possible Redundant Information is Necessary For Sufficiently Accurate Particle Tracking. Thus a Large Number of Detectors is Needed Depending on the Size of The System To Be Investigated A R E C

  39. CRITIQUE ON PREVIOUS WORK • Expected Modeling Difficulties In Stochastic Heterogeneous Systems, Such As Pebble Bed Reactors. • Randomly Distributed Pebbles May Produce Large Amount of Contrast in Attenuation Between Different Particle Positions Corresponding To Same Distance From The Detector In Question, Specially At The Container Wall Region A R E C

  40. TOPICS • Introduction • Review of RPT Techniques • Review of Previous Work on RPT at CEAR • The Dual Energy Approach • Experimental Results • The Nonlinear Inverse Analysis Approach • Monte Carlo Simulated Results • Introduction To Pebble Bed Reactor • Critique on Previous Work • An Alternative Approach for RPT A R E C

  41. ALTERNATIVE APPROACH FOR RPT OBJECTIVES • Investigate An Improved RPT Approach to Overcome Current Approach Limitations : • Eliminate Information Distortion Due to Counting Losses Typical to High CountingRate Systems (Dead Time, Pulse Pileup,..) • Reduce number of Detectors Needed • Overcome Modeling Difficulties of Heterogeneous Stochastic Attenuating Media Such as Pebble Bed Reactors A R E C

  42. ALTERNATIVE APPROACH FOR RPT OBJECTIVES • Investigate An Improved RPT Approach to Overcome Current Approach Limitations : • Eliminate Information Distortion Due to Counting Losses Typical to High CountingRate Systems (Dead Time, Pulse Pileup,..) • Reduce number of Detectors Needed • Overcome Modeling Difficulties of Heterogeneous Stochastic Attenuating Media Such as Pebble Bed Reactors A R E C

  43. ALTERNATIVE APPROACH FOR RPT Overview of The Concept • The Concept is Based on Dynamic Motion Control of a Cluster of Three Very Well CollimatedDetectors • The Detectors are Mounted on a Platform Whose Height Can be Varied • The Center Detector (With a Horizontal Slit) is Used to Directly Establish the Vertical Position of the Tracer A R E C

  44. ALTERNATIVE APPROACH FOR RPT Overview of The Concept • The Two Outer Detectors are Independently Rotated To Align With The Tracer (Line of Sight Position) • The Angles 1 and 2 are Instantaneously Recorded Providing The Two Cylindrical Coordinates r and  A R E C

  45. ALTERNATIVE APPROACH FOR RPT Coordinates Determination A R E C

  46. ALTERNATIVE APPROACH FOR RPT Coordinates Determination A R E C

  47. ALTERNATIVE APPROACH FOR RPT Coordinates Determination A R E C

  48. ALTERNATIVE APPROACH FOR RPT Sensitivity of Determined Coordinates To Measured Angles A R E C

  49. ALTERNATIVE APPROACH FOR RPT Detector Response to Particle Position A R E C

  50. ALTERNATIVE APPROACH FOR RPT Detector Response to Particle Position • The Accuracy and Resolution of the • Particle Positions are determined Primarily • by Two Factors: • How Well Resolved • Detector Response • Maximum. • The Precession and Accuracy of the Physical Dimensions of the Tracking System. A R E C

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