Experimental and Computational Analysis of NEAMS Pebble Bed Reactors

Technical Report · Fri Dec 20 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1580655· OSTI ID:1580655

Ugaz, Victor ^[1]; Hassan, Yassin ^[2]; Nguyen, Thien ^[2]; Merzari, Elia ^[3]

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1. Texas A & M Univ., College Station, TX (United States); Texas A&M University
2. Texas A & M Univ., College Station, TX (United States)
3. Argonne National Lab. (ANL), Argonne, IL (United States)

The Advanced High-Temperature Pebble Bed Reactor concept leverages a particle-based fuel format consisting of discrete spherical graphite pebbles arrayed in a packed bed architecture. Thermal regulation achieved via flow of gas (e.g., helium) or liquid (e.g., molten salt) coolants through the void spaces between pebbles in the bed (characteristic pebble diameters: ~ 6 cm, gas cooled; ~ 3 cm, liquid cooled). This design is of interest owing to inherent advantages including passive safety features and highly efficient heat transfer characteristics that enable high power densities to be achieved. Fully leveraging these advantages requires a fundamental understanding of the complex coolant flow structure within the pebble-shaped fuel bed. Unfortunately, complexities associated with non-invasively probing the micro-scale flow phenomena within the complex network of void spaces between pebbles have hindered efforts to characterize the underlying transport phenomena. Without this fundamental foundation, it becomes challenging to rationally construct macroscopic transport models based upon volume averages of micro-scale parameters that accurately capture the observed flow behavior. Consequently, this lack of fundamental knowledge has limited previous work to coarse comparisons between theory and extremely limited experimental data. Moreover, these comparisons have been made only in terms of integral or macroscopic results. Therefore, multipoint measurements with a high level of spatial and temporal resolution are critically needed to fully map the complex flow patterns and to provide data at high spatial density to permit accurate volume averaging in the pebble bed. For this project, we performed a coordinated experimental and computational effort to quantitatively map the full-field velocity and temperature fields in the interstitial spaces within the pebble bed. The major accomplishments of this project included the important knowledge acquired for the flow mixing and heat transfer in the interstitial pore scales, the effects of flow mixing in the near-wall and far-wall regions, and the by-pass flows of pebble bed systems. The produced high-resolution experimental data (not broadly available in existing literature) were then used for the numerical studies enabling the refinement and validation of standard simulation tools (Nek5000).

• Research Organization: Texas A & M Univ., College Station, TX (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• Contributing Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• DOE Contract Number: NE0008550
• OSTI ID: 1580655
• Report Number(s): DOE-TAMU--16–10603-Final-Technical-Report
• Country of Publication: United States
• Language: English

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