Evaluation of predictability of multiple CHF events

The phenomenon of multiple CHF events in rod bundle heat transfer tests, referring to the occurrence of CHF on more than one rod or at more than one location on one rod is examined. The adequacy CE-1, BandW-2, and Columbia subchannel CHF correlations in predicting higher order CHF events is ascertained based on local coolant conditions obtained with the COBRA IIIC sub channel code. The data from three sets of tests simulating both PWR and BWR reactor cores obtained at the Heat Transfer Research Facility of Columbia University are studied using a combination of statistical analyses and parametric studies. Results show that: 1) the characteristic behavior of the higher rank CHF are essentially the same as those of the first CHF; and 2) the presently available subchannel CHF correlations predict the CHF events of higher rank with the same degree of accuracy as the first CHF