Analysis of the pebble burnup profile in a pebble-bed nuclear reactor

•Flow in a pebble-bed reactor is simulated using the discrete-element method.•Fuel burnup profiles are made by considering each pebble individually.•Burnup profiles in the core and at the exit pipe are analyzed in detail.•The complete pebble recycling and discharging procedure is modeled.•Flow and burnup profiles depend on a complex interplay of pebble and wall friction.