UPTF results with respect to selected reactor safety issues

The full scale Upper Plenum Test Facility (UPTF) results are discussed with respect to certain important reactor safety issues: emergency core coolant (ECC) bypass, liquid de-entrainment as related to steam binding, hot leg countercurrent flow limit (CCFL) as related to a small-break loss-of-coolant accident (SBLOCA), ECC and primary coolant mixing as related to pressurized thermal shock concern, and steam-ECC interaction in the loop. In all of these issues the UPTF results played a primary role toward resolving them. Being full scale, the UPTF is particularly useful in resolving scaling issues. The ECC bypass was much less than that predicted by the correlations developed from small-scale test results. De-entrainment in the upper plenum, steam generator inlet plena, and hot legs was significant enough to result in a substantial decrease in peak clad temperatures. The hot leg CCFL data and the fluid mixing tests confirmed the previous favorable results of small-scale tests. The steam-ECC interaction tests also showed that serious water hammer occurrence following ECC injection was less likely than suggested by smaller scale test results