Experimental Determination of Sodium Superheat Employing LMFBR Simulation Parameters

Sodium superheat experiments were performed in a forced convection facility employing system parameters in the range of interest for application to loop and pot-type liquid metal cooled fast breeder reactors. The test section was representative of a single reactor fuel element with sodium flowing vertically upward in an annulus heated indirectly from the inside wall only. Steady-state operating parameters prior to a flow coast down approach to boiling included: velocity, 17 fps; heat flux, 7 × 10⁵ Btu/hr-ft²; test section inlet, 600 deg F; test section outlet to plenum, 900 deg F; plenum, 15 psia at 900 deg F and 700 deg F. Other important system variables controlled included sodium inert gas content and system pressure-temperature history. The axial location of boiling initiation in the test section was measured. Five test series encompassing 33 test runs were performed. Applicable superheat results were compared to predictions of the pressure-temperature history model including inert gas effects.