TUBA (thermo-phoresis and diffusiophoresis) programme included experiments represented conditions expected in the SG tubes. Laminar flow was used in TUBA tests (TUBA-T: thermophoresis and TUBA-D: diffusiophoresis & thermo-diffusiophoresis).
In case of prolonged loss of cooling accident, the fuel rods of the core of a pressurized water reactor (PWR) will be damaged, and will collapse to form what is called a "debris bed", i.e.