Validation and Extension of a Correlation for Predicting Onset of Nucleate Boiling in Plate-Type Research Reactors

Abstract

This paper reports on the heat flux that leads to onset of nucleate boiling q{sub ONB} which is an important quantity for plate-type research reactors since it is frequently used as a thermal design constraint and also indicates the transition point from single- to two-phase heat removal in transient analyses. Recent experimental work has shown that q{sub ONB} can be sensitive to both channel gap size d and flow velocity u under laminar, upward flow conditions that are encountered in such reactors under natural-convection core cooling. New experimental data are presented to test the validity of the correlation proposed from the results of the previous work in extended d and local pressure p ranges. The correlation predicts the new experimental data for mixed or pure buoyancy-driven upward flows in 2.0 {le} d {le} 5.0 mm channels with 0.03 {le} u {le} 0.16 m/s and 1.05 {times} 10{sup 5} {le} p {le} 1.70 {times} 10{sup 5} Pa within 25%. The new d range covers almost all the existing and planned plate-type research reactors. The p range extends the applicability of the correlation to the analysis of a number of accident scenarios in open-pool reactors with power levels up to 5 tomore » 10 MW, such as partial loss of pool water or coolant pump trip.« less