Numerical simulation for the control rod assembly drop time evaluation in a LFR.

Area of Science:

• Nuclear Engineering
• Computational Fluid Dynamics (CFD)
• Reactor Safety

Background:

• Scram events require rapid Control Rod Assembly (CRA) insertion to shut down nuclear reactors.
• Accurate simulation of CRA dynamics is essential for ensuring reactor safety and optimizing design.

Purpose of the Study:

• To investigate the dynamics of Control Rod Assembly (CRA) drop in a lead-based research reactor using Computational Fluid Dynamics (CFD).
• To analyze the influence of fluid properties and CRA mass on the drop time during scram events.

Main Methods:

• Development of a 3D CFD model for the CRA within a lead-bismuth eutectic (LBE) filled guide tube.
• Application of averaged Navier-Stokes equations coupled with a dynamic mesh and a rigid body Fluid-Structure Interaction (FSI) method.
• Validation of the CFD model against existing literature data.

Main Results:

• The CFD model demonstrated applicability and reliability in simulating CRA drop dynamics.
• Lead-bismuth eutectic (LBE) coolant's high density was identified as the primary factor affecting CRA drop time.
• Increased CRA mass was found to reduce drop time due to enhanced driving force.

Conclusions:

• The employed CFD methodology provides a reliable approach for predicting CRA drop parameters.
• Findings offer valuable reference data for the design and modification of CRA and their drive mechanisms for enhanced reactor safety.