SMR startup simulation (outdated)

Overview

In order to test and demonstrate the time dependent calculation capabilities of the Kraken framework in a reasonably realistic context, a time dependent simulation was conducted of the initial rise to power of a small modular reactor (SMR) core.

The modelled SMR is the same 37 assembly Er-UO₂ fuelled core that has been previously used for the demonstration of the depletion capabilities of Kraken.

The transient starts from critical hot zero power (HZP) conditions (actually from 1 % power level) with all control rod banks at approximately 38 % insertion. The boron concentration in the coolant corresponds to the critical boron at all rods out (ARO) hot full power (HFP) conditions. The control rods are withdrawn from the core in a stepwise manner over 38 hours to allow for the accumulation of xenon in the core. To reformulate the simulation setup:

• Evaluate (in a time-independent simulation) critical boron at hot full power all rods out conditions with convergence in
  • Neutronics
  • Thermal hydraulics
  • Fuel temperature
  • Xenon
• Using that critical boron, evaluate (in a time-independent simulation) critical control rod position at 1 % power level with convergence in
  • Neutronics
  • Thermal hydraulics
  • Fuel temperature
  • Xenon
• Save initial conditions from the 1 % power level time-independent calculation.
• Start a time dependent simulation from 1 % power level and slowly withdraw the control rods fully from the core.

If the time-independent and time-dependent calculation methodologies produce equivalent steady state solutions and have been correctly implemented, the simulation should (in the end) end up in the same state as the time-independent HFP ARO calculation.