Summary of the Experiments:
The Power Reactor and Nuclear Fuel Development Corporation (PNC) conducted several experiments to study thermal-hydraulic behaviors in Liquid Metal Fast Breeder Reactors (LMFBRs). These experiments aimed to understand various flow phenomena under normal and transient conditions, including mixed convection, thermal striping, and vortex dynamics. Key areas of investigation included the penetration flow of cold coolant, thermal mixing of jets, and heat transfer in pin bundle geometries. The experiments utilized ultrasonic Doppler velocimetry (UVP) to achieve precise velocity measurements in water and liquid metals.
UVP-DUO Usage:
The UVP-DUO was integral in measuring velocity profiles in the experimental setups. The transducers were used to capture detailed flow dynamics in various configurations. Key setup parameters for the UVP-DUO included:
- Ultrasonic Frequency: 4 MHz
- Transducer Placement: Depending on the experiment, transducers were positioned to measure vertical and horizontal velocity profiles.
- Working Fluids: Water and liquid sodium were used in different experiments.
- Temperature Range: Measurements in sodium were conducted up to 300°C.
Results of the Experiments and How UVP-DUO Contributed:
1. Penetration Flow under Mixed Convection Conditions:
- UVP-DUO measured the velocity profiles of cold coolant penetrating into upward-flowing warmer coolant.
- Results showed the formation and penetration depth of the cold flow, providing insights into the local balance of inertial and buoyant forces.
2. Thermal Striping:
- UVP-DUO captured the velocity profiles of a cold jet surrounded by two hot jets, simulating thermal striping.
- Measurements revealed the extent of thermal mixing and the impact on reactor components.
3. Sodium Pipe Flow:
- UVP-DUO was used to measure velocity profiles in a sodium loop at high temperatures.
- The experiment demonstrated that velocity profiles could be measured accurately with sufficient tracer impurities, even at 300°C.
4. Vortex Dynamics in Water:
- UVP-DUO measured the velocity field associated with vortices generated near structural components.
- Data showed how energetic vortices could potentially entrain cover gas into the reactor's circulation loop.
5. Convective Heat Transfer in Pin Bundle Geometries:
- UVP-DUO measured local convective heat transfer in sub-channel and pin bundle configurations.
- Results indicated the impact of flow blockages and swirling flows on heat transfer efficiency.
6. Inter-Wrapper Flow and Heat Transfer:
- UVP-DUO measured convective heat transfer among fuel pin wrappers.
- The experiment quantified the heat removal capability due to inter-wrapper flow, contributing to the overall cooling efficiency of the reactor.
Overall, the UVP-DUO provided high-precision velocity measurements that were crucial for understanding complex thermal-hydraulic behaviors in LMFBRs. These measurements enabled detailed analysis and validation of flow dynamics, contributing significantly to the safe and efficient design of reactor components and cooling systems. The study highlights the effectiveness of UVP-DUO in advancing the knowledge of fluid mechanics in nuclear engineering applications.
How UVP-DUO Helped to Investigate Thermal-Hydraulic Phenomena in Liquid Metal Fast Breeder Reactors (1996)