Onset of significant void

Sc, local subcooling parameter OSV, onset of significant void ... 

DPST-88-886, "Comparison of the FLOWTRAN Predictions of the Onset of Significant Voiding (OSV) to Savannah River Heat Transfer Laboratory Subcooled Boiling How Instability Measurements, Part 1" (U), Rev. October 1988. 

For the FI phase, a conservative, test-coniFirmed value (References 6 through 9) of the Stanton Number is used to estimate the onset of significant voids (OSV) in a nominal fuel channel in downflow (Figure 2). The OSV criteria, which represents.a criteria by nonTexceptjph, is invariably a precursor to, and predictive indicator of, an impending.flow instability in the channel under nominal conditions. Power levels/limits associated with the nominal channel are subsequently reduced to statistically account for subchannel... 

Later, correlations for the onset of nucleate boiling (ONB) were used as the T/H criterion to predict the onset of flow instability (OFI) within the subchannels. For restart, a prototypic, experimentally-confirmed, bounding limit for the onset of significant voids (OSV) has been adopted as a precursor to FI. 

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