Burnup computations of online-refueling process for pebble-bed reactors using layer-mixed-shell fuel movement model.

Area of Science:

• Nuclear Engineering
• Computational Physics
• Reactor Design

Background:

• Pebble-bed reactors (PBRs) offer efficient online refueling, reducing downtime and increasing fuel burnup.
• Simulating dynamic fuel movement in PBRs presents significant computational challenges.
• Accurate modeling is essential for optimizing PBR performance and safety.

Purpose of the Study:

• To develop a dynamic simulation model for PBR online refueling.
• To reduce computational time for PBR simulations.
• To accurately predict fuel burnup characteristics during refueling.

Main Methods:

• Utilized MCNPX 2.7.0 with the ENDF/B-VII nuclear data library.
• Developed a layer-mixed-shell fuel movement model within fuel channels.
• Simulated the once-through-then-out (OTTO) fuel loading scenario for the HTR-10 design.

Main Results:

• Achieved an equilibrium fuel cycle with stable core characteristics.
• Reached a discharged burnup of approximately 80 GWd/tHM, meeting HTR-10 design specifications.
• The model accurately predicted burnup in both radial and axial directions.

Conclusions:

• The proposed layer-mixed-shell model enhances simulation accuracy for PBR refueling.
• The model successfully balances computational efficiency with precise prediction of burnup.
• This approach provides a more realistic simulation of the HTR-10 refueling process.